"My spouse, my cousin" math quiz

EDIT: typo in poll question "uncle/nice" should read "uncle/niece"




UK news article: It's time to confront this taboo: First cousin marriages in Muslim communities are putting hundreds of children at risk

This issue will become more of an issue in the USA, as immigration from countries that encourage first cousin marriage increase in the USA

Quote: Daily Mail

The man wept as he told how his beautiful, dark-eyed child died in a hospital cot with medical tubes snaking from his frail body as nurses fought unsuccessfully to save him. Sick with pneumonia, the two-year-old gave up the battle for life. A rare tragedy, you might think, in modern Britain, with all the advances of medical science. But in the terraced streets of Bradford, Yorkshire, a child’s death is anything but rare. At the boy’s inquest, coroner Mark Hinchliffe said Hamza Rehman had died because his Pakistan-born parents (shopkeeper Abdul and housewife Rozina) are first cousins.
...
While British Pakistanis account for three per cent of the births in this country, they are responsible for 33 per cent of the 15,000 to 20,000 children born each year with genetic defects.
The vast majority of problems are caused by recessive gene disorders, according to London’s Genetic Interest Group, which advises affected families.

One of the issues with consanguinity is that there are residual effects down the generation.
Define full first cousins as two people with both a grandfather and grandmother in common (i.e. a normal cousin relationship). There are also half first cousins, and double first cousins. But ignore this complication momentarily.

Given the high rate of full first cousin marriages among this group of people, the question is:

If you are the child of a full first cousin marriage, and both your parents are also the children of full first cousin marriages, and all four of your grandparents are the children of full first cousin marriages, and so on, it is the equivalent of being born to ... (poll question)?

Mathematically, I leave the question at infinite generations, but for practical purposes, two generations would be very nearly equivalent to infinite generations.

Quote: Daily Mail

One young mother, calling herself by the Pakistani name of Shenzah, wrote recently: ‘I have a huge difficulty. I am married to a first cousin. My parents and my husband’s parents were also married to their first cousins.
‘Now I have one daughter with lots of defects and the doctor is sure it is due to these marriages.

Secondary political question- Unlike the UK, the legality of first cousin marriage is decided by state law in the USA. In some states it is illegal, other states require genetic counseling, some permit it if both people are infertile or past child bearing age, but many states do not address the issue. We have a relatively small population of children born to first cousin marriages. Presumably first cousins who want to marry simply need to establish residency in another state, then marry, and they can later return to their original state. A "pre-emptive strike" would be to prohibit first cousin marriages across the country, and make it a condition of immigration that first cousin couples divorce if they choose to immigrate. That would still leave the stickier question of existing children, or children later born out of wedlock (since the couple may still consider themselves married under Islamic law, and only divorced under American civil law).

or

Leave it to personal choice. Treat the children who may suffer from debilitating painful disease. Remember that Pakistan alone is predicted to have 291 million people by the year 2050 (almost the present population of the USA) in an area roughly twice the size of California. They are also not the only country that practices first cousin marriage. Some estimates are as high as 20% of the world's marriages.

Quote: Factoid

Britain maintained a small but stable proportion of cousin marriages for centuries, with proportions in 1875 estimated by George Darwin at 3.5 percent for the middle classes and 4.5 percent for the nobility. Obviously this percentage has declined significantly in the 20th century among native born Britons.

In past centuries, the genetic risk of first cousin marriages was somewhat balanced out by the much earlier age of childbearing. Motherhood in the late 30's has somewhat the same level of risk as having a child born to first cousins. In any event, the other risks to the health of young children was so overwhelming in earlier centuries, that genetic disease was not a huge consideration.

CAVEAT: We are talking about risk reduction. Not all children of first cousin marriages have genetic disease. I am not advocating any formal program to ostracize existing children of first cousin marriages.

I know I read a couple years ago that 1st cousin marriages are now deemed safe.

Quote: EvenBob

I know I read a couple years ago that 1st cousin marriages are now deemed safe.

"Safe" is not the correct word. No European country prohibits first cousin marriages, and they can legally marry in Canada, Mexico and many other countries. It is perceived as with the acceptable parameters of free will. Advocacy groups argue that late age childbirth is just as dangerous, and the state considers that to be a personal choice. No one is talking about forbidding women from having a child after a certain age. What would be the punishment.

The recent court decision that Louisiana had no right to rule an Iranian first cousin marriage was illegal just because it is illegal in Louisiana was closely watched by gay marriage advocates. It may form the basis for gay "out of state" or "foreign marriages" to be honored in states that prohibit such unions.

I hope someone tries the math.

Quote: pacomartin

"Safe" is not the correct word. No European country prohibits first cousin marriages

Without first cousin marriages, European royalty would have been out of business. Hawaiian royalty used to marry their brothers and sisters. Oh boy..

Quote: EvenBob

Without first cousin marriages, European royalty would have been out of business. Hawaiian royalty used to marry their brothers and sisters. Oh boy..

Yes, I know, Hawaiian royals, Egyptian royals, Abraham married his sister Sarah, and there is one case of a European royal who married his sister and has descendants alive today.

The Hapsburg monarchs in particular encouraged uncle niece marriages to disastrous effect. They killed off their own line, and sent the world to war.

Edgar Allan Poe, Albert Einstein, Franklin Delano Roosevelt, and Jerry Lee Lewis are all famous first cousin marriages in America.

Some biologists claim that the majority of "marriages" in the lifespan of the species were first cousin marriages. Some cultures only permitted marriages of cross cousins which is cousins from the parent's opposite-sexed sibling. That prevents the danger of accidently marrying your own half sibling if your father was fooling around with his sister in law.

But in the 21st century, it seems like an unnecessary risk to very helpless small children.

Still no guesses on the poll.

Quote: pacomartin

Some biologists claim that the majority of "marriages" in the lifespan of the species were first cousin marriages.

That, I don't doubt. For millenia people were extremely clannish and were distrustful of strangers. It makes sense to keep it in the family from the point of view of ignorance. I knew a woman who claimed she had a 3 year affair with her first cousin when she was 19, and he was the love of her life. But she was an idiot. Hey, wait a minute....

Quote: EvenBob

It makes sense to keep it in the family ....

Again, you reminded me of something, Bob -- the old quip, "Vice is nice, but incest is best, so long as you keep it in the family."

Frank, I have no idea how to even start the math analysis.

Quote: Doc

Frank, I have no idea how to even start the math analysis.

It's a sum (possibly infinite) involving powers of 1/2 since each person gets 1/2 their genes from one parent.

You can see the possibility of anger on this issue. In 1960 Pakistan and the UK had roughly the same population. Today Pakistan has 3 times the population of the UK. By bringing this marriage custom to Britain via immigration, their children are said to have 1/3 of the victims of genetic disease in the country. Obviously since you can't cure genetic disease like you can an infection, people who suffer from genetic diseases put a huge burden on the health care system. Not to mention the mental anguish of watching children with painful diseases, on top of knowing that their parents essentially engaged in high risk behavior.

The last high ranking member of the British royal family who married his first cousin (one generation removed) was in 1913. A British prince, named Prince Arthur of Connaught, was born a second son so he did not expect to inherit a title higher than Prince. He boosted his position in the royal family by marrying Princess Alexandra, Duchess of Fife . Despite being one generation removed, she was only 8 years younger than he. Their only son, born Prince Alistair, died in Ottawa, Canada at the age of 29 during WWII. He seems to have gotten drunk and fallen out of a window and died of hypothermia during the night. With the death of the mother in 1959, this family left no descendants. I actually got an e-mail from an Egyptian kid who said his grandfather was Prince Alistair's love child by an Egyptian woman (he had been stationed in Egypt just before going to Canada). Alistair had written her and promised to buck the royal family and marry her just before his untimely death. He wanted to know if I could help him prove his grandfather's legacy. I wished him luck.

The last British monarch who married their first cousin, was famously Queen Victoria and Prince Albert in 1840. Coincidentally, she started the best known genetic disease in history, the line of hemophiliacs that killed over a dozen of her descendants. The Tsaravitch (13 year old son of Nicholas) was born with the disease. The machinations of her mother with the monk Rasputin to cure her son played a part of the downfall of the Romanovs. Of course, the son was shot to death along with the rest of his family before he could die from the disease. The genetic disease and the first cousin marriage were coincidental, as hemophilia is not one of the genetic diseases where marriage to a cousin increases the risk of getting the disease.

I voted that it would be equivalent to the union of a uncle and niece. My degree of confidence is not very high, I'd like to think on it some more.

Did you know Albert Einstein married his first cousin? In fact, I think they were closer than first cousins. ¡Que interesante! From Wikipedia,

"She began a relationship with her cousin Albert Einstein at Easter 1912[4] and married him on June 2, 1919.[5] Elsa's and Albert's mothers were sisters, which made Elsa and Albert first cousins, and their fathers were first cousins."

A good question would be what ratio of genes did either one share with the other?

Quote: pacomartin

It's a sum (possibly infinite) involving powers of 1/2 since each person gets 1/2 their genes from one parent.

There was another genetics-related thread around here not long ago, with an attempt to liken the process to lottery/keno/bingo balls. I didn't really follow the details on that one very well either, but I think one of our members claimed to have some expertise in the field and gave what seemed to be the most plausible explanation.

My concern with summing the powers of 1/2 lies in the issue of dominant and recessive characteristics. In my ignorance, I have the impression that for a single gene type, you do indeed have two possible sources (parents) but that the probability is not 50-50 on what you wind up with. Perhaps this relates to that puzzle issue that this forum seems unable to get consensus on: if there are only two possible amounts of money in the sealed envelope, are they each equally likely?

If the probability is not 50-50, then I don't know how summing powers of 1/2 would lead to a valid answer, and I don't know how to relate the answer to an equivalent, specific relationship of parents as in the poll.

Not that I'm questioning it, but is there a simple way to explain why inbreeding causes health problems in their offspring. I think of genetics as each living thing has so many genes. When there is a mating the offspring randomly choose between the mother and father for each one.

So let's say that both a brother and sister receive the same red hair gene from say the mother's side of the family. For the sake of simplicity, let's say hair color is determined by just one gene, if we can. Then they mate (sorry if this bothers anyone). Would their offspring have a 100% chance of getting this red hair gene? I also can't explain to myself why that tends to cause birth defects. Is it possible to explain it in layman's terms?

Again, I'm not questioning it. As a kid, my neighbor used to breed guinea pigs and inbred them all the time. Often the offspring were born with birth defects like extra toes, blindness, or as paraplegics.

Quote: Wizard

Not that I'm questioning it, but is there a simple way to explain why inbreeding causes health problems in their offspring.

Because relatives have a higher chance of carrying the same recessive genes.

Quote: Nareed

Because relatives have a higher chance of carrying the same recessive genes.

That is exactly correct. I might say the more genetic material you have in common, the more likely that both parents carry the same recessive gene that causes a disease. If the genetic material is chosen randomly, it is still possible that both parents could be carriers of the same recessive gene, but it is a lot less likely. In other words, if we had no marriages closer than 4th cousin, genetic disease would not vanish, but it's risk would diminish greatly.
===========

Most deadly genetic traits (phenotypes) that we refer to as "genetic disease" are carried in the recessive gene. For any two people if list their 22 non-sex chromosones, you will often find one dominant and one recessive gene that causes a disease. There are three types of people:
AA has two dominant genes, and is completely clean
Aa is called a "carrier"
aa has two recessive genes and is sick.

Case 1) Both parents have gene types AA. For this particular disease, their children can not be carriers, nor will they get sick.

Case 2) One parent is "AA" and the other parent is "Aa". In this case the child has a 50% chance of being completely clean, or a 50% chance of being a "carrier"

Case 3) If father and mother both gene type Aa and Aa , statistically one fourth of their children will have "AA" , one half will be "Aa", and one fourth will be "aa". The children will be classified as above.

The more the parents of a child have the same genes, the more likely they will be carriers of a genetic disease. Two parents might be chromosone pairs Bb, Dd, Ff, Pp. Since each child stands a 25% of getting each disease, statistically the odds are high that each child will have one or more of the diseases.

The most dangerous kind of incest for the purposes of evaluating genetic disease, would be a male/female twins that had incest and produced a child. As far as 22 non sex genes both parents would have the same pair. If out of the 22 chromosones, they have 13 carriers combinations, the child only has a 1:2^13 chance of not getting one of the thirteen diseases. So two healthy twins are almost certain to produce a sick child.

The next level of danger would be father/daughter or mother/son or brother/sister incest. Now statistically speaking they have 25% of the genes in common. They still have a strong chance of each providing a copy of the same recessive gene and producing a sick child.

The next level would the equivalent uncle/niece , or aunt/nephew, or half-siblings, or double first cousins. All of these have 12.5% of their genes in common. A double first cousin would be when the grandparents are come from only two families. Although there are several combinations possible assume two brothers marry two sisters. Their children then marry. That child will only have four grandparents instead of eight.

The next level of danger is two first cousins marry. But in a culture that encourages first cousin marriage, the possibility of double first cousins is very high.

Also as the wizard surmised, an infinite series of first cousin marriages, with no other relationship, would be mathematically equivalent to an uncle/niece marriage. In reality you don't need an infinite series, because sooner or later you hit the random relationship floor. But if you have both parents, and some of the grandparents, you are pretty close.

While uncle niece marriages were supposedly only considered once (according to Shakespeare) by British royalty (see Richard III), there were none that I know of. However, the Hapsburg kings had many of them during the 17th and 18th century. By the time the last Spanish Hapsburg king was born, he had the genetic equivalent of being born to full brother/sister coupling or equivalently a father/daughter relationship. He had an endless list of disgusting defects, and was unable to reproduce, producing a vacant throne which led to a world wide war in 1700.


Handsome fellow.

Quote: pacomartin

The most dangerous kind of incest for the purposes of evaluating genetic disease, would be a male/female twins that had incest and produced a child. As far as 22 non sex genes both parents would have the same pair.

No. Male/female twins are fraternal, they can't be any other kind. That is to say, they come from two ova and two sperm. They don't share all 22.5 pairs of genes any more than regular siblings would.

Quote: pacomartin

Case 1) Both parents have gene types AA. For this particular disease, their children can not be carriers, nor will they get sick.

Case 2) One parent is "AA" and the other parent is "Aa". In this case the child has a 50% chance of being completely clean, or a 50% chance of being a "carrier"

Case 3) If father and mother both gene type Aa and Aa , statistically one fourth of their children will have "AA" , one half will be "Aa", and one fourth will be "aa". The children will be classified as above.

What about:

case 4) AA and aa
case 5) Aa and aa
case 6) aa and aa

Quote: Paco

The most dangerous kind of incest for the purposes of evaluating genetic disease, would be a male/female twins that had incest and produced a child.

I agree with Nareed's response to this. Fraternal twins are no more alike genetically than any other two full siblings, except identical twins.

Quote: Wizard

What about:

case 4) AA and aa
case 5) Aa and aa
case 6) aa and aa



I agree with Nareed's response to this. Fraternal twins are no more alike genetically than any other two full siblings, except identical twins.

That was kind of stupid of me. You are correct.

Case 4-5 where one parent has a disease is a little different than consanguine marriages.

If you marry someone with a known autosomal genetic disorder, then your child must either be sick or a carrier. That traditionally was the tragedy of Amyotrophic lateral sclerosis, where symptoms don't appear until after age 50. When they appear, you must not only confront the fact that you will die badly, but now your children have a 50% chance of having the disease. Newer research indicates that ALS is not always hereditary. But it is the risk you get from marrying someone with a known genetic disorder, not a risk increased by marrying a close cousin.

I believe case #6 is illegal if you know about it. If two people are known to have the same recessive genetic disorder (assuming it is severe), and their offspring have a nearly 100% chance of getting the disease, then they are not permitted to marry and reproduce.


Why did I ask the question?
One of the reasons was that first cousin marriages are supposed to have only a small percentage increased chance of producing a genetic disease. That is why it is legal in Europe, Canada, Mexico and in many states in the USA. Read the Slate Magazine article which says that the odds are 7% for first cousin marriages.

How do we explain the numbers in the BBC stories? Even allowing for "double first cousin" marriages and a family tree of first cousin marriages it is difficult to see how the BBC numbers can be accurate. Here is a British video show called Dispatches on the subject.

Quote: BBC

But the statistics for recessive genetic illness in cousin marriages make sobering reading.
British Pakistanis are 13 times more likely to have children with genetic disorders than the general population - they account for just over 3% of all births but have just under a third of all British children with such illnesses.

A multiplier of 13 seems huge to me. If first cousin marriages only double the chance of genetic disorder, then how do you get to 13? Even if you have multi-generational cousin marriages should only double. How many "double cousin" marriages are involved?

What about the USA? Right now much of our immigration comes from Catholic countries which traditionally are extremely cautious about close marriages. At one point the Catholic church required you be 3rd cousin or higher.

Immigration from new parts of the world will surely increase in upcoming years. Should we have nationwide laws regarding first cousin marriage? It would seem to be better off passing the laws now, before we have a million such marriages.UK has a government department called the "forced marriage unit". Although forced marriage is illegal in the USA, I don't think their are divisions of the state department solely dedicated to this issue.

Quote: pacomartin

As far as 22 non sex genes both parents would have the same pair. If out of the 22 chromosones, they have 13 carriers combinations, the child only has a 1:2^13 chance of not getting one of the thirteen diseases. So two healthy twins are almost certain to produce a sick child.

Thanks. I'm learning a lot from this area of science I'm weak in. Mostly for my own benefit, here is a good web page that explains it: http://anthro.palomar.edu/mendel/mendel_2.htm.

There are a number of questions I could ask. The first ones that come to mind are:

1. Is 13 a number you pulled out of thin air, or are there 13 common genetic disorders you are referring to?
2. With a common genetic disorder, like cystic fibrosis, what percentage of the population are AA, Aa, and aa?
3. Is there a convenient blood test for common genetic disorders? I could see that day when people post their genetic disposition on sites like eHarmony to ensure healthy offspring. I, for one, think that would be a good thing. Too bad Hitler gave eugenics a bad name.

Quote: pacomartin

How do we explain the numbers in the BBC stories? Even allowing for "double first cousin" marriages and a family tree of first cousin marriages it is difficult to see how the BBC numbers can be accurate.

It is not outside of the realm of possibility that, due to generations of closely related intermarriages, a large portion of the current Pakistani population in the UK are already carrying problematic recessive genes (a factor of 13 times the general population is not out of bounds). A key figure is the incidence of genetic malformation in the general population in Pakistan. Perhaps folks in Pakistan just have a higher incidence of genetic problems due to environmental causes, like chemical and/or radiation exposure. It is certain that many premature deaths in Pakistan are not attributed to genetic problems, as most children live in squallor, and have never been in a facility that tests for genetic problems.

Quote: Wizard

Thanks. I'm learning a lot from this area of science I'm weak in. Mostly for my own benefit, here is a good web page that explains it: http://anthro.palomar.edu/mendel/mendel_2.htm.

There are a number of questions I could ask. The first ones that come to mind are:

1. Is 13 a number you pulled out of thin air, or are there 13 common genetic disorders you are referring to?
2. With a common genetic disorder, like cystic fibrosis, what percentage of the population are AA, Aa, and aa?
3. Is there a convenient blood test for common genetic disorders? I could see that day when people post their genetic disposition on sites like eHarmony to ensure healthy offspring. I, for one, think that would be a good thing. Too bad Hitler gave eugenics a bad name.

1. The number 13 the first time I used was just a number I pulled out of thin air. The second time I used it was in reference to a very often repeated fact that Pakistani - British have 13 times the rate of genetic disease than the population at large.
2. I don't know. I suspect every time you ask a question like that, you will find that there are several related diseases called cystic fibrosis. It seems like every time I look up any disease, I find all kinds of subcategories.
3. Genetic testing is very common. One of the issues with the cousin marriages is that some people would like the parents to get testing to see which diseases they are carriers of before they marry. The three counter-arguments are common: (1)Why test just cousins couples? Why not have mandatory testing for everyone? (2) Even if you are both carriers there is still only a 1 in 4 chance of the child getting a disease. Should you not marry based on a percentage possibility? Isn't life a risk? (3) Should we prevent other high risk people (like older couples) from marrying and possibly having children?

While many people do object to eugenics with visions of obsession with a master race, it is hard to understand how genetic testing can be a problem.

The US state of Maine allows first-cousin marriage if the couple agrees to have genetic counseling (which I assume either requires or strongly recommends genetic testing), while North Carolina allows it so long as the applicants for marriage are not rare double first cousins, meaning cousins through both parental lines

In general humanity may pay a huge price for protecting reproductive rights. Many people get hysterical if you question any reproductive rights, if it is genetic testing, mandatory sterilization, or even mandatory education. But the lag time for China from introducing a one child per couple birth policy to zero population growth was 50 years. During that time China went from about 1 billion to it's estimated peak under 1.5 billion. Look at that video that I posted showing a Pakistani British family trying to take care of three severely disabled children with genetic disease. All three are blind, with numerous other psychological, physical, and intellectual problems.

Without any data, there could be many cases of "double first cousins" on top of generations of "first cousin" marriage. Plus given that sex abuse is prevalent in all cultures, there could be children of uncle niece relationships in the 19th century that are still affecting the gene pool.

The Pope's stand on birth control doesn't help either. Infallible my Catholic ass.

Quote: buzzpaff

The Pope's stand on birth control doesn't help either. Infallible my Catholic ass.

This is getting off topic, and if this tangent gets far, I'll split it off, but I think that Catholics believe that the Pope is not infallible, and is capable of sinning. I think the Pope is said to be infallible only when declaring a doctrine of the church. Birth control I think is more of a position, and doesn't fall under the umbrella of infallibility.

So his position is not infallible. But as a shepherd for his flock, it is asinine. And harms so many innocent children!

The 13x the genetic defect figure is, well, pretty darn idiotic in the original report. Who the heck cares about only the marginal percentage change in an issue like this. It's no more useful than only knowing the absolute change. We need to know BOTH.

Say the 13x figure is correct, as I have no reason to believe otherwise. However the total numbers could be 10 annual genetic defects to native Englishmen and 5 to immigrants. If the immigrants make up 3% of the population the 13x rate would work. I wouldn't however be too up in arms about launching a massive campaign to prevent 5 instances of birth defects. Likewise if the percentage change was low, like 10% higher from immigrants, but immigrants made up half the population and the baseline rate of defects was very high the 10% change could stil be 100s of thousands of new cases.

My guess as to why it's considered "safe" to allow first cousin marriages is because it takes the risk from "almost zero" to "pretty darn low." That doesn't make a very good news story though so instead they combine a Scary Statistic with a Scary Anecdote and here we are...

EDIT:

Quote: buzzpaff

So his position is not infallible. But as a shepherd for his flock, it is asinine. And harms so many innocent children!

One-line objection: seen vs unseen. The policy also means many more people are born, and it's possible that pool will contain a lot more Einsteins than Hitlers or (considering the site) Shacklefords than Singers.

Try selling that to an impovershed starving kid !

Try selling that to an impovershed starving kid !

Quote: sunrise089

The 13x the genetic defect figure is, well, pretty darn idiotic in the original report. Who the heck cares about only the marginal percentage change in an issue like this. It's no more useful than only knowing the absolute change. We need to know BOTH.

Let's look at some specific numbers. For cycstic fibrosis (CF), the carrier rate in Europe is 1 in 25. In Ireland it is highest at 1 in 19, but let's stick with Europe at large.

So the probability of a European mating resulting in a child with CF would be (1/25)*(1/25)*(1/2)*(1/2) = 1 in 2,500. The population of Europe is about 850 million. So if everybody was tested to avoid two-carrier matings then there would be 340,000 less cases of CF, assuming zero population growth.

I'm not sure what the cost of a test is, but to make a wild guess, let's say $100. So if everyone in Europe were tested it would cost 85 billion. If the cost to care for one CF patient was $250,000 then society would break even, at least financially, to test everyone. However, there is also a benefit to the children themselves being born without it. Maybe my $100 per test estimate is low, but it seems to me that we should take a closer look at genetic testing, at least on a voluntary basis.

Homework problem: Assuming a CF carrier rate of 1 in 25. What would be the probability of the product of first cousins mating having CF? Assume that nobody positive for CF will mate. Note, I did this problem myself, and it was harder and more tedious than I thought. I hope at least one person will give this a try. Miplet?

Hemophilia is a sex linked disease (link to X chromosone). Since it is rare for a man to have the recessive gene, normally half the female children become carriers, while the boys have a 50% probability of getting the disease. In the case of Queen Victoria she carred the recessive gene.

Essentially the sons of Victoria and Albert beat the odds, because out of four sons, only 1 was sick and only lived to age 20. But out of 4 daughters who had children, 2 were carriers (one daughter never had children, so they may have actually done worse than 50%).

The third child, and second daughter, Princess Alice would die of diptheria at the age of 35, but she had five daughters and 2 sons. True to the percentages 2 of the 5 daughters would be carriers, and 1 of the 2 sons would die from the disease (at age 2).

The 2 carriers were Irene who had 3 sons (2 of whom died from the disease, and Alexandra who married the Tsar of Russia. Alexandra's only son had the disease, and nobody knows the status of her 4 daughters since all were shot to death in 1918.

In total, 5 female descendants were known to be carriers, and 10 males certainly died from the disease. Only one male sufferer of the disease lived long enough to have a daughter and pass it on to his grandchildren. Since several people died prematurely (either naturally or murdered) and some women never produced children, the extent of the disease may have been much worse.

In about 30% of cases there is no family history of the disorder and the condition is speculated to be the result of spontaneous mutation. The most common guess is that Victoria is that she or her father had the spontaneous mutation.


The most famous sufferer was Alexei Nikolaevich, Tsarevich of Russia who was shot to death at 13.

Quote: sunrise089

The 13x the genetic defect figure is, well, pretty darn idiotic in the original report. Who the heck cares about only the marginal percentage change in an issue like this. It's no more useful than only knowing the absolute change. We need to know BOTH.

In Britain it is roughly 15K severe genetic diseased children born per per year, of which roughly 5K are from Pakistani families. The population of the UK is 62.7 million, and they have 771K births, and 585K deaths this year. So it is 1 child in 50 born with a severe genetic disease.

We know British Pakistanis constitute 1.5 per cent of the population, yet a third of all children born in this country with rare recessive genetic diseases come from this community.

So if Health Care costs are roughly £1600 per year per capita in the United Kingdom, then these 5000 genetically disabled children of Pakistani immigrants cost £75,000 per year apiece. Also the lions share will be concentrated in certain communities like Bradford where one quarter of the community is of British Asian descent.


Mea Culpa, I just realized part of the reason why the multiplier is so high. Pakistani-British immigrant mothers have 5 children apiece on average. So their percent of the children of the children is much higher than the Pakistani percent of the population. I am not sure where to find that specific number, but the Pakistani mothers must be having 50K to 70K children per year.

Quote: Daily Mail

The greatest taboo: One woman lifts the lid on on the tragic genetic consequences of when first cousins marry By TAZEEN AHMAD, 23rd August 2010

On average, a children’s hospital will see 20 to 30 recessive gene disorders a decade, but one hospital in Bradford has seen 165, while British Pakistani children are three times more likely to have learning difficulties, with care costing about £75,000 a year per child.

Bradford is a portion of Birmingham with a very high level of Pakistani immigration.

Quote: Wizard

So the probability of a European mating resulting in a child with CF would be (1/25)*(1/25)*(1/2)*(1/2) = 1 in 2,500. The population of Europe is about 850 million. So if everybody was tested to avoid two-carrier matings then there would be 340,000 less cases of CF, assuming zero population growth.

I will try your homework problem, but I have some actual vital statistics for you. Given a population of 736.5K for Europe (possibly you included Turkey?) there will be 7.6 million births, and 8.5 million deaths this year, and 1 million legal immigrants.

Clarification on homework problem: Do the first cousins marriages have children at the same rate as the general population?

Quote: pacomartin

I will try your homework problem, but I have some actual vital statistics for you. Given a population of 736.5K for Europe (possibly you included Turkey?) there will be 7.6 million births, and 8.5 million deaths thiss. year, and 1 million legal immigrant

Clarification on homework problem: Do the first cousins marriages have children at the same rate as the general population?

I don't remember where I picked up that number. For the homework problem, the fertility rate should not matter. Just look at a specific mating of a first cousin pair. All you should need to know is that other than the first cousins, everyone marries random people, except those positive with CF choose to not mate.

Quote: Nareed

No. Male/female twins are fraternal, they can't be any other kind. That is to say, they come from two ova and two sperm. They don't share all 22.5 pairs of genes any more than regular siblings would.

Although very rare it is possible for what would still be called 'identical twins' to be of different sexes. The sex chromosomes can have a problem when splitting and not split properly producing twins of opposite sexes that have the remainder of their genes substantially the same.

I guess my last homework problem was a bit too hard. Let me try this one, which I plan to make an "ask the wizard" question out of. I'd feel more comfortable if somebody else came up with the same answer I did. That said, here is the question:

The carrier rate of Cystic Fibrosis of those of European descent is 1 in 25 people. Assuming that nobody positive for Cystic Fibrosis will reproduce, and no incest, and a constant period of time between generations, how many generations will it take for this rate to be reduced in half, or to 1 in 50 people?

I think part of the problem is that mutations can appear spontaneously. This means an individual can be afflicted, or a carrier, without a genetic heritage.

Quote: Wizard

Homework problem: Assuming a CF carrier rate of 1 in 25. What would be the probability of the product of first cousins mating having CF? Assume that nobody positive for CF will mate. Note, I did this problem myself, and it was harder and more tedious than I thought. I hope at least one person will give this a try. Miplet?

Assuming the CF carrier rate includes the current generation, and CF postive individuals do not mate, then does it matter if two of the couple's four parents are siblings? The probability of two carriers mating and producing a CF positive offspring should still be (1/25)*(1/25)*(1/2)*(1/2) = 1 in 2,500

Those who killed all the men and raped all the women prospered. Then it was those who guarded the women and mated them with first cousins who prospered. Even now incest taboos are often breaking down because sex is so often recreational and is so rarely procreational these days. In England and Wales and in some areas of the USA, if a wife died or became incapable of meeting her husband's needs it was common for a husband to turn to the oldest daughter.

Certain sub-populations do present a genetic burden to the public tax coffers.

Quote: Wizard

I guess my last homework problem was a bit too hard. Let me try this one, which I plan to make an "ask the wizard" question out of. I'd feel more comfortable if somebody else came up with the same answer I did. That said, here is the question:

The carrier rate of Cystic Fibrosis of those of European descent is 1 in 25 people. Assuming that nobody positive for Cystic Fibrosis will reproduce, and no incest, and a constant period of time between generations, how many generations will it take for this rate to be reduced in half, or to 1 in 50 people?

I will make a try at the answer so maybe you can tell me where I go wrong.

Forgetting about how they got the recessive gene in the first place, and ignoring mutations. All marriages are random, but end up at 4th cousin or more distant.

The mythical land has 250,000 people with 125,000 of each sex and 5,000 of each sex have the recessive gene. They form 125,000 couples, out of which only 200 (125,000/25^2) have the recessive gene in both parents.

The 200 couples have 400 children. The clean children number 100, 200 have the recessive gene, and 100 are sick and are not permitted to reproduce.

Out of the other 124,800 couples 9,600 couples (10,00-400) have one parent with the recessive gene. Out of these marriages which produce 19,200 children, then 2400 have the recessive gene and 16,800 clean.

The total of "clean" couples are 124,800-9,600=115,200 which produce 230,400 children.

So the clean children are 230,400 + 16,800 +100=247,300 . The ones with recessive gene are 2400+200=2600 out of 249,900 next generation who are allowed to reproduce.

So already the rate is 2,600 carriers out of 249,900 for the next generation. Which is better than 1 in 100 (well below your target level in one generation).

Quote: FleaStiff

Those who killed all the men and raped all the women prospered. Then it was those who guarded the women and mated them with first cousins who prospered. Even now incest taboos are often breaking down because sex is so often recreational and is so rarely procreational these days. In England and Wales and in some areas of the USA, if a wife died or became incapable of meeting her husband's needs it was common for a husband to turn to the oldest daughter.

Certain sub-populations do present a genetic burden to the public tax coffers.

I am not sure if you have any basis for your first statement or if it is just a rant.

The second one is a problem. I am perfectly willing to support national law in the USA that prohibits first cousin marriage without mandatory sterilization, or makes it a requirement for immigration. I would grandfather the existing population.

I don't see a problem with passing laws to prevent a problem that may occur in the future. Plus there is scientific justification for the law.

Our heaviest states for foreign immigration do not have any laws.
District of Columbia: First cousins, yes.
Florida: First cousins, yes.
California: First cousins, yes.
New Jersey: First cousins, yes.
New Mexico: First cousins, yes.
New York: First cousins, yes.

Some states have some sort of restriction
Montana: Half cousins, yes.
Nebraska: Half cousins, yes.
Nevada: Half cousins, yes.
North Carolina: First cousins, yes. Double first cousins are not allowed to get married.
Arizona: First cousins, yes, only if they are over a certain age or cannot bear children. Half cousins, yes.
Minnesota: No, unless aboriginal culture of the couple permits cousin marriages.
Utah: First cousins, yes, only if they are over a certain age or cannot bear children.


Right now, only a about 1/3 prohibit all first cousin marriages
Mississippi: Adopted cousins, yes.
Arkansas: No
Delaware: No
Idaho: No
Iowa: No
Kentucky: No
Louisiana: No
Michigan: No
Missouri: No
New Hampshire: No
North Dakota: No
Ohio: No
Pennsylvania: No
South Dakota: No
Texas: No
Washington: No
Wyoming: No

Quote: Ayecarumba

I think part of the problem is that mutations can appear spontaneously. This means an individual can be afflicted, or a carrier, without a genetic heritage.

Let's ignore that.

Quote: Ayecarumba

Assuming the CF carrier rate includes the current generation, and CF postive individuals do not mate, then does it matter if two of the couple's four parents are siblings? The probability of two carriers mating and producing a CF positive offspring should still be (1/25)*(1/25)*(1/2)*(1/2) = 1 in 2,500

Agreed. That is one step out of many toward the right answer. Remember, I asked about the carrier rate, not the positive rate.

Quote: paco

Out of the other 124,800 couples 9,600 couples (10,00-400) have one parent with the recessive gene. Out of these marriages which produce 19,200 children, then 2400 have the recessive gene and 16,800 clean.

I disagree. If a carrier and somebody clean mate, then the offspring will have a 50% chance of being a carrier. So out of 19,200 children 9,600 would be carriers.

Quote: Wizard

I guess my last homework problem was a bit too hard. Let me try this one, which I plan to make an "ask the wizard" question out of. I'd feel more comfortable if somebody else came up with the same answer I did. That said, here is the question:

The carrier rate of Cystic Fibrosis of those of European descent is 1 in 25 people. Assuming that nobody positive for Cystic Fibrosis will reproduce, and no incest, and a constant period of time between generations, how many generations will it take for this rate to be reduced in half, or to 1 in 50 people?

I get 103

Quote: miplet

I get 103

Whenever I disagree with miplet I have to pause and reflect that I may be wrong. To help us find our point of departure, can you give me the carrier rate for the first and second generations?

0.0396
0.039223492518256
0.038853965462115
and of course I have to head out for work now. Back home around 1am.

Quote: miplet

0.0396

I don't agree with even the first generation. Let's continue this up by PM.

Calculations assume all offspring marry (including CF positive) and reproduce (except CF positive)?

Quote: Ayecarumba

Calculations assume all offspring marry (including CF positive) and reproduce (except CF positive)?

I would say that shouldn't matter. I will say that carriers and negatives reproduce at the same rate.

The answer isn't 42?

Seriously, math can only take you so far.

The thinking is that a recessive trait will be rarer every generation until it's gone, replaced by dominant traits or by a more common recessive trait. Unless other factors are involved.

Take the gene for sickle-cell anemia, which is recessive. Why is it still here, it it causes a serious and debilitating disease? Because the people who are carriers but not affected by sickle-cell have some resistance to the malarial parasite absent in non-carriers. In a region rife with malaria, this recessive trait gives carriers a better chance to live long enoug to reproduce and, imoprtant in our species, raise children. Thus their "bad" recessive gene gets passed along.

As it happens the sickle-cell gene is prevalent in areas rife with malaria. alas it's also prevalent among people descended from those who lived in those areas. in this case ti affects black people.

Somethign similar happnes with the gene for Tay Sachs syndrome. carriers have some resistance to tuberculosis. that came in very ahdny among Ashkenazi jews in the crowded cities of Estern Europe, where this recessive gene is abundant.

But there can be other effects. Blue eyes are a recessive trait. But if enough people find them attractive in the opposite sex, and seek to have sex with blue-eyed men or women, the genes for blue eues will stay around a while.

There are other things like the Founder Effect, but that's another story.

Quote: miplet

0.0396
0.039223492518256
0.038853965462115

I showed my math to Miplet who said he made an error in his figures above, and agree with mine. As a hint, the first generation from now should have a carrier rate of 0.039215686.

Quote: Nareed

Blue eyes are a recessive trait. But if enough people find them attractive in the opposite sex, and seek to have sex with blue-eyed men or women, the genes for blue eues will stay around a while.

I would call that a byproduct of the theory of evolution. Call it survival of the most attractive.

Quote: Wizard

I would call that a byproduct of the theory of evolution. Call it survival of the most attractive.

Actually it's called sexual selection.

There are other kinds of selections that can change a species or a part of a species over time. The most common goes back to pre-history, where our ancestors cultivated rare varieties of grains that yielded more food. The naturally ocurring corn plants, for instance, have only a few kernels. Dogs are essentially a sub-species of wolf selectively bred to suit our needs.

Quote: Nareed

Actually it's called sexual selection.

What else could explain such things as the feathers of a male peacock?

Reminds of one of my favorite Far Side cartoons. There are two female peacocks (peahens) at a bar. A male peacock is in full display nearby, trying to get their attention, as one of the peahens glances his way. The other peahen says to her, "Don't encourage him."

Quote: Wizard

What else could explain such things as the feathers of a male peacock?

I read somewhere that peacocks with the brightest feathers are more resistant to parasites...

On the other hand, a human prefference for certain eye color could eihter keep a gene in the pool, or drive up the sales of tinted contacts :P

Quote: Nareed

I read somewhere that peacocks with the brightest feathers are more resistant to parasites...

I read somewhere that male birds in general show off their feathers at least partially to prove they don't have parasites in them.