APY248 Exam 3 Lecture Notes

APY248 Exam 3 Lecture Notes - March22,2010 I A...

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March 22, 2010 I. Inbreeding- involves mating between relatives who are biologically related to each other A. Consanguinity = with blood II. Cultural mating A. Societies have their own mating rituals B. Some have uncle and niece mate C. Catholic church is against marriages between relatives C.1. Occurred in 11 th  century C.2. Marriages could occur with an application- papel dispensation C.3. Provided a great deal of levels of inbreeding over time III. Biological effects A. Offspring of consanguineous parents B. Genes may be identical by descent from a common ancestor B.1. May have been coded off the same DNA strand C. Inbreeding coefficient (F) measure of probability of identity by descent  C.1. Handout on UBlearns C.1.i. Inbreeding coefficient is 1/8  C.2. Draw a pedigree including only individuals who are from the common ancestor C.3. Find all the different paths from the offspring to the common ancestor, and back C.4. Count individuals on the path C.4.i. Start with I, and go around the circle to get back to I = 3 people C.4.i.a) ½ ^nth power C.5. With 2 common ancestors, grandma and grandpa, 2 separate paths C.5.i. ( ½ )^3 + (1/2)^3  C.5.ii. F =  ¼   C.6. Overall effect of inbreeding increases the probability of homozygous recessives including those  which are harmful, deleterious, risk increases as the inbreeding coefficient increases. As it goes up,  deleterious recessive disorder goes up proportionally.  C.7. Each of us carries 4-7 lethal equivalents- genes, homozygous for, we wouldn’t survive. But people  are mostly healthy because they lethal equivalents we carry are rare as a whole, when we marry  somebody they’re not likely to have the same lethal equivalent. If you’re making babies with somebody  closely related to you, you’re increasing the risk of finding matches for your lethal alleles and  transmitting them to your offspring. C.8. Usually happens in small communities where there is nobody else to marry and it’s just going to  happen. C.9. 64 ancestors for each individual, 2 individuals must share SOME alleles. C.10.  Genetic isolation leads to some unavoidable inbreeding C.11.   Inbreeding in the case of recessive genes, a disproportionate number of pedigrees who have  affected individuals are the result of consanguinity C.12.  Caucasian population, fewer than 1% are between cousins  C.13.  12-18% between albinos, their parents were related to each other C.14.  Genetic isolates are specific recessive disorders C.15.
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