文档介绍：06疾病的多基因遗传Monogenic Inheritance
Multifactorial inheritance is responsible for the greatest number of individuals that will need special care or hospitalization because of ic diseases.
Up to 10% of newborn children will express a multifactorial disease at some time in their life. Atopic reactions, diabetes, cancer, spina bifida/anencephaly, pyloric stenosis, cleft lip, cleft palate, congenital hip dysplasia, club foot, and a host of other diseases all result from multifactorial inheritance.
Some of these diseases occur more frequently in males. Others occur more frequently in females. Environmental factors as well as ic factors are involved.
1. REGRESSION TO THE MEAN
Multifactorial inheritance was first studied by Galton, a close relative of Darwin and a contemporary of Mendel. Galton established the principle of what he termed "regression to mediocrity."
Galton studied the inheritance of continuous characters, height in humans, intelligence in humans, etc.
Galton noticed that extremely tall fathers tended to have sons shorter than themselves, and extremely short fathers tended to have sons taller than themselves. "Tallness" or "shortness" didn't breed true like they did in Mendel's pea experiments. The offspring seemed to regress to the median, or "mediocrity."
paring height differences between men and women, women are, on average, 3 inches shorter. A woman with a certain number of "tall" genes will be, on average, 3 inches shorter than a man with the same number. When that difference is taken into account, there is no selective bias in matings for tallness in human populations.
It is true than men tend to marry women who are shorter than themselves, but that is a phenotypic difference, not a genotypic difference. Since the wives of taller than average men tend to represent the general population of women, they will not have, on the average, as many "tall" genes to pass on to their offspring as their husbands.