Denic Srdjan, Frampton Chris, Nagelkerke Nicolas, Nicholls M Gary
Faculty of Medicine and Health Sciences, UAE University, Al Ain, Abu Dhabi, United Arab Emirates.
Ann Hum Biol. 2007 Nov-Dec;34(6):620-31. doi: 10.1080/03014460701615993.
In populations with alpha(+)-thalassemia gene deletion, the practice of consanguineous marriages is common.
The study explored the impact of consanguinity (inbreeding) on the selection of alpha(+)-thalassemia genotypes in a computer model.
In a population under selection pressure from malaria, a single protective mutation (-alpha/alphaalpha genotype) was introduced among normal genotypes (alphaalpha/alphaalpha), and mating allowed to proceed. Heterozygote (-alpha/alphaalpha) and homozygote (-alpha/-alpha) children were 1.5 and 2.5 times more likely to survive malaria than those with normal genotypes. Using different coefficients of inbreeding (F, range 0-0.12), we examined the effect of population size, and the mean number of generations required for the homozygote frequency to reach 0.5.
On average, consanguineous populations were larger than randomly mating populations and the size was directly proportional to F. In more inbred populations,-alpha/-alpha homozygotes reached a frequency of 0.5 faster than in less inbred populations. As the frequency of the alpha(+)-thalassemia allele in a population increases, however, the positive effect of inbreeding on the population growth decreases.
Under selection pressure from malaria, consanguinity may increase the speed of selection of-alpha/-alpha homozygotes and provide an advantage regarding population growth over non-consanguineous populations.
在携带α（+）-地中海贫血基因缺失的人群中，近亲结婚的现象很常见。
本研究在计算机模型中探讨近亲结婚（近亲繁殖）对α（+）-地中海贫血基因型选择的影响。
在一个受到疟疾选择压力的人群中，在正常基因型（αα/αα）中引入一个单一的保护性突变（-α/αα基因型），并允许交配进行。杂合子（-α/αα）和纯合子（-α/-α）儿童患疟疾存活的可能性分别是正常基因型儿童的1.5倍和2.5倍。使用不同的近亲繁殖系数（F，范围为0 - 0.12），我们研究了种群大小的影响，以及纯合子频率达到0.5所需的平均世代数。
平均而言，近亲繁殖的种群比随机交配的种群更大，且种群大小与F成正比。在近亲繁殖程度更高的种群中，-α/-α纯合子达到0.5频率的速度比近亲繁殖程度较低的种群更快。然而，随着种群中α（+）-地中海贫血等位基因频率的增加，近亲繁殖对种群增长的积极影响会降低。
在疟疾的选择压力下，近亲结婚可能会加快-α/-α纯合子的选择速度，并在种群增长方面比非近亲结婚的种群具有优势。
