ECOLOGY O.Population genetics new.pdf

O. Population Genetics 种群遗传学 O1.Genetic ? gene(基因)：带有可产生特定蛋白的遗传密码 的DNA片段 ? 基因库(gene pool)：种群中存在的所有基因 组和等位基因。 ? 基因是成对结构，由两个等位基因构成，每一 等位基因来自一条同源染色体。这些等位基因 可以相同或不同。 O1O1 GGENETICENETIC VARIATIONVARIATION 遗传的变异遗传的变异 Key Notes 要点 Genes and alleles Genes are pieces of DNA which contain the genetic code 基因和等位基因 necessary to produce a specific protein. A gene can have many alleles and individuals can have a homozygous or heterozygous genotype. The phenotype expressed depends on whether alleles are dominant, recessive or codominant. The total set of genes and alleles present in a population is known as the gene pool. 基因是带有可产生特定蛋白的遗传密码的DNA片段。一 个基因可有许多等位基因，而个体可有纯合或杂合的基 因型。表达的表现型取决于等位基因是显性的、隐性的 还是共显性的。种群中存在的所有基因组和等位基因叫 做基因库。 ? Polymorphism （多型）：在种群中许多等位 基因的存在导致一种群中一种以上的表现型。 Polymorphism The term polymorphism refers to the presence of alleles in a 多型 population. A population or species may be polymorphic for color, as in snails, or for some biochemical function, as in plant toxicity. Some polymorphisms are maintained by natural selection, but others appear to result from the effect of many genes controlling the polymorphic character. 多型指的是种群中等位基因的存在。一个种群或物种可 能颜色是多型的，如蜗牛，或者一些生化特性是多型 的，如植物的毒性。一些多型可能是由自然选择保持下 来的，但其他是由于许多基因控制多型性状的结果。 ? Seashore molluscs such as winkles,dog whelks and clams coexist in different shell color forms.Some polymorphisms appear to be maintained by natural selection;in the land snail,Cepaea nemoralis,shell color and banding is at least partly related to camouflage and the temperature regime of the l