Many species are made up of local populations whose members tend to breed within the group. So, recessive genes do not tend to be lost from a population no matter how small their representation. But substituting in the middle term ( 2pq) of the expansion gives the percentage of heterozygous hamsters. Because B is completely dominant over b, we cannot distinguish the Bb hamsters from the BB ones by their phenotype. ![]() Since p + q = 1, p = 0.8 and allele B makes up 80% of the gene pool. Q 2 = 0.04, so q = 0.2, the frequency of the b allele in the gene pool. In fact, because we chose to make B fully dominant, the only way that the frequency of B and b in the gene pool could be known is by determining the frequency of the recessive phenotype (gray) and computing from it the value of q. The algebraic method enables us to work backward as well as forward. In our example, p = 0.8, q = 0.2, and thus \.\(2pq\) = the fraction of heterozygotes.\(q^2\) = the fraction homozygous for \(q\).\(p^2\) = the fraction of the population homozygous for \(p\).Let \(p\) represent the frequency of one gene in the pool and \(q\) the frequency of its single allele.The total number of genes in a population is its gene pool. Now let us look at an algebraic analysis of the same problem using the expansion of the binomial ( p+ q) 2. The heterozygous hamsters ensure that each generation will contain 4% gray hamsters. The proportion of allele b in the population has remained the same. So we have duplicated the initial situation exactly. All the gametes of the gray ( bb) hamsters (4%) will contain b but one-half of the gametes of the heterozygous hamsters will as well.5*0.32) of the pool of gametes formed by this generation with contain B. All the gametes formed by BB hamsters will contain allele B as will one-half the gametes formed by heterozygous ( Bb) hamsters.Will gray coated hamsters eventually disappear? No. So 96% of this generation will have black coats only 4% gray coats. Random union of these gametes (right table) will produce a generation: Let us take as a hypothetical case, a population of hamsters in which 80% of all the gametes in the population carry a dominant allele for black coat ( B) and 20% carry the recessive allele for gray coat ( b). However, the frequency of two alleles in an entire population of organisms is unlikely to be exactly the same. Results of random union of the gametes produced by an entire population with a gene pool containing 80% B and 20% b. As a result of meiosis, half the gametes produced by each parent with carry allele B the other half allele b. (Left table) Results of random union of the two gametes produced by two individuals, each heterozygous for a given trait. It occurs because meiosis separates the two alleles of each heterozygous parent so that 50% of the gametes will carry one allele and 50% the other and when the gametes are brought together at random, each B (or b)-carrying egg will have a 1 in 2 probability of being fertilized by a sperm carrying B (or b). ![]() ![]() This is what Mendel found when he crossed monohybrids.
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