①a gene frequency = total number of A genes/(total number of A genes+total number of A genes) =(2n 1+n2)/2N or n 1/N+n2/2N.
②AA genotype frequency = number of AA genotype individuals/total diploid population = n1/n.
⑵ The calculation relationship between gene frequency and genotype frequency is deduced from the above ① and ②: A gene frequency = n 1/n+ 1/2 N2/n = AA genotype frequency+1/2 AA genotype.
Types of gene frequency calculation and its formula derivation
The second type: calculation in natural state.
For the population living in nature, ideal conditions can't exist at the same time, and the gene frequency of the population can't be balanced, but it is constantly changing and developing. This unbalanced population often uses the data obtained from sampling survey to calculate its gene frequency, which can be divided into two types according to the location of genes.
2. Calculation of1autosomal gene frequency
According to the definition, the frequency of a gene = the number of a gene/the total number of alleles of this gene × 100%. If a diploid organism has a pair of alleles A and A at a certain locus on its autosome, their gene frequencies are P and Q, respectively, and three genotypes of aa, aa and Aa can be formed. The genotype frequencies are D, H and R, respectively. The total number of individuals is n, the number of Aa individuals is n 1, the number of AA individuals is n2, and the number of AA individuals is n3 and N 1+. So:
Genotype frequency AA =D=n 1/N, n1= nd;
Genotype Aa =H=n2/N, n2=NH frequency;
Genotype frequency aa =R=n3/N, n3 = NR.
The frequency of gene a is p (a) = (2n1+N2)/2n = (2nd+NH)/2n = d+1/2h = p.
The frequency of gene a is p (a) = (2n3+N2)/2n = (2nr+NH)/2n = r+1/2h = q.
Because p+q= 1, d+1/2h+r+1/2h = d+r+h =1.
As can be seen from the above inference,
① Basic calculation formula of autosomal gene frequency:
The frequency of gene A =(2× the number of homozygotes of the gene+1× the number of heterozygotes) /2× the total number of individuals in the population survey.
② Derivation and calculation formula of autosomal gene frequency:
Frequency of gene = homozygous frequency of gene+1/2 heterozygous frequency.
Extended data
Gene frequency refers to the ratio of a gene to all alleles in the population gene pool. The frequency of specific genes in the population can be estimated by genotype frequency. For example, the well-known human MN blood group is determined by a pair of dominant alleles M and N, resulting in three genotypes: M/M, M/N and N/N, and the corresponding phenotypes are M, MN and N, with the proportions of 1/4M, 1/2MN and 1/4N respectively.
This principle can be extended to general group mating, for example, the relative frequency can be obtained by dividing the specific sample number of MN phenotype (genotype) in the group by the total number observed.
References:
Baidu encyclopedia of gene frequency