Inheritance 0.0 / 5 ? BiologyDNA, genetics and evolutionA2/A-levelAQA Created by: Polaris03Created on: 09-11-20 21:33 Definitions Independent assortment - genes separate independently of each other when gametes are made. Except for linked genes - v close together so more likely to be inherited as a pair, less likely to be separated during recombination. Hemizygosity - no role of dominance and recessiveness (e.g. sex-linked genes). Epistasis - one gene masks another, alleles being masked are hypostatic to the epistatic allele. Often involves pathway where expression of 1 allele is dependent on function of another gene. Recessive epistasis - epistatic allele is recessive, dominant epistasis - epistatic allele is dominant. Population = a group of organisms of the same species inhabiting the same area at the same time. Gene pool = sum of all the alleles in a population. Allele frequency = rate at which a particular allele appears within a population. 1 of 3 Chi-Squared Used to compare observed phenotypic ratios w/ expected ratios. Tells you if difference b/w observed and phenotypic ratios are due to chance. Used when: Variation is discrete, not continuous. Data is in whole numbers. Before chi-squared test, a null hypothesis is formed. H0 - There is no significant difference b/w observed and expected data, the difference is due to chance. Chi-squared used to accept/reject null hypothesis. Calculate the degrees of freedom. Degrees of freedom = the number of categories (e.g. phenotypes) − 1. Find the critical value that corresponds to the degrees of freedom in a probability distribution table at 0.05 significance level. χ=ΣE(O−E)2 O = observed values. E = expected values. If chi-squared is lower than critical value accept null hypothesis. Predictions of phenotypic ratios are rarely correct due to random fertilisation. 2 of 3 Hardy-Weinberg Principle Hardy-Weinberg principle predicts allele frequencies won't change from generation to generation - population's allele + genotype frequencies are inherently stable. Assumes: no mutations, migrations or emigrations; no selective pressure for/against a geneotype; and that the population size is infinite. p+q=1 or p^2+2pq+q^2=1 - p^2=pp = homozygous dominant, q^2=qq=homozygous recessive, etc. 3 of 3
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