BIO2008: Lecture 2 0.0 / 5 ? BiologyLecture 2UniversityOther Created by: LMoneyCreated on: 10-05-14 18:42 what is the probability of an allele equal to? its frequency 1 of 31 what does Mendel's law state? Segregation of alleles of a gene in formation of reproductive cells 2 of 31 How can you test whether genotypic ratios in offspring follow Mendelian inheritance? Chi-squared test (X^2 test)- in this case Chi-squared goodness of fit because testing against distribution 3 of 31 what are the other Chi-squared tests? Chi squared test of association, Chi squared test of homogeneity 4 of 31 should frequencies or number be used in chi-squared tests? always numbers 5 of 31 A dominant over a. In offspring of a Aa x Aa cross what is the probability of phenotype A? 75% 6 of 31 what is the most common mode of variation at the DNA level? mostly codominant 7 of 31 what are the most widely used molecular markers in population genetics? allozymes (isozymes, protein variants) 8 of 31 which DNA based methods are used in population genetics? 1) RFLP analysis 2) PCR 3) sequencing 9 of 31 how is Allozyme or DNA analysis carried out? Run an extract/PCR product of individuals on a gel: separate molecules on charge- measure differences in velocity in the gel 10 of 31 what is the Hardy Weinburg principle used for? calculate expected genotype frequencies under 'random' mating in 'ideal' population 11 of 31 what is an ideal population? diploid, sexual reproduction, nonoverlapping, generations, large populations, no effect of natural selection etc. 12 of 31 Let p be the allele frequency of A and q the allele frequency of a, what are the frequencies for the genotypes? p^2 for AA, 2pq for Aa, q^2 for aa 13 of 31 What is the maximum frequency of heterozygotes in a population? (according to Hardy Weinburg) 50% 14 of 31 what is the test for presence of HW equilibrium? Chi squared goodness of fit test 15 of 31 what does the Chi squared goodness of fit test do, in this context? Tests whether there is a significant difference between genotype numbers observed and genotype numbers expected under HW 16 of 31 how many degrees of freedom is there for 3 genotypic classes? 1 17 of 31 If the calculated chi-square value is less than the 0 .05 value in the table, what do we do with the hypothesis? we accept it, if it was greater- accept it- if we accept, means the population is in HW equilibrium 18 of 31 when can examples of the HW principle become more complicated? 1) If sex-linked (gene is on X chromosome) 2) If dominant/recessive alleles 3) If more than two alleles 4) If you have polyploids (too complicated) 19 of 31 when can deviations from HW happen? 1) Inbreeding 2) Population structure 3) Mate choice 4) Selection against/for certain genotype 20 of 31 when does inbreeding happen? 1) Plants that self-fertilise 2) Mating between related individuals 21 of 31 what happens to the genotype frequencies with inbreeding? Excess homozygote genotypes relative to the frequencies expected with random mating 22 of 31 what halves number of heterozygotes every generation? self-fertilisation 23 of 31 what lowers proportion heterozygotes in subpopulations, relative to expected? structure 24 of 31 what is assortative mating, or positive assortative mating? similar individuals mate more often than expected under random mating 25 of 31 what is disassortative mating or negative assortative mating? dissimilar individuals mate more often than expected under random mating 26 of 31 What do you predict with assortative mating? Less heterozygotes than in HW (deficit) 27 of 31 what is an example of assertive mating? flowering time differences 28 of 31 what are examples of disassortive mating? SI system in plants, MHC in mammals 29 of 31 selection with heterozygote advantage you predict to find what? More heterozygotes than expected 30 of 31 with Hybridisation, often heterozygotes less fit so you would predict to find what? Deficit heterozygotes, less 31 of 31
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