[17.7-8] autosomal linkage, epistasis
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what is an autosome?
the remaining 22 chromosome other than the sex chromosomes
what is autosomal linkage?
where two or more genes are carried on the same autosome
how might genes on the same chromosome be inherited together?
• if there is no crossing over • they are therefore not segregating in accordance with mendel’s law of independent assortment
what is recombination frequency?
• frequency with with a single chromosomal crossover will take place between two genes during meiosis • this is always displayed as a percentage of the total number of offspring
describe the punnett square for heterozygous characteristics
• normal 2x2 • eg. genotype = GGNN, GgNn, GgNn, ggnn
how can you map out where alleles are found on the chromosome?
• recombination freq = relative separation distance • on a horizontal line representing the chromosome, mark the two loci with the largest separation with the phenotypes • mark the possible positions of the other loci by triangluating possible psoitions
what is epistasis?
when the allele of one gene affects the expression of another in the phenotype
describe the punnet square for the F2 genotypes based on AABB and aabb parental genotypes
• 4x4 grid • gametes = AB, Ab, aB, ab • ratio = 9:3:4 (but probs depends on q)