BIOL 1113 Lecture Notes - Lecture 18: Gamete, Allele, Chromosome
12 Dec 2017
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Linkage: when two genes are on the same chromosome, likelihood that alleles will move over from one chromosome to another is related to how far apart they are. If two genes are right beside each other, the likelihood of them crossing over is much smaller. Effect on inheritance pattern: breakage/rejoining normal; occurs ~3 or 4 times for each chromosome isn"t rate, almost a given. If two genes far apart on same chromosome likely that break will occur between them, sometimes >1: new arrangements of alleles/genes are called recombinants. Two separate sets: four gamete types can get mixing up of homologues and new combination of alleles, movement of homologues that move along chromosomes are a random event made in equal proportions (25% each): no linkage. If you cross these gametes with homozygous recessive, they will be of equal proportions: assuming dominant/recessive alleles, what mendel saw in his crosses how he got 3:1 ratio in phenotypes.
