BIOL 2000 Lecture Notes - Meiosis, Mendelian Inheritance, Zygosity

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8 Feb 2013
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Chapter 4a-1
Mapping Eukaryote Chromosomes by Recombination
Defintitions:
Recombinant product- a product of meiosis that differs from the haploid
genotypes that give rise to the diploid meiocyte
Parental product- a product of meiosis that is the same as the haploid
genotypes that gave rise to the diploid meiocyte
Dihybrid- an individual heterozygous at two genes
Coupling configuration- arrangement of linked alleles in dihybrid such that
the two dominant alleles are on one chromosome, the two recessive alleles
are on the other chromosome (AB/ab)
Repulsion configuration- arrangement of linked alleles in a dihybrid such
that the a dominant and a recessive allele are together on each chromosome
(Ab/aB)
Cis dihybrid- a dihybrid in which the alleles are coupled
Trans dihybrid- a dihybrid in which the alleles are in repulsion
Map unit- the distane between two genes where one product of meiosis out
of 100 is recombinant
Gene locus- the position of a gene within the genome
Linked- two genes that are on the same chromosome
Linkage group- a set of genes that are on the same chromosome
Unlinked- two genes that assort independently *( a/a ; B/b) either on
different chromosomes or >50cM apart on the same chromosome
CentiMorgan- cM is equal to 1% recombinant progeny
Trihybrid- an individual heterozygous at three genes
Interference- a measurement of the degree to which a cross-over in one
interval inhibits a cross-over in a second interval
Linear tetrad- a tetrad resulting from meiosis in which sister products are
adjacent to one another
First division segregation (MI) a linear array of tetrads (4:4) produced
from a heterozygous meiocyte, when the alleles separate after Meiosis I;
indicative of no crossovers between the gene and centromere
Second division segregation (MII)- a linear array of tetrads (2:2:2:2)
produced from heterozygous meiocyte when the alleles separate after
Meisosis II; indicative of a crossover between the gene and centromere
Objective 1: Recognize how linkage changes the expectation of Mendel’s
second law
Punett square
o Expected segregation of P and L
1:1:1:1 ratio of dihybrid test cross progeny
9:3:3:1 ratio of dihybrid F2 progeny
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