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15 Cards in this Set

  • Front
  • Back
Mendel's 2nd Law
The Principle of Independent Assortment
traits (alleles) for different characters (genes) assort independently
interchromosomal recombination
recombination of alleles at loci located on separate, non-homologous chromosomes due to random alignment of homologous pairs along the Metaphase plate

p(P)=p(R)
intrachromosomal recombination
recombination of alleles at loci located on the same homologous chromosome pair due to crossing over during Prophase I
dihybrid (two-point) test cross
expected results of a two-point (heterozygous at two loci) test cross with independent assortment
1:1:1:1 geno and pheno

p(P)=p(R)
p(AB)+p(ab)=p(Ab)+p(aB)
syntentic genes
genes located on the same chromosome, may or may not assort independently

may or may not be linked depending on distance between genes (>50 cM not linked)
linked genes (linkage group)
genes located close together on the same chromosome that do not assort independently

crossing over does not happen in every meiotic event
unlinked linked loci expected

completely linked loci expected
equal parental and recombinant combinations

only parental combinations
linkage notation
cis-configuration (coupling phase)

trans-configuration (repulsion phase)
heterozygous individuals have only dominant (wild type) or recessive (mutant) alleles on the same chromosome (MD/md)

heterozygous individuals have one dominant (wild type) and one recessive (mutant) allele on the same chromosome (Md/mD)
linkage mapping

recombination frequency

linkage distance

linkage map
p(P)>p(R)

% recombinant progeny= # recomb/# total prog)*100

% recomb (in centiMorgans (cM) or map units (m.u.))

a genetic map indicating linkage (relative) distances between loci based on recombination freq
double crossovers
not detected because they are not associated with a distinct phenotypic class

distances between genes are underestimated. As the distance increases, the accuracy decreases due to multiple double crossover event.
three-point test cross (trihybrid individual)
heterozygous genotype, dominant (wild type) phenotype X homozygous recessive (mutant)

double crossovers can lead to a distinct phenotypic class

p(P) always most freq.
p(DCO) always least freq
locus that differs btw parent and DCO is middle
coefficient of coincidence (C.O.C)

interference
crossover between tow loci inhibiting additional crossovers between adjacent two loci
#obs DCO/#expected DCO

degree to which inhibition occurs
1-COC
genetic mapping

molecular (DNA) markers
determine distance between loci based on correlations between phenotypic traits and markers

variation (phenotypically netural) in DNA sequences
quantitative trait loci (QTL) mapping
distance between genes estimated from linkage between quantitative trait variation and molecular (DNA) markers
physical maps

karyotype analysis

fluorescent in situ hybridization (FISH)
physical location of genes on chromosomes

correlations between G-banding patterns and phenotypes

tag genes with fluorescent probes