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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
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interchromosomal recombination
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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) |
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intrachromosomal recombination
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recombination of alleles at loci located on the same homologous chromosome pair due to crossing over during Prophase I
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dihybrid (two-point) test cross
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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) |
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syntentic genes
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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) |
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linked genes (linkage group)
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genes located close together on the same chromosome that do not assort independently
crossing over does not happen in every meiotic event |
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unlinked linked loci expected
completely linked loci expected |
equal parental and recombinant combinations
only parental combinations |
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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) |
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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 |
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double crossovers
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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. |
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three-point test cross (trihybrid individual)
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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 |
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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 |
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genetic mapping
molecular (DNA) markers |
determine distance between loci based on correlations between phenotypic traits and markers
variation (phenotypically netural) in DNA sequences |
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quantitative trait loci (QTL) mapping
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distance between genes estimated from linkage between quantitative trait variation and molecular (DNA) markers
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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 |