Chapter 7- linkage, recombination and eukaryotic gene mapping

what is the principle of segregation?

two alleles at a locus separate in meiosis and one allele passes into each gamete

what is the principle of independent assortment?

two alleles at a locus separate independently of alleles at other loci

what is recombination?

sorting of alleles into new combinations

what are linked genes?

genes located close together on the same chromosomes, these belong to the same linkage group

how do linked genes travel?

they travel together and arrive at the same gamete, these don't assort independently

describe the relationship between crossing over and linkage

they have opposite effects- linkage keeps them together and crossing over mixes them up

what is complete linkage?

located very close together on the same chromosomes and do not exhibit crossing over

what are produced with complete linkage?

only non-recombinant progeny

what are produced with independent assortment?

half the progeny are recombinant and half are non- recombinant

what is the ratio for independent assortment?

1:1:1:1

how do you find recombination frequency?

number of recombinant progeny/total number of progeny x 100

what is coupling (cis configuration)?

wild-type alleles are found on one chromosomes, mutant alleles are found on the other chromosome

what is physical gene mapping?

chromosome maps calculated using physical distances along the chromosomes

describe a three-point test cross

more efficient mapping technique, order of three genes can be established in a single set of progeny, some double crossovers can usually be detected, and provides more accurate map distances

when recombinant chromosomes have a double crossover what happens?

only the middle genes is altered

what does a three-point test cross determine?

gene order and location of crossover

what are RFLPs?

restriction fragment length polymorphisms

what is GWAS?

genome-wide association studies

what is important about GWAS?

association within populations, haplotype, and linkage disequilibrium

what is a haplotype?

a specific set of linked alleles

what is linkage disequilibrium?

nonrandom association between alleles in a haplotype

what does somatic cell hybridization require?

requires the fusion of different types of cells

what is heterokaryon?

the resulting cell with two nuclei in somatic cell hybridization

if the gene of interest is in the region of deletion what happens?

half of the progeny will display the mutant phenotype

if the gene of interest is not in the region of deletion what happens?

all of the progeny will display the wild-type phenotype

what is FISH?

fluorescence in situ hybridization

describe FISH

uses a single-stranded complementary DNA probe for the gene and determines chromosomal location of a particular gene

describe recombination rates

they vary widely in species, chromosomes of a species, and between males and females

where in humans are recombination hotspots?

found near but not within active genes

For single crossovers, the frequency of recombinant gametes is half the frequency of crossing over because...

each crossover takes place between only two of the four chromatids of a homologous pair