Topic 3

Question 1

Gametic Disequilibrium (aka linkage disequilibrium)

Answer 1

Non-random genotypic, and hence allelic associations among loci (if there are 2 loci, nonrandom genotypic associations b/w 2 loci)

Question 2

Mendel’s First Law

Answer 2

Random segregation: alleles at a single locus segregate randomly, offspring have a 50% chance of inheriting each of a parent’s alleles (basis for H-W eq’m)

Question 3

Mendel’s Second Law

Answer 3

Independently Segregation: Alleles at different loci segregate independently, so that the inheritance of alleles at locus A is independent of the inheritance of alleles at locus B

• ->otherwise, results in gametic diseq’m (or linkage diseq’m)
• ->law holds true, if loci are located on different chromosomes
• ->if loci close together on the same chromosome, , will often be inherited as a single ‘unit’

Question 4

Gametic disequilibrium vs. Linkage disequilibrium

Answer 4

Gametic diseq’m is a broa term which include many reasons that can result in non random allelic and genotypic association among loci

- includes linkage diseq'm
- also includes migration, selection, genetic drift, etc

Question 5

Meiosis

Answer 5

process by which 4 haploid gametes are produced from a diploid parent cell (located in gonads)

Question 6

Recombination

Answer 6

The process by which sister chromosomes (not chromatids) can exchange pieces of DNA during meiosis by crossing over

Question 7

Coupling phase double heterozygotes

Answer 7

AB+ab=AaBb

Question 8

Repulsion phase double heterozygotes

Answer 8

Ab+aB=AaBb

Question 9

Recombination fraction (r)

Answer 9

the fraction of recombinant gametes an individual produces

Question 10

Range for Disequilibrium coefficient D

Answer 10

• 0.25 to 0.25

1) D=0, there is no gametic disequilibrium

Question 11

Range for recombination factor (r)

Answer 11

0-0.5

1) r=0: never any recombination
2) r=0.5: loci so far apart that they may as well be on different chromosomes (there will be no linkage disequilibrium)