Sex and Meiosis

Question 1

Two Point Test Cross

Answer 1

F1 = heterozygote with all 4 alleles (test cross)

F2

• Parentals (most #of progeny)
• Recombinants

Question 2

Recombination Frequency

Answer 2

of recombinants/total

Question 3

Three Point Test Cross

Answer 3

F1 = heterozygote with all 6 alleles (test cross)

F2

• parentals
• single crossovers
• double crossovers (lowest #of progeny) B in middle

Question 4

Double Recombinations

Answer 4

• shrink map distance btwn 2 genes

- add 2 individuals = total

Question 5

Coefficient of Confidence

Answer 5

of expected = (RF1 x RF2) x Total

expected proportion of gamete with double crossovers

CoC = #of observed/# of expected

Question 6

Interference

Answer 6

crossover suppresses occurence of nearby crossover

I = 1 - Coefficient of Confidence

Question 7

Linkage

Answer 7

Parental ditype

• genotype of parents (2 same)
• no crossovers OR double crossover 2-strand

Non-Parental ditype

• not genotype of parents (2 same)
• double crossover 4-strand

Tetratype

• 4 distinct spores
• single crossovers OR double crossover 3-strand

Question 8

Linked Genes

Answer 8

Linked — PD&raquo_space; NPD

Unlinked PD = NPD

Question 9

Recombinant Frequency - Tetrad

Answer 9

(NPD + 1/2T)/Total

Question 10

Mapping Centromeres

Answer 10

1/2(#of tetrads with 2nd division event) / Total

Question 11

Double Strand Break

Answer 11

• 5’ ends degraded
• first strand invade
• form heteroduplex and double holliday junction
• 2 homologous chromosomes connected w/ bp
• repairs mismatch in heteroduplex = 3:1 segregation

Question 12

Synaptonemal Complex

Answer 12

• formed in Meiosis I
• holds 2 homologous chromosomes together
• Zipper proteins

Zip1 mutant

• recombination still occurs = Zip1 not important
• no interference = Zip1 spreads crossovers