Lecture 6

Question 1

heterozygous for linked genes A and B

Answer 1

AB/ab

Question 2

three point testcross

Answer 2

a test cross for three genes

Question 3

double crossover recombinant chromosomes

Answer 3

• the outer two alleles are the same but the middle allele is different from the nonrecombinant
• also has the smallest number of progeny

Question 4

nonrecombinant

Answer 4

• has the largest number of progeny

Question 5

Steps in working a three point test cross

Answer 5

1) identify NCOs (most numerous)
2) identify DCOs (least numerous)
3) compare NCO to DCO. should differ in only one characteristic
4) The characteristic that differs is the middle gene. Put it in the middle if it is not already
5) find SCO1 (differ by first gene) and SCO2 (differ by third gene)
6) calculate recombination frequency (SCO1+DCO)/total (SCO2+DCO)/total
7) sum the two for map distance

Question 6

coefficient of coincidence

Answer 6

(#observed of DCO)/(#expected DCO)

calculate expected DCO by multiplying the two recombination frequencies and then multiplying by the total

Question 7

interference

Answer 7

1-C=# observed due to interference