Tetrad Analysis and Gene Interaction Cont.

Question 1

Codominance

Answer 1

usually involves a system in which the 2 alleles of a single gene have slightly different products, both of which appear in the expression of the phenotype; effects of both alleles are detected simultaneously

Question 2

Example of codominance

Answer 2

presence of MN blood group antigens; LmLm (blood group M) x LnLn (blood group N) has F1 generation of LmLn (blood group MN that has presence of both M and N antigens)

Question 3

Duplicate recessive epistasis

Answer 3

common mechanism is that the two genes specify enzymes that function in the same biochemical pathway

Question 4

Complementary gene action

Answer 4

products of 2 gene loci complement each other to produce a phenotype; one dominant allele at each locus is required for full expression of the phenotype; ex: White #1 x White #2 flowers produce purple flowers in the F1 crossing F1 generations w/ each other gets a F2 generation of 9 purple: 7 white

Question 5

What’s the regular ratio of a dihybrid cross?

Answer 5

9:3:3:1

Question 6

What’s the ratio of a dominant epistasis dihybrid cross?

Answer 6

12:3:1 (12 is 9+3); A_B_ + A_bb

Question 7

What’s the ratio of a recessive epistasis dihybrid cross?

Answer 7

9:3:4 (3+1); aaB_ + aabb

Question 8

What’s the ratio of a complementary dihybrid cross?

Answer 8

9:7 (3+3+1); A_bb + aaB_ + aabb

Question 9

What’s the ratio of a suppression dihybrid cross?

Answer 9

13:3 (12+1); A_B_ + A_bb and aabb are suppressed

Question 10

What’s the ratio of a duplicate genes dihybrid cross?

Answer 10

15:1 (9+3+3); A_B_ + A_bb + aaB_

Question 11

Which genotype dies in dominant lethal (rare)?

Answer 11

AA and Aa

Question 12

Which genotype dies in recessive lethal?

Answer 12

aa

Question 13

Which genotype dies in incomplete dominance lethal?

Answer 13

aa normal, Aa affected, AA embryo lethal