Ques. 10-12. You cross an Aa Bb Cc individual with an individual of genotype Aa

Question

Ques. 10-12. You cross an Aa Bb Cc individual with an individual of genotype Aa Bb CC. All genes assort independently :

10.      The number of different gam etes expected from the Aa Bb CC parent is a) 2 b) 4 c) 8 d) 16 e) 32

11.      The expected proportion of offspring of genotype Aa BB CC is a) 1/2 b) 1/4 c) 1/8 d) 1/16 e) 1/32.

12.      The number of different genotypes expected among offspring of the cross is a) 3 b) 6 c) 9 d) 18 e) 27.

13.      With complete dominance of capital letters over lower case letters, which of the following crosses will produce a 9:3:3:1 ratio of phenotypes among offspring

            a) Aa X Aa b) Aa Bb X Aa Bb c) Aa Bb X aa bb   d) AA BB X aa bb e) aa BB X Aa bb.

14.      If the B allele is dominant to the b allele, a 1:1 phenotypic ratio is expected in which of the following crosses?

            a) BB x BB b) BB x Bb c) Bb x Bb d) Bb x bb e) bb x bb.

Explanation / Answer

10. Option B is correct.

Number of gametes produced = 2^n

n = number of heterozygous alleles.

Parent = AaBbCC

n = 2

= 2^2 = 4

11. Option D is correct.

Parental cross: AaBbCC X AaBbCc

Expected number of progeny with the genotype AaBBCC = 1/2 X 1/4 X 1/2 = 1/16

12. Option E is correct.

Parental cross: AaBbCC X AaBbCc

Number of gametes: 4 X 8

Number of genotypes = 3^n

n = number of heterozygous genes; n = 3

= 3^3 = 27

13. Option B is correct.

AaBb X AaBb cross would produce the phenotypic ratio of 9:3:3:1.

14. Option D is correct.

Bb X bb cross would produce the phenotypic ratio of 1:1.

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