Question

In humans, the allele for dimples (d) is dominant to the allele for no dimples (d). at another gene locus, the allele for broad eyebrows (b) is dominant to the allele for slender eyebrows (b). these two allele pairs assort independently. a man who is heterozygous for both traits marries a woman who has no dimples and who is heterozygous at the gene locus controlling eyebrow width. complete the sentences about this cross with the correct terms.

Answer 1

Answer:

Genotype of offspring are –  

DdBB – 2

DdBb – 4

ddBB -2

ddBb – 4

Ddbb – 2

ddbb-2

Phenotype –  

Dimple & broad eyebrow-  6 (6/16)

Dimple & slender eyebrow- 2 (2/16)

No dimple & broad eyebrow- 6(6/16)

No dimple & slender eyebrow - 2(2/16)

Explanation:

Given -

Allele for dimples (D) is dominant to the allele for no dimples (d)

Allele for broad eyebrows (B) is dominant to the allele for slender eyebrows (b)

Male is heterozygous to both the traits. His genotype would be DdBb

woman who has no dimples and who is heterozygous at the gene locus controlling eyebrow width. Her genotype would be ddBb

Cross between the two i.e DdBb and ddBb gives the following offspring

DdBb and ddBb

DB         Db         dB         db

dB DdBB DdBb ddBB ddBb

dB DdBB DdBb ddBB ddBb

db DdBb Ddbb ddBb ddbb

db DdBb Ddbb ddBb ddbb

 

Genotype of offspring are –  

DdBB – 2

DdBb – 4

ddBB -2

ddBb – 4

Ddbb – 2

ddbb-2

Phenotype –  

Dimple & broad eyebrow-  6 (6/16)

Dimple & slender eyebrow- 2 (2/16)

No dimple & broad eyebrow- 6(6/16)

No dimple & slender eyebrow - 2(2/16)

Answer 2

Assuming you mean to type:

 

"In humans, the allele for dimples (D) is dominant to the allele for no dimples (d). at another gene locus, the allele for broad eyebrows (B) is dominant to the allele for broad eyebrows (b)."

 

Man: Heterozygous for both genes means DdBb

Woman: no dimples, and heterozygous for slender eye-brows means ddBb

 

Punnett Square

 

         DB       Db         dB        db

dB   DdBB   DdBb    ddBB    ddBb

dB   DdBB   DdBb    ddBB    ddBb

db    DdBb    Ddbb    ddBb    ddbb   

db    DdBb    Ddbb    ddBb    ddbb   

 

Interpretation: anywhere that has a capital letter has the dominant trait.

Dimples+Broad eyebrows : 6 cases out of 16  (3/8=37.5%)

Dimples+slender eyebrows: 2 cases out of 16  (1/8=12.5%)

No dimples+Broad eyebrows: 6 cases out of 16 (3/8=37.5%)

No dimples+slender eyebrows: 2 cases out of 16 (1/8=12.5%)