Question

It's another boring day at Hotellgene Incorporated, but you willingly come to work because genetics is your life, and besides you couldn't let your boss down. You set to work crossing red and white beans as part of your experimenting. The beans that you are using are both homozygous for their respective traits. Thinking that this will be an easy cross, you write down in your lab book that the offspring will probably be all red. You assume that red is dominant and white is recessive, but after you do that cross you get some amazing results. Your results: all pink beans. Being the resourceful scientist that you are, you take the pink beans and cross them. As a result you get a phenotypic ratio of 1 red to 2 pink to 1 white. How are you going to explain these results to your boss? The phenotypic ratio is not the expected 3:1.

1. What is the genotype of the red beans?

A. RR

B. Rr

C. rr

2. What is the genotype of the white beans?

A. RR

B. Rr

C. rr

3. What is the genotype of the pink beans?

A. RR

B. Rr

C. rr

4. What is the inheritance pattern observed in this problem?

A. Polygenic inheritance

B. Pleiotropy

C. Incomplete dominance

D. Codominant inheritance

Answer 1

Answer No 1:

The genotype of the red beans will be RR. As red is the dominant trait, it will be written in capital letters.

A dominant trait is the one which suppresses the effect of a recessive trait. A recessive trait is the one which gets masked by the dominant trait.

Answer No 2:

The genotype of the white beans will be rr. As white beans are considered as a recessive trait, hence it will be written in small alphabets.

As explained earlier, a recessive trait gets marked by a dominant trait. For a recessive trait to express its phenotype, both the alleles of a gene should be recessive.

Answer No 3:

The genotype of the pink beans will be Rr.

r r

R Rr Rr

R Rr Rr

Answer No 4:

The correct option is C.

Incomplete dominance can be described as a trait which occurs when a dominant trait is not dully dominant over the recessive trait. As a result, offsprings are produced which have a phenotype which is a blending of both the dominant and recessive phenotypes. Such an effect is known as incomplete dominance.