Bio question?

Question

Gene S controls the sharpness of spines in a type of catus. Catuses with the dominant allele S have sharp spines, whereas homozygous recessive ss cactuses have dull spines. At the same time a second gene N determines whether cactuses have spines. Homozygous recessive nn cactuses have no spines at all.

With that said

The relationship between genes S and N in an example of?

A) Pleiotropy, B) Condominance, C) Epistasis, D) Incomplete dominance

2nd question with the sme sinero

If doubly heterozygous SsNn cactuses were allowed to self pollinate the F2 would segregate in which of the following ratios?

A) 1 sharp spined:2 dull-spined:1 spineless

B) 9 shap spined: 3 dull spined:4 spineless

C) 1 sharp spined: 1 dull spined:

D) 1 sharp spined: 1 dull spined: 1 spineless

E) 3 sharp spined: 1 spineless

Sorry for the long question I have no clue

Answer 1

1. C. Epistasis i.e. gene interaction because expression of Gene S depends is influenced by that of Gene N.

2. Double Heterozygote SsNn

each produces 4 types of gametes viz. SN, Sn, sN, sn

cross them using punnett square,

Progeny- 9 sharp spined; 3 dull spined; 4 no spine (i.e. choice-B)

(Ratio is different from typical 9:3:3:1 because anyone with genotype 'nn' would not have a spine so Gene S can not be expressed in them).