Question

Normal maize has starchy seeds which remain smooth when dry. A mutant form has sugary seeds which go wrinkled when dry. When a mutant was crossed with a normal plant, a F${}_1$ was produced which had smooth seeds. What would be the relative ratios of the different seed types, if the F${}_1$was allowed to self?

• A. 1 smooth : 3 wrinkled
• B. 3 smooth : 1 wrinkled
• C. 1 smooth : 1 wrinkled
• D. All wrinkled

Answer 1

The correct option is B 3 smooth : 1 wrinkled

Suppose the genotype of a normal plant with smooth seeds is SS and that of wrinkled seeds is ss. For a cross between SS and ss, all the offsprings produced will have genotype Ss (smooth seeds). If the F${}_1$ with smooth seeds Ss is allowed to self, then 3 smooth and 1 maize plant with wrinkled seeds will be formed.

Genotypes Ss (smooth seeds) X Ss (smooth seeds)

Punnette square

Gametes	S	s
S	SS	Ss
s	Ss	ss

As is evident from Punnette square, 3 plants with smooth seeds and 1 with wrinkled seeds are formed.