In peaches, the homozygous genotype G O G O produces oval glands at the base of
ID: 17836 • Letter: I
Question
In peaches, the homozygous genotype GOGO produces oval glands at the base of the leaves, the heterozygous genoytype GOGA produces round glands, and the homozygous genotype GAGA results in the absence of glands. At another locus, a gene 'S' produces fuzzy peach skin and its recessive allele 's' produces smooth skin.
a) Give the expected phenotypes and their proportions among the offspring from a mating of two GOGA Ss parents. If the round and fuzzy offspring from the first cross are randomly crossed, what is the probability that any one of their offspring has no glands and is smooth?
Explanation / Answer
a)P: oval glands and smooth (GoGoss) >< fuzzy skin and lacking glands (GaGaSS)
F1: all GoGaSs (all round-fuzzy)
Gametes: GoS, Gos, GaS, Gas
F2 (Punnet square)
Genotypic ratio: 1 GoGoSS : 2 GoGoSs : 1 GoGoss : 2 GoGaSS : 4 GoGaSs : 2 GoGass : 1 GaGaSS : 2 GaGaSs : 1 GaGass
Phenotypic ratio: 3 oval-fuzzy : 1 oval-smooth : 6 round-fuzzy : 2 round-smooth : 3 absence-fuzzy : 1 absence-smooth