Question

In peas, the allele for yellow seeds (Y) is dominant to the allele for green seeds (y). What would be the genotype and phenotype ratios of offspring from a cross between Yy (heterozygous) and yy (homozygous recessive) individuals?
a. Genotype: ½ Yy : ½ yy; Phenotype: ½ yellow : ½ green
b. Genotype: all Yy; Phenotype: all yellow
c. Genotype: ½ Yy : ½ yy; Phenotype: all yellow
d. Genotype: all yy; Phenotype: all green

Answer 1

Answer: A. Genotype: 1/2 Yy; 1/2 yy. Phenotype: 1/2 Yellow; 1/2 Green.

Explanation: The answer lies in Punnett´s Square. A visual representation of Mendelian inheritance. Dominant genes always express when an organism presents them. Recessive genes express when both alleles contain the recessive gene. A heterozygote contains different alleles for the same gene (Yy). A homozygote contains the same alleles for the same gene (YY/yy), which can be a Dominant (YY) or Recessive (yy) Homozygote.

     y  |  y

Y  Yy | Yy

y   yy | yy