Question

Green seed color is dominant (g), and yellow seed color is recessive (g). Which of the following genotypes will cause yellow seeds?

1) GG
2) Gg
3) gg
4) Cannot be determined

Answer 1

The genotype that causes yellow seeds in pea plants is 'gg'. A cross between RrYY and rrYy results in four squares in a Punnett square and produces round yellow or round green seeds based on Mendelian genetics. True-breeding crosses between green and yellow seeds yield 100 percent yellow F1 offspring.

Step-by-step explanation:

In genetics, green seed color is dominant (G) and yellow seed color is recessive (g). To have yellow seeds, the genotype must be homozygous recessive, which is gg. Therefore, the genotype that will cause yellow seeds is option 3) gg.

In a cross between RrYY and rrYy pea plants, the possible genotypes are RrYy, Rryy, and the phenotypes are round yellow seeds and round green seeds. For the Punnett square analysis of this cross, four squares are needed because the Rr heterozygous genotype has a separate allele for the seed shape, and Yy has separate alleles for the seed color, making a 2x2 Punnett square.

When true-breeding parents with green seeds are crossed with true-breeding plants with yellow seeds, the F1 offspring would be expected to have 100 percent yellow seeds because the yellow seed color is dominant. This is based on Mendelian genetics where the dominant allele expresses the trait in the presence of a recessive allele.