Which of the following best describes the genotypes of the offspring when Mendel crossed true-breeding (pure-breeding) yellow seed plants with true-breeding green seed plants?
A) The offspring had a combination of yellow and green seeds.
B) The offspring were made up of a combination of yellow and green alleles.
C) The offspring had green seeds.
D) The offspring had yellow seeds.
Not knowing how they would interact, I would say B.
To determine the genotypes of the offspring when Mendel crossed true-breeding yellow seed plants with true-breeding green seed plants, we need to understand Mendel's laws of inheritance.
Mendel's laws state that for each inherited trait, an organism carries two alleles, one inherited from each parent. These alleles can be either dominant or recessive. In this case, let's assume that yellow seed color is dominant (allele Y) and green seed color is recessive (allele y).
When true-breeding yellow seed plants (genotype YY) are crossed with true-breeding green seed plants (genotype yy), we can use Punnett squares to determine the genotypes of the offspring.
Since the yellow seed plants are true-breeding, it means they can only pass on the allele Y to their offspring. On the other hand, the green seed plants are also true-breeding, which means they can only pass on the allele y to their offspring.
In this cross, the genotype of the first generation (F1) will be Yy, as each offspring receives one allele from each parent. However, the phenotype, or physical appearance, of the offspring will be yellow because the yellow allele (Y) is dominant over the green allele (y).
Therefore, the correct answer is D) The offspring had yellow seeds.
Note: The option B) "The offspring were made up of a combination of yellow and green alleles" is not entirely accurate. While the offspring do have a combination of alleles (Yy), their physical appearance is determined by the dominant allele, resulting in yellow seeds.