Ask a New Question
Menu

The allele for a green shell (H) is dominant to the allele for a brown shell (h)

The phenotype ratio of Generation 2 for Group R is shown in the diagram.

Which genotype could be placed in both boxes in Generation 1 that would would produce the phenotypes shown in Generation 2.

Group A. Generation 1

B. Generation 2

R

Green

Green

Green

Green

Green

Brown

(1 point)

This cannot be determined with the information provided

Ohh

Hh

OHH

1 answer

To determine the possible genotype for Generation 1 that could produce the given phenotypes in Generation 2 (Group R), we need to analyze the ratios of phenotypes shown in Generation 2.

You mentioned that there are:

  • 5 green shells
  • 1 brown shell

This ratio indicates that the expected phenotype ratio is approximately 5:1, which suggests that the genotype of the parents in Generation 1 should allow for a homozygous dominant or a heterozygous combination.

Given that:

  • The allele for a green shell (H) is dominant to the allele for a brown shell (h), the possible genotypes for green shells could be:
    • Homozygous dominant (HH)
    • Heterozygous (Hh)

Since the observed phenotype ratio includes both green (dominant) and brown (recessive), it rules out having two homozygous dominant parents. Thus, one parent must be homozygous and the other heterozygous or another combination that allows for brown to appear in the offspring.

Possible Genotypes for Generation 1:

  1. Hh (heterozygous parent) x Hh (heterozygous parent) would yield a genotypic ratio of:

    • 1 HH : 2 Hh : 1 hh
    • Phenotypically, that gives about a 3:1 ratio, which does not match the 5:1 observed.

  2. HH (homozygous dominant) x Hh (heterozygous parent) would yield a genotypic ratio of:

    • 1 HH : 1 Hh
    • Phenotypically, that translates to 100% green shells (which does not match the brown), thus not valid.

  3. Hh (heterozygous parent) x hh (homozygous recessive parent) yields:

    • 1 Hh : 1 hh
    • Phenotypically gives a ratio of 50% green (Hh) and 50% brown (hh), which does not match.

  4. If instead, we hypothesized the scenario as Hh (heterozygous) x Hh (heterozygous) where the excess of green results from a larger population or more H alleles existing in the gene pool potentially leads to variations, it could still output the observed ratios.

Considering the phenotypic expression ratio provided:

  • If around 5 out of 6 show green (H), it suggests more H alleles present in the first generation leading to a bias toward the dominant phenotype emerging overall from numerous crosses.

Conclusion

From the phenotypes described, the best genotype for both boxes in Generation 1 to yield the 5:1 ratio in Generation 2 Group R could likely be:

  • Hh (heterozygous) for both parents, resulting in variation that leads to the presence of brown shells, assuming significant chance tilting toward green in the dominance measure over trials.

Therefore, the answer that could be placed in both boxes in Generation 1 that would result in the specified phenotypes in Generation 2 is Hh.