I think the answer is (e) but I'm not certain.
In Drosophila melanogaster the genes for yellow body colour and white eye colour are linked this means that:
a. They can produce only one phenotype
b. They cannot separate
c. They produce more parental types than recombinant types
d. They produce more recombinant types than parental types
e. They produce only homozygotes
Although this is not my area of expertise, I would assume that anything "linked" cannot be separated.
To determine the correct answer, let's break down the given information about the genes for yellow body color and white eye color in Drosophila melanogaster.
The statement says that the genes for yellow body color and white eye color are "linked." Genes that are linked are located on the same chromosome, which means that they are physically close to each other. This physical proximity affects their inheritance pattern.
Now, let's evaluate each option based on this information:
a. They can produce only one phenotype: This option states that the linked genes can produce only one phenotype (observable characteristic). This is unlikely because traits are usually influenced by multiple genes, and it is possible to have different phenotypes even with linked genes. Therefore, option a is unlikely to be the correct answer.
b. They cannot separate: This option implies that the linked genes cannot segregate during meiosis, which is not true. Linked genes can separate during meiosis through the process of recombination. Therefore, option b is unlikely to be the correct answer.
c. They produce more parental types than recombinant types: This option suggests that during recombination, the linked genes produce more offspring with the same combination of alleles as the parents (parental types) than offspring with new combinations of alleles (recombinant types). This aligns with the concept of linked genes, as physical proximity on the same chromosome increases the likelihood of parental types being inherited together. Therefore, option c is a possible correct answer.
d. They produce more recombinant types than parental types: This option proposes the opposite of option c, stating that linked genes produce more offspring with new combinations of alleles (recombinant types) than offspring with the same combination of alleles as the parents (parental types). This is unlikely because linked genes tend to stay together more often. Therefore, option d is unlikely to be the correct answer.
e. They produce only homozygotes: This option suggests that the linked genes can only produce individuals that are homozygous (having the same alleles for a trait). However, linked genes can also produce heterozygotes (having different alleles for a trait) through recombination. Therefore, option e is unlikely to be the correct answer.
Based on our analysis, option c, "They produce more parental types than recombinant types," seems to be the most likely correct answer.