Question

Suppose there are two genes on two different chromosomes, one gene called G and the other called D. An individual has the genotype GgDd. Which of the following drawings correctly shows cells in this individual after DNA replication but before cell division of the first meiosis? Assume no recombination/crossing-over occurs between the chromosomes.

Answer 1

Answer:

as the question does not contains image i have  already mentioned the link to image in ask for detail section therefore i will answer according to that image.

the answer is "B"

Explanation:

Because before crossing over but after duplication both chromosomes will have same alleles as GgDd therefore according to the image the answer will be option "B". as this option showed duplicated chromosomes.

Answer 2

Answer:

The question lacks the image, the image has been added as an attachment.

Based on the attached image, the correct answer is A

Explanation:

DNA replication is the duplication of the genetic material (DNA) found on chromosomes in cells. It results in the production of two identical chromosomes bound together at the centromere. These chromosomes are collectively called SISTER CHROMATIDS and they are identical in the sense that they contain the same alleles of the same gene unlike homologous chromosomes which may contain different alleles of the same gene.

Gene G and D found on the chromosomes undergoes replication to result in exactly the same type of allele in the replicated chromosome as in the template i.e. Allele G will result in allele G on the replicated chromosome or sister chromatid while allele g will result in allele g on the chromatid. The same applies for alleles D and d.

It is important to note that alleles G and g are found on homologous chromosomes i.e similar but non-identical chromosomes received from each parent. They are not identical because they have different alleles.

The dark spot in between the two replicated chromosomes is the CENTROMERE, and it binds the two sister chromatids together.

The question says the two genes are found on different chromosomes. This is evident in option A as we can see the distinct chromosomes carrying the two genes. Option D is a chromosome with the genes on different loci.

Options A and B are wrong because the alleles on each chromatid are different meaning they are not even sister chromatids. This opposes the result of DNA replication. An allele G cannot have an allele g as a replicated pair, same goes for D.