In Drosophila, what causes the mosaic eye color in position effect variegation (PEV) when the _white_ gene is involved?
Understand the Problem
The question asks about the cause of mosaic eye color in Drosophila (fruit flies) due to position effect variegation (PEV) when the white gene is involved. PEV refers to the variable expression of a gene depending on its position, often near heterochromatin. The options provide different potential mechanisms, and the correct answer will explain how PEV leads to mosaic eye color when the white gene is affected.
Answer
Translocation of the _white_ gene to heterochromatin causes random silencing in some cells, resulting in mosaic eye color.
In Drosophila, mosaic eye color in position effect variegation (PEV) involving the white gene is caused by the gene's translocation to a heterochromatin region. This leads to random silencing of the white gene in some cells, resulting in a mosaic pattern of colored and white patches in the eye.
Answer for screen readers
In Drosophila, mosaic eye color in position effect variegation (PEV) involving the white gene is caused by the gene's translocation to a heterochromatin region. This leads to random silencing of the white gene in some cells, resulting in a mosaic pattern of colored and white patches in the eye.
More Information
Position Effect Variegation (PEV) is an epigenetic phenomenon that affects gene expression. This means the change in gene expression is not due to a change in the DNA sequence itself, but rather to other factors.
Tips
A common mistake is thinking the mutation of the white gene itself causes the mosaic phenotype, rather it is the position of the gene, which is why it is called 'position effect'.
Sources
- Position-Effect Variegation, Heterochromatin Formation, and Gene ... - pmc.ncbi.nlm.nih.gov
- Position-effect variegation - Wikipedia - en.wikipedia.org
- A high proportion of genes involved in position effect variegation ... - pmc.ncbi.nlm.nih.gov
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