Question

The chromatin structure is dynamic. In regions of highly condensed chromatin, such as the centromere, the boundary between heterochromatin and euchromatin is variable. Genes that are near this boundary region can be influenced by either type of chromatin in what is referred to as position effects.
Recall the early Drosophila melanogaster experiments by Hermann Muller where the repositioning of the w + allele (the normal activity of the w + allele produces red-eye pigment) by translocation or inversion near this boundary of chromatin produced intermittent w + activity. In the heterozygous state (w +/w), a variegated eye is produced, with white and red patches.
Which statements are true in relation to this experiment? Select all that apply.
a. Since the genotype is heterozygous, half of the cells will receive the w + allele producing red eye patches, while the other half will receive the w allele producing white patches.
b. When heterochromatin spreading does not reach the new location of the w + allele, the gene will be transcribed, producing red eye patches.
c. When heterochromatin spreading encompasses the new location of w + allele, the gene is transcribed, producing white eye patches.
d. Even though eye color phenotypic variegation exists within the eye, all cells have the same genotype.
e. When heterochromatin spreading encompasses the new location of w + allele, the gene is not transcribed, producing white eye patches.

Answer 1

In the heterozygous state (w +/w), a variegated eye is produced, with white and red patches. The following statements are true in relation to this experiment:

b. When heterochromatin spreading does not reach the new location of the w + allele, the gene will be transcribed, producing red eye patches.

c.  When heterochromatin spreading encompasses the new location of w + allele, the gene is transcribed, producing white eye patches.

d. Even though eye color phenotypic variegation exists within the eye, all cells have the same genotype.

Explanation:

Heterochromatin in droshophila has genes which gets expressed by position effect variegation. In some normally active cells genes are silenced in some due to transposition  of genes which causes change or variegating in phenotype.

This change is due to change in position of the gene in the genome and chromosome but no change in gene.

The variegation in drsophilla melanogaster shows that white gene was not damaged.

The rearrrangement of gene takees place at pericentric heterochromatin.

Heterochromatin is required for maintaining genome integrity and regulating gene expression. When spread in neighboring region it can inactivate the genes present there.

The genes taking part in variegation remains same hence no change in genotype.