Epigenetics is the study of how external environments affect gene expression, leading to changes in genotypes and phenotypes without a change in the underlying DNA sequence. Two common epigenetic mechanisms are DNA methylation and histone acetylation, both of which affect the packaging of DNA around histone proteins, as illustrated in Figure 1 below.
Figure 1: Methyl groups on DNA and acetyl groups on histone tails influence gene expression. "Epigenetic Control: Regulating Access to Genes within the Chromosome - Boundless Open Textbook." Boundless. OpenStax College, 16 Oct. 2013. Web. 25 July 2016.
Honey bee populations are a classic example of epigenetic phenomena because genetically—identical females develop into two significantly different castes: worker bees and queen bees. All female bees are diploid, but there are major morphological, physiological and behavioral differences between queen bees and worker bees. Queen bees are the only bees in the colony that can reproduce, and worker bees are sterile and responsible for feeding and maintaining the colony.
Among the worker caste, there are two subcastes, which are nurses and foragers. The subcaste that a worker bee belongs to depends on its age, with all workers starting out as nurse bees that feed the larvae, clean the colony, and tend to the queen. As they get older, worker bees gradually shift to exclusively foraging duties like obtaining pollen and nectar resources from the environment and bringing it back to the hive.
Which of the following is the MOST plausible explanation for the shift in worker bees' duties during their lifetime?
Elimination Tool
Select one answer
A
As honey bees age, they experience a natural increase in gene expression, particularly in coding regions responsible for caretaking and housekeeping duties.
B
Histone acetylation decreases the availability of genes coding for caretaking and housekeeping duties to transcription and translation.
C
The DNA methylation pattern between nurses and foragers is different. DNA methylation decreases in worker bees as they age, particularly in coding regions responsible for caretaking and housekeeping duties.
D
The DNA methylation pattern between nurses and foragers is different. DNA methylation increases in worker bees as they age, particularly in coding regions responsible for caretaking and housekeeping duties.