Question

which of the following best explains why different cells (like skin cells and nerve cells) have different functions even though they have the same dna?
a different chromosomes are active in different cells
b cells lose unnecessary dna over time
c some cells copy their chromosomes more than others
d gene expression varies depending on the cell type

Explanation:

• Option A: All cells (except gametes) in an organism have the same set of chromosomes. So, different chromosomes being active is not the reason.
• Option B: Cells do not lose DNA over time. The DNA content (except in cases like programmed cell death - apoptosis which is a different scenario) remains the same in somatic cells.
• Option C: Chromosome copying (DNA replication) occurs in a highly regulated manner during cell division. The number of chromosome copies (in terms of ploidy) is consistent for a given cell type (except in cases of mutations or abnormal cell division which are not the norm for explaining normal cell - function differences).
• Option D: Gene expression is the process by which genes are transcribed and translated to produce proteins. Different cell types (like skin and nerve cells) express different subsets of genes. For example, nerve cells express genes related to neurotransmitter synthesis and signal transduction, while skin cells express genes for keratin production. This variation in gene expression leads to different functions.

Answer:

D. Gene expression varies depending on the cell type