A nerve cell and a liver cell in the same organism contain different combinations of proteins. Which of these statements best explains why different cells have different proteins?

Question options found from another source:

a. The different cells in an organism contain different genes

b. Each cell in an organism transcribes only the genes that the cell needs to perform its functions

c. Each cell in the organism produces the same proteins, but the ones that aren't needed are immediately digested

d. The different cells in an organism all transcribe the same genes, but their ribosomes make different proteins from them

Answer:

b. Each cell in an organism transcribes only the genes that the cell needs to perform its functions

Explanation:

Every cell in an organism contains exactly the same DNA, but it is how that DNA is put to use that affects the identity of the cell.

In a nerve cell and a liver cell the DNA is the same, but the expression of different genes, and therefore the combination of proteins present, will be hugely different.

This is because different combinations of genes are transcribed in different cell types that make one cell function as a liver cell and one as a nerve cell. These genes are cell-type specific. For example, a liver cell might express enzymes important for the breakdown of toxins, whereas a nerve cell might produce proteins important for signalling.