In your body, why do muscle cells and skin cells look and behave differently?

Question

A.
They have different genes.

B.
Their genes are being expressed differently.

C.
The same genes are being expressed in both types of cells.

D.
There is no similarity in their chromosomes.

Answer 1

Again, just take a second to look at the question. Even if you know nothing about the subject, you can still figure out the right answer for this question. A, C, D are the same line of logic, so none of them can be right in this type of question. Thus by elimination, B, is right.

A says 'different genes', while D says 'no similiarity in chromosomes'. Since you know that genes are on chromosomes, this is basically the same answer. SImiliarly, C says 'same genes are being expressed in both types of cells', well that wouldn't lead to variation, would it?

The mechanism of cellular diversity is through differential gene expression. All cells of a multicellular organism have the same gene content (but can vary in the ploidy number, depending on it's position in the cell cycle). How do tissues become differentiated? It happens early in development, and the location of the cell becomes key. Read Gilbert's Developmental Biology if interested in more detail. (link below)

Answer 2

I'll go for B