Bilogy sat question?

Question

In a human, the inability to synthesize the enzyme necessary for the normal metabolism of phenylalanine most likely results from

1. a gene mutation on the DNA molecule

2. an abnormal number of s*x chromosomes

3. a chromosomal alteration cause by nondisjunction

4. the condition known as Down's syndrome.

Which number is the answer?

Answer 1

Use you basic knowledge of bio to figure this out - in order to metabolize phenylalanine, a specific enzyme needs to be made.  An enzyme is a type of protein.  People who have phenylketonuria, or the inability to process phenylalanine lack this protein.

Which of your choices most directly affects the making of proteins (as in transcription and translation)?

1. a mutation (change in the bases on a chromosome)

2. number of s*x chromosomes

3. too many or too few autosomes when the chromosomes don't separate into daughter cells correctly

4. a condition cause by having an extra chromosome

If you can reason out this type of problem with what you already know, it makes the SAT questions easier.

If you're still stumped, read the link below.