Question

question 26
what is true about a carrier of a recessive disorder?
gene with instructions for light - sensitive proteins within the eye
two alleles possible:
r (produces functioning light - sensitive proteins)
r (produces defective light - sensitive proteins)
to be color - blind...
male must inherit color - blindness allele (r) from his mother.
female must inherit color - blindness allele (r) from both parents.
to have normal vision...
male must inherit normal color - vision allele (r) from his mother.
(carrier) female can inherit normal color - vision allele (r) from either her mother or her father.

a the carrier has two copies of the allele and exhibits symptoms.
b the carrier has one copy of the allele and exhibits symptoms.
c the carrier has two copies of the allele and does not exhibit symptoms
d the carrier has one copy of the allele and does not exhibit symptoms.

Explanation:

To determine the correct answer, we analyze the diagram and the concept of carriers in recessive disorders (like X - linked color blindness here). A carrier of a recessive disorder has one copy of the recessive allele (that causes the disorder) and one normal allele. Since the normal allele is dominant, the carrier does not exhibit the symptoms of the disorder.

• Option a: Carriers do not have two copies of the recessive allele (that would make them affected, not carriers) and they don't exhibit symptoms. So this is wrong.
• Option b: Carriers have one copy of the recessive allele but do not exhibit symptoms (because of the dominant normal allele). So this is wrong.
• Option c: Carriers have one, not two, copies of the recessive allele. So this is wrong.
• Option d: Matches the definition of a carrier - one copy of the recessive allele and no symptoms.

Answer:

d. The carrier has one copy of the allele and does not exhibit symptoms