4.10 Expression of a Single Gene May Have Multiple Effects

Multiple Choice

Pleiotropy refers to:
a) Multiple genes affecting a single trait.
b) One gene affecting multiple phenotypic traits.
c) A single gene having only one effect.
d) Environmental effects on gene expression.

b

True or False

A mutation in one gene that causes multiple, seemingly unrelated effects is an example of pleiotropy.

true

Multiple Choice

Which of the following disorders is caused by a mutation in the FBN1 gene that encodes the connective tissue protein fibrillin?
a) Porphyria variegate
b) Marfan syndrome
c) Cystic fibrosis
d) Phenylketonuria

b

Short Answer

What type of mutation causes Marfan syndrome, and what is its mode of inheritance?

An autosomal dominant mutation in the FBN1 gene.

Multiple Choice

Which of the following symptoms would not be associated with Marfan syndrome?
a) Weak aorta
b) Lens dislocation in the eyes
c) Brittle bones due to collagen deficiency
d) Long limbs and tall stature

c (Marfan affects fibrillin, not collagen)

Multiple Choice

Porphyria variegate is an example of:
a) A polygenic trait
b) A pleiotropic autosomal dominant disorder
c) A sex-linked recessive disorder
d) A chromosomal translocation

b

Short Answer

What causes the symptoms in porphyria variegate at the molecular level?

Inadequate metabolism of the porphyrin component of hemoglobin, leading to a toxic buildup of porphyrins in the body.

Multiple Choice

The symptoms of porphyria variegate may include all of the following except:
a) Abdominal pain
b) Muscular weakness
c) Fever and racing pulse
d) Enhanced oxygen-carrying capacity

d

True or False

Both Marfan syndrome and porphyria variegate are caused by autosomal dominant mutations that affect multiple body systems.

true

Short Answer

Explain how pleiotropy demonstrates that a single gene can influence multiple organ systems.

Because one gene’s product (such as fibrillin or a porphyrin enzyme) may function in many tissues, a mutation in that gene disrupts multiple physiological pathways, leading to multiple phenotypic effects