4.12 — Sex-Limited and Sex-Influenced Inheritance

Multiple Choice

In sex-limited inheritance, the expression of a gene is:
a) Found only on the X chromosome
b) Controlled by environmental temperature
c) Limited to one sex, even if both carry the gene
d) Found only on the Y chromosome

c

True or False

In sex-limited inheritance, only males possess the gene that produces the limited phenotype.

False — both sexes can carry the gene, but only one sex expresses it due to hormonal differences.

Multiple Choice

Which of the following is an example of sex-limited inheritance?
a) Male pattern baldness in humans
b) Cock-feathering in domestic fowl
c) Red-green color blindness
d) Marfan syndrome

b

Short Answer

What determines whether a sex-limited trait (like cock-feathering in chickens) is expressed?

The organism’s sex hormones — they regulate gene expression so that the phenotype appears only in one sex (e.g., males with genotype hh).

Multiple Choice

In sex-influenced inheritance, the phenotype:
a) Is expressed only in males
b) Is controlled by genes on the Y chromosome
c) Depends on the individual’s sex hormones, even though the gene is autosomal
d) Is always dominant in females

c

True or False

In sex-influenced inheritance, the same genotype can produce different phenotypes in males and females.

true

Multiple Choice

Pattern baldness in humans is an example of:
a) X-linked inheritance
b) Sex-limited inheritance
c) Sex-influenced inheritance
d) Y-linked inheritance

c

Multiple Choice

In human pattern baldness, the genotype Bb causes baldness in males but not in females. This shows that:
a) The gene is sex-limited
b) Hormones influence the gene’s expression
c) The gene is located on the X chromosome
d) The gene is recessive in both sexes

b

Short Answer

Explain the difference between sex-limited and sex-influenced inheritance.

Sex-limited: Trait appears only in one sex, even though both may carry the gene (e.g., cock-feathering in male chickens).

Sex-influenced: Trait appears in both sexes, but the expression or dominance pattern differs between males and females (e.g., baldness in humans).

True or False

Both sex-limited and sex-influenced traits are typically controlled by autosomal genes, not sex-linked ones.

true