AP Biology · Topic 5.4
Non-Mendelian Genetics Practice
Part of Heredity.(IST-1.F)
Practice questions
23
Sample questions
5 of 23 — sign in to practice the rest with adaptive difficulty and mastery tracking.
Sample 1difficulty 1/5
A bell-shaped distribution like this is best explained by:
- Acheck_circle
Polygenic inheritance with additive contributions from multiple gene loci.
- B
Mitochondrial inheritance.
- C
Strict Mendelian dominance with two phenotypic classes.
- D
Sex linkage.
Why
Continuous variation across many phenotypic classes arises when many genes contribute small additive effects, often with environmental modifiers.
- A
Sample 2difficulty 1/5
What does this bell-shaped phenotypic distribution most likely indicate?
- A
Mitochondrial inheritance.
- B
Single-gene Mendelian inheritance.
- C
Sex linkage.
- Dcheck_circle
Polygenic inheritance with environmental contribution producing a continuous trait.
Why
Continuous traits like height and skin color result from many genes acting additively; environmental influence further blurs categories, producing the smooth normal distribution.
- A
Sample 3difficulty 1/5
Which best describes the phenomenon shown?
- A
Polygenic inheritance: many genes contribute additively to one trait.
- B
Codominance: heterozygotes display both alleles.
- Ccheck_circle
Pleiotropy: a single gene influences multiple, seemingly unrelated phenotypic traits.
- D
Linkage: alleles travel together due to physical proximity.
Why
Pleiotropy occurs when a single gene affects multiple traits (e.g., the CFTR gene affecting lung, pancreatic, and reproductive function in cystic fibrosis).
- A
Sample 4difficulty 2/5
An affected mother (filled circle) has children with an unaffected father; all three children (regardless of sex) are affected.
Which mode of inheritance best fits the pedigree?
- A
Autosomal recessive
- B
Y-linked
- Ccheck_circle
Mitochondrial
- D
X-linked dominant
Why
Mitochondrial DNA is maternally inherited: an affected mother transmits the trait to ALL her offspring, while affected fathers do not pass it on.
- A
Sample 5difficulty 2/5
Coat color in Labradors involves two genes. The B locus controls pigment (B black, b brown). The E locus controls deposition (E pigment deposited, ee no deposition resulting in yellow regardless of B).
The 9:3:4 ratio indicates which type of gene interaction?
- A
Codominance between B and E.
- B
Independent assortment producing a 9:3:3:1 ratio.
- C
Incomplete dominance at the E locus.
- Dcheck_circle
Recessive epistasis: ee masks expression at the B locus.
Why
Homozygous ee blocks pigment deposition regardless of B genotype, masking the B-locus phenotype. The combined yellow class (3 BbEe-yellow + 1 bbee-yellow = 4) yields the modified 9:3:4 ratio characteristic of recessive epistasis.
- A