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AP Biology Practice Quiz: Non-Mendelian Genetics

Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026

Test your understanding with short quizzes. This quiz has 11 questions to check your progress.

Question 1 of 11

Which of the following best explains why many traits do not follow the simple ratios predicted by Mendel’s model of inheritance?

All Questions (11)

Which of the following best explains why many traits do not follow the simple ratios predicted by Mendel’s model of inheritance?

A) All genes are inherited from a single parent.

B) All traits are controlled by a single gene with two alleles.

C) Factors such as gene linkage, codominance, and incomplete dominance cause deviations.

D) Environmental factors are the sole determinant of an organism's phenotype.

Correct Answer: C

The provided content explicitly states that 'Many traits do not follow Mendelian ratios due to factors like gene linkage, codominance, and incomplete dominance.'

A genetic cross between a red-flowered plant and a white-flowered plant produces pink-flowered offspring. This pattern, where the heterozygous phenotype is an intermediate blend of the two homozygous phenotypes, is an example of which deviation from Mendelian genetics?

A) Codominance

B) Incomplete dominance

C) Pleiotropy

D) Sex-linkage

Correct Answer: B

The content lists 'incomplete dominance' as a reason for traits not following Mendelian ratios. The scenario describes a blended or intermediate phenotype, which is the classic definition of incomplete dominance.

A trait is determined by a gene located on the X chromosome. Which of the following would be a key characteristic of this trait's inheritance?

A) It would be passed down exclusively through maternal inheritance from the mitochondria.

B) It would be an example of non-nuclear inheritance.

C) It would show distinct patterns of inheritance related to the sex of the individual.

D) It would affect multiple, unrelated traits simultaneously.

Correct Answer: C

According to the provided text, 'Sex-linked traits are determined by genes on sex chromosomes and show distinct patterns of inheritance.' The X chromosome is a sex chromosome.

The phenomenon where a single gene is responsible for affecting multiple, seemingly unrelated phenotypic traits is known as:

A) Codominance

B) Gene linkage

C) Non-nuclear inheritance

D) Pleiotropy

Correct Answer: D

The provided text defines this concept directly: 'Pleiotropy occurs when a single gene affects multiple traits...'

A scientist discovers that a specific type of metabolic disorder in an animal is passed down to all offspring only from the maternal parent. This inheritance pattern is best explained by:

A) Sex-linked inheritance on the X chromosome

B) Pleiotropy

C) Non-nuclear inheritance

D) Codominance

Correct Answer: C

The content explains that 'Some traits result from non-nuclear inheritance, where genes in mitochondria and chloroplasts are passed to offspring, typically through maternal inheritance.' Metabolic functions are heavily tied to mitochondria.

A genetic condition caused by a single gene mutation results in defects in the heart, bones, and eyes. How does this challenge the simple Mendelian model of inheritance?

A) It demonstrates codominance, where both alleles are expressed equally.

B) It is an example of pleiotropy, where one gene influences multiple traits.

C) It shows non-nuclear inheritance, as the gene must be in the mitochondria.

D) It is a sex-linked trait, showing different patterns in males and females.

Correct Answer: B

This scenario describes a single gene affecting multiple traits (heart, bones, eyes), which is the definition of pleiotropy provided in the text. Pleiotropy is listed as a deviation from Mendel's model.

In a particular species of cattle, a cross between a red-coated individual and a white-coated individual produces offspring that have both red and white hairs, creating a roan pattern. This is an example of which non-Mendelian inheritance pattern?

A) Pleiotropy

B) Incomplete dominance

C) Codominance

D) Maternal inheritance

Correct Answer: C

The content lists 'codominance' as a deviation from Mendel's model. The scenario describes a situation where both parental traits (red and white) are expressed simultaneously and distinctly in the offspring, which is the definition of codominance.

How does pleiotropy lead to deviations from Mendel's model?

A) It involves genes located on sex chromosomes, leading to different ratios in males and females.

B) It results from genes in mitochondria being passed down from the mother.

C) It causes a single gene to influence multiple traits, preventing them from segregating independently.

D) It creates a blended phenotype in heterozygotes due to incomplete dominance.

Correct Answer: C

The provided content explicitly states, 'Pleiotropy occurs when a single gene affects multiple traits, causing them not to segregate independently,' which is a deviation from Mendel's Law of Independent Assortment.

A researcher observes that certain traits in a eukaryotic organism are inherited exclusively from the female parent. This observation strongly suggests that the genes for these traits are located in which of the following?

A) The Y chromosome

B) The X chromosome

C) Autosomal chromosomes

D) Mitochondria or chloroplasts

Correct Answer: D

The content specifies that 'genes in mitochondria and chloroplasts are passed to offspring, typically through maternal inheritance.' This is the only option that explains exclusive inheritance from the female parent.

All of the following are examples of deviations from Mendel's model of inheritance mentioned in the text EXCEPT:

A) A single gene affecting multiple traits.

B) Traits determined by genes on sex chromosomes.

C) Inheritance of genes located in chloroplasts.

D) A trait determined by a single gene with a dominant and recessive allele.

Correct Answer: D

The content lists pleiotropy (A), sex-linked traits (B), and non-nuclear inheritance (C) as deviations. A trait determined by a single gene with a dominant and recessive allele is the basis of Mendel's original model, not a deviation from it.

The inheritance of genes located in mitochondria and chloroplasts is referred to as:

A) Pleiotropy

B) Non-nuclear inheritance

C) Sex-linked inheritance

D) Codominance

Correct Answer: B

The provided text directly states, 'Some traits result from non-nuclear inheritance, where genes in mitochondria and chloroplasts are passed to offspring...'