Unit 5: Heredity

AP Biology — 24 practice questions with detailed explanations. Use the links below to open each full question page (ideal for search indexing and deep study).

Unit summary

This unit covers core ideas tested on the AP exam. Each listed item links to a standalone page with the full stem, answer choices where applicable, a step-by-step explanation, and the correct answer. Difficulty labels help you prioritize review.

Questions in this unit

Genes A and B are located close to each other on the same chromosome. A heterozygous individual with the genotype A b / a B is crossed with a homozygous recessive individual. The observed offspring occur in a phenotypic ratio of approximately 40:10:10:40. What is the most likely explanation for this deviation from the expected 1:1:1:1 ratio?easy · mcq · 1 pt
Color blindness is an X-linked recessive trait. A color-blind male and a female with normal vision, whose father was color-blind, have a child. What is the probability that their first-born child will be a color-blind male?medium · mcq · 1 pt
During meiosis I, homologous chromosomes exchange segments of non-sister chromatids. Which of the following best describes the evolutionary significance of this process?medium · mcq · 1 pt
In Labrador retrievers, coat color is determined by two genes. The B gene controls pigment color (B = black, b = brown), while the E gene controls pigment deposition. If a dog is homozygous recessive for the E gene (ee), the coat is yellow regardless of the B gene's alleles. What is the genetic phenomenon described here?hard · mcq · 1 pt
Himalayan rabbits are homozygous for a mutation in the tyrosinase gene that causes temperature-sensitive pigment production. They develop black fur on their extremities (ears, nose, paws) where body temperature is lower, and white fur on their torso. What does this phenomenon best illustrate?hard · mcq · 1 pt
A biologist observes a human egg cell that contains two X chromosomes. During which of the following meiotic stages did nondisjunction most likely occur to produce this specific gamete?easy · mcq · 1 pt
In peas, round seeds (R) are dominant to wrinkled seeds (r), and yellow seeds (Y) are dominant to green seeds (y). Two plants with the genotype RrYy are crossed. What is the probability that a randomly selected offspring will have wrinkled, green seeds?hard · mcq · 1 pt
A diploid organism has a somatic chromosome number of 2n = 24. How many different combinations of maternal and paternal chromosomes can result in its gametes solely due to independent assortment during meiosis?hard · mcq · 1 pt
A geneticist is studying a trait that is caused by an autosomal dominant gene. If a woman with the dominant gene has a child with a man who has no copies of the dominant gene, what is the probability that the child will exhibit the dominant trait?easy · mcq · 1 pt
In a certain population, the genotype of an individual can be represented by the following Punnett square: | Rr | Rr || rR | rR |. What is the most likely genotype of the offspring from a cross between two heterozygous individuals?hard · mcq · 1 pt
The primary reason that Down syndrome is more common in individuals with Turner syndrome (45,X) ishard · mcq · 1 pt
Based on the data, which of the following would be the most likely outcome of crossing a plant with genotype RR (tall) with a plant with genotype rr (short)?medium · mcq · 1 pt
Which of the following statements best describes the primary reason for the increased rate of mutation observed in cancer cells?medium · mcq · 1 pt
In a certain population of pea plants, 3 out of 10 plants exhibit the tall trait, while the remaining 7 exhibit the short trait. This ratio reflectseasy · mcq · 1 pt
A geneticist is studying the inheritance of a trait in humans. She observes that two parents who are both carriers of a specific disease have offspring with a 75% chance of developing the disease. Which of the following is the most likely genotype of the affected offspring?hard · mcq · 1 pt
A geneticist is studying the inheritance of a trait in mice. He observes that the offspring of two parents who are homozygous recessive (gg) have a 25% chance of expressing the trait. Which of the following is the most likely genotype of the non-expressing offspring?medium · mcq · 1 pt
A geneticist is studying the inheritance of a trait in humans. She observes that two siblings who are both carriers of a specific disease have offspring with a 50% chance of developing the disease. Which of the following is the most likely genotype of the affected offspring?medium · mcq · 1 pt
A geneticist is studying the inheritance of a trait in plants. He observes that the offspring of two parents who are heterozygous for a specific gene (Tt) have a 1:1 ratio of T:tt. Which of the following is the most likely explanation for this ratio?hard · mcq · 1 pt
A geneticist is studying the inheritance of a trait in humans. She observes that two siblings who are both affected with a specific disease are more likely to have children with the disease than two siblings who are not affected. Which of the following is the most likely explanation for this observation?hard · mcq · 1 pt
A geneticist is studying the inheritance of a trait in yeast. She observes that the offspring of two parents who are homozygous dominant (CC) have a 75% chance of expressing the trait. Which of the following is the most likely genotype of the non-expressing offspring?hard · mcq · 1 pt
A researcher is studying the inheritance of a trait in mice. He observes that the offspring of two heterozygous parents (Mm) have a 3:1 ratio of M:Mm:m:Mm. Which of the following is the most likely explanation for this ratio?medium · mcq · 1 pt
A geneticist is studying the inheritance of a trait in humans. She observes that the offspring of two parents who are carriers of a recessive allele for a specific disease have a 25% chance of developing the disease. Which of the following is the most likely genotype of the affected offspring?medium · mcq · 1 pt
A geneticist is studying the inheritance of a trait in pea plants. He crosses a true-breeding purple-flowered plant with a true-breeding white-flowered plant and observes the following offspring: 100 purple-flowered, 100 white-flowered. Which of the following is the most likely ratio of genotypes in the offspring?easy · mcq · 1 pt
A population of plants has two alleles for a specific gene: R (red flowers) and r (white flowers). The frequency of the R allele is 0.6. What is the expected frequency of the rr genotype?easy · mcq · 1 pt

Sample prompts

Short previews of topics covered (not full question text).

Genes A and B are located close to each other on the same chromosome. A heterozy…
Color blindness is an X-linked recessive trait. A color-blind male and a female …
During meiosis I, homologous chromosomes exchange segments of non-sister chromat…
In Labrador retrievers, coat color is determined by two genes. The B gene contro…
Himalayan rabbits are homozygous for a mutation in the tyrosinase gene that caus…
A biologist observes a human egg cell that contains two X chromosomes. During wh…
In peas, round seeds (R) are dominant to wrinkled seeds (r), and yellow seeds (Y…
A diploid organism has a somatic chromosome number of 2n = 24. How many differen…
A geneticist is studying a trait that is caused by an autosomal dominant gene. I…
In a certain population, the genotype of an individual can be represented by the…
The primary reason that Down syndrome is more common in individuals with Turner …
Based on the data, which of the following would be the most likely outcome of cr…