Heredity Practice Questions
AP (Advanced Placement) · AP Biology · 148 free MCQs with instant results and detailed explanations.
148
Total
43
Easy
74
Medium
31
Hard
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Sample Questions from Heredity
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Q1
Easy
In a dihybrid cross between two heterozygous pea plants (RrYy), what fraction of the offspring will display the dominant phenotype for both traits?
A.
1/4
B.
3/4
C.
9/16
D.
1/16
Show Answer & Explanation
Correct Answer: C
In a dihybrid cross, the phenotypic ratio is 9:3:3:1. The fraction that shows both dominant traits (R_Y_) is 9 out of 16 total combinations.
Q2
Easy
If a trait in a population is influenced by multiple genes, what is the term used to describe this type of inheritance?
A.
Polygenic inheritance
B.
Monogenic inheritance
C.
Codominance
D.
Incomplete dominance
Show Answer & Explanation
Correct Answer: A
Polygenic inheritance refers to a trait that is controlled by multiple genes, leading to a wide range of phenotypes.
Q3
Easy
What is the probability of obtaining a homozygous recessive offspring from a cross between two heterozygous parents (Aa x Aa)?
A.
25%
B.
50%
C.
75%
D.
100%
Show Answer & Explanation
Correct Answer: A
The Punnett square shows that there is a 1 in 4 chance of offspring being homozygous recessive (aa), hence the probability is 25%.
Q4
Medium
What is the expected phenotypic ratio in the offspring of a monohybrid cross between two heterozygous parents (Aa x Aa)?
A.
3:1
B.
1:2:1
C.
1:1
D.
9:3:3:1
Show Answer & Explanation
Correct Answer: A
In a monohybrid cross (Aa x Aa), the expected phenotypic ratio of the offspring is 3:1, where 3 will show the dominant trait and 1 will show the recessive trait.
Q5
Medium
In a dihybrid cross between two organisms heterozygous for both traits (AaBb x AaBb), what is the probability of obtaining offspring with the genotype AABB?
A.
1/16
B.
1/8
C.
1/4
D.
3/16
Show Answer & Explanation
Correct Answer: A
The probability of obtaining the genotype AABB in a dihybrid cross (AaBb x AaBb) is 1/16, as you can calculate the individual probabilities for each trait and then multiply them.
Q6
Medium
If two genes are located on the same chromosome, what is the term used to describe their inheritance pattern?
A.
Independent assortment
B.
Linked inheritance
C.
Codominance
D.
Incomplete dominance
Show Answer & Explanation
Correct Answer: B
When two genes are located on the same chromosome, they tend to be inherited together, which is known as linked inheritance.
Q7
Medium
Which of the following statements about sex-linked traits is true?
A.
They are always recessive.
B.
They can be dominant or recessive.
C.
They are found only on the Y chromosome.
D.
They are never expressed in females.
Show Answer & Explanation
Correct Answer: B
Sex-linked traits can be either dominant or recessive, depending on the specific trait and its location on the X or Y chromosome.
Q8
Hard
In a cross between two organisms, one homozygous dominant for a trait and one homozygous recessive, what is the expected phenotypic ratio of the F1 generation?
A.
1:0
B.
3:1
C.
1:2:1
D.
0:1
Show Answer & Explanation
Correct Answer: A
In a cross between a homozygous dominant (AA) and a homozygous recessive (aa) organism, all individuals in the F1 generation will be heterozygous (Aa), resulting in a phenotype that displays the dominant trait, leading to a phenotypic ratio of 1:0.
Q9
Hard
A certain trait in pea plants is governed by a single gene with two alleles, where 'R' is dominant over 'r'. If a plant heterozygous for this trait (Rr) is self-fertilized, what is the probability that an offspring will be homozygous recessive?
A.
25%
B.
50%
C.
75%
D.
0%
Show Answer & Explanation
Correct Answer: A
When a heterozygous plant (Rr) is self-fertilized, the possible gametes are R and r. The Punnett square shows that the combination of r from each parent gives a homozygous recessive offspring (rr) in 1 out of 4 possibilities, leading to a 25% probability.
Q10
Hard
In a certain plant species, flower color is determined by two alleles: R (red) and r (white). If a plant heterozygous for flower color (Rr) is crossed with a homozygous white plant (rr), what is the expected phenotypic ratio of the offspring?
A.
1 red: 1 white
B.
3 red: 1 white
C.
1 red: 2 white
D.
All red
Show Answer & Explanation
Correct Answer: A
The cross Rr x rr results in two possible genotypes: Rr (red) and rr (white). Therefore, the expected phenotypic ratio is 1 red to 1 white.
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Heredity — AP (Advanced Placement) AP Biology Practice Questions Online
This page contains 148 practice MCQs for the chapter Heredity in AP (Advanced Placement) AP Biology. The questions are organized by difficulty — 43 easy, 74 medium, 31 hard — so you can choose the right level for your preparation.
Every question includes a detailed explanation to help you understand the concept, not just memorize answers. Take a timed quiz to simulate exam conditions, or practice at your own pace with no time limit.