Genetics and Evolution Practice Questions
IB (International Baccalaureate) · IB Biology HL · 146 free MCQs with instant results and detailed explanations.
146
Total
47
Easy
75
Medium
24
Hard
Start Practicing Genetics and Evolution
Take a timed quiz or customize your practice session
Sample Questions from Genetics and Evolution
Here are 10 sample questions. Start a quiz to get randomized questions with scoring.
Q1
Easy
Which of the following best describes a homozygous individual?
A.
An individual with two identical alleles for a specific gene.
B.
An individual with two different alleles for a specific gene.
C.
An individual with three alleles for a specific gene.
D.
An individual with one dominant and one recessive allele.
Show Answer & Explanation
Correct Answer: A
A homozygous individual possesses two identical alleles for a specific gene, which means both alleles are the same, either both dominant or both recessive.
Q2
Easy
In a dihybrid cross between two heterozygous pea plants (RrYy), what is the expected phenotypic ratio of the offspring?
A.
9:3:3:1
B.
3:1
C.
1:2:1
D.
1:1
Show Answer & Explanation
Correct Answer: A
The expected phenotypic ratio from a dihybrid cross of two heterozygous individuals is 9:3:3:1, representing the combinations of two traits.
Q3
Easy
What is the significance of mutations in the process of evolution?
A.
Mutations are harmful and do not contribute to evolution.
B.
Mutations introduce genetic variation, which can lead to new traits.
C.
Mutations occur randomly and have no effect on evolution.
D.
Mutations only affect individuals and not populations.
Show Answer & Explanation
Correct Answer: B
Mutations introduce genetic variation in a population, providing the raw material for natural selection and potentially leading to new traits that can enhance survival and reproduction.
Q4
Medium
Which of the following best describes the role of ribosomes in protein synthesis?
A.
They synthesize mRNA from DNA.
B.
They translate mRNA into polypeptides.
C.
They modify proteins after synthesis.
D.
They transport amino acids to the nucleus.
Show Answer & Explanation
Correct Answer: B
Ribosomes are the cellular structures responsible for translating mRNA into polypeptides, thereby playing a crucial role in protein synthesis.
Q5
Medium
In humans, the allele for brown eyes (B) is dominant over the allele for blue eyes (b). What is the probability of a child having blue eyes if both parents are heterozygous for eye color?
A.
25%
B.
50%
C.
75%
D.
0%
Show Answer & Explanation
Correct Answer: A
When both parents are heterozygous (Bb), the Punnett square shows a 1:2:1 ratio of genotypes, resulting in a 25% probability of the child being homozygous recessive (bb) and thus having blue eyes.
Q6
Medium
Which of the following statements about mutations is true?
A.
All mutations are harmful to the organism.
B.
Mutations can only occur in germ cells.
C.
Some mutations can lead to beneficial traits.
D.
Mutations always result in visible changes in phenotype.
Show Answer & Explanation
Correct Answer: C
Some mutations can confer advantageous traits that enhance survival or reproduction, thereby playing a significant role in evolution.
Q7
Medium
If a population of rabbits has a gene frequency of 0.6 for a dominant allele (A) and 0.4 for its recessive counterpart (a), what is the expected frequency of the homozygous recessive genotype (aa) according to Hardy-Weinberg equilibrium?
A.
0.16
B.
0.24
C.
0.36
D.
0.04
Show Answer & Explanation
Correct Answer: A
According to Hardy-Weinberg equilibrium, the frequency of the homozygous recessive genotype (aa) can be calculated as q^2, where q is the frequency of the recessive allele (0.4). Therefore, 0.4 * 0.4 = 0.16.
Q8
Hard
In a population of rabbits, the allele for black fur (B) is dominant over the allele for white fur (b). If a heterozygous black rabbit (Bb) is crossed with a homozygous white rabbit (bb), what proportion of the offspring will have black fur?
A.
25%
B.
50%
C.
75%
D.
100%
Show Answer & Explanation
Correct Answer: B
When Bb (black) is crossed with bb (white), the offspring genotypes will be Bb (black) and bb (white) in a 1:1 ratio. Therefore, 50% of the offspring will have black fur.
Q9
Hard
In a certain plant species, flower color is determined by a single gene with two alleles: R (red) and r (white). If a true-breeding red-flowered plant is crossed with a heterozygous red-flowered plant, what is the expected phenotypic ratio of the offspring?
A.
1 red: 1 white
B.
3 red: 1 white
C.
1 red: 2 red: 1 white
D.
2 red: 1 white
Show Answer & Explanation
Correct Answer: A
The cross is RR (true-breeding red) with Rr (heterozygous red). The offspring would be 50% RR (red) and 50% Rr (red), resulting in a phenotypic ratio of 1 red: 1 white.
Q10
Hard
A population of rabbits is studied where fur color is controlled by two alleles: B (brown) and b (white). If the frequency of allele B is 0.7 and allele b is 0.3, what is the expected frequency of the homozygous recessive phenotype (bb) in this population according to Hardy-Weinberg equilibrium?
A.
0.09
B.
0.21
C.
0.30
D.
0.49
Show Answer & Explanation
Correct Answer: A
According to the Hardy-Weinberg principle, the frequency of the homozygous recessive phenotype (bb) is calculated as q^2, where q is the frequency of allele b. Here, q = 0.3, so q^2 = 0.3^2 = 0.09.
Showing 10 of 146 questions. Start a quiz to practice all questions with scoring and timer.
Practice All 146 Questions →Other IB (International Baccalaureate) Subjects
Genetics and Evolution — IB (International Baccalaureate) IB Biology HL Practice Questions Online
This page contains 146 practice MCQs for the chapter Genetics and Evolution in IB (International Baccalaureate) IB Biology HL. The questions are organized by difficulty — 47 easy, 75 medium, 24 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.