Genetic Information Variation and Relationships Practice Questions
A-Levels · A-Level Biology · 147 free MCQs with instant results and detailed explanations.
147
Total
46
Easy
73
Medium
28
Hard
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Sample Questions from Genetic Information Variation and Relationships
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Q1
Easy
What is the basic unit of heredity that consists of DNA and determines traits in an organism?
A.
Gene
B.
Chromosome
C.
Allele
D.
RNA
Show Answer & Explanation
Correct Answer: A
A gene is the basic unit of heredity made up of DNA. It carries the information required to produce specific traits in an organism, distinguishing it from chromosomes which are structures that contain many genes.
Q2
Easy
In a dihybrid cross between two heterozygous plants (RrYy), what is the expected phenotypic ratio of the offspring?
A.
3:1
B.
9:3:3:1
C.
1:2:1
D.
1:1:1:1
Show Answer & Explanation
Correct Answer: B
The expected phenotypic ratio for a dihybrid cross of two heterozygous parents (RrYy) is 9:3:3:1. This ratio represents the combinations of two traits in the offspring.
Q3
Easy
Which process involves the exchange of genetic material between homologous chromosomes during meiosis?
A.
Mutation
B.
Transcription
C.
Crossing over
D.
Replication
Show Answer & Explanation
Correct Answer: C
Crossing over is the process that occurs during meiosis where homologous chromosomes exchange segments of genetic material. This increases genetic variation in gametes.
Q4
Medium
Which of the following processes leads to genetic variation during meiosis?
A.
Independent assortment
B.
Transcription
C.
Replication
D.
Translation
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Correct Answer: A
Independent assortment occurs during meiosis when homologous chromosomes are segregated randomly into gametes, leading to genetic variation among offspring.
Q5
Medium
In a certain organism, the trait for flower color is determined by two alleles: R (red) and r (white). If a heterozygous plant (Rr) is crossed with a homozygous recessive plant (rr), what is the expected phenotypic ratio of the offspring?
A.
1:1
B.
3:1
C.
2:1
D.
1:2:1
Show Answer & Explanation
Correct Answer: A
The cross Rr x rr produces offspring with a 1:1 phenotypic ratio: 50% red (Rr) and 50% white (rr).
Q6
Medium
Which type of mutation is defined as a change in a single nucleotide base in DNA?
A.
Frameshift mutation
B.
Missense mutation
C.
Point mutation
D.
Deletion mutation
Show Answer & Explanation
Correct Answer: C
A point mutation is a change in a single nucleotide base, which can lead to different types of genetic changes such as silent, missense, or nonsense mutations.
Q7
Medium
What is the primary function of the enzyme DNA polymerase during DNA replication?
A.
To unwind the DNA helix
B.
To synthesize new DNA strands
C.
To remove RNA primers
D.
To link Okazaki fragments
Show Answer & Explanation
Correct Answer: B
DNA polymerase's primary function is to synthesize new DNA strands by adding nucleotides complementary to the template strand during DNA replication.
Q8
Hard
In a certain species of plant, flower color is determined by a single gene with two alleles: R (red) and r (white). If a heterozygous plant (Rr) is crossed with a homozygous recessive 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 expected phenotypic ratio is 1 red (Rr) to 1 white (rr) because the heterozygous plant can produce two types of gametes, R and r, which when crossed with the homozygous recessive plant (rr) results in 50% Rr (red) and 50% rr (white).
Q9
Hard
A geneticist is studying a rare trait in a population of fruit flies. The trait is caused by a recessive allele. If the frequency of the dominant allele is 0.8, what is the expected frequency of individuals exhibiting the recessive phenotype in the population according to Hardy-Weinberg equilibrium?
A.
0.16
B.
0.04
C.
0.64
D.
0.8
Show Answer & Explanation
Correct Answer: B
To find the frequency of the recessive phenotype, use the formula q^2, where q is the frequency of the recessive allele. If p (frequency of the dominant allele) is 0.8, then q = 1 - p = 0.2. Therefore, q^2 = (0.2)^2 = 0.04, which indicates the expected frequency of the recessive phenotype.
Q10
Hard
Which of the following best describes the role of DNA methylation in gene regulation?
A.
It promotes gene transcription by loosening chromatin structure.
B.
It inhibits gene transcription by adding methyl groups to cytosines in DNA.
C.
It enhances mRNA degradation, leading to reduced gene expression.
D.
It facilitates the binding of transcription factors to DNA.
Show Answer & Explanation
Correct Answer: B
DNA methylation typically inhibits gene transcription by adding methyl groups to cytosines in promoter regions, making the DNA less accessible for the transcription machinery.
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Practice All 147 Questions →Genetic Information Variation and Relationships — A-Levels A-Level Biology Practice Questions Online
This page contains 147 practice MCQs for the chapter Genetic Information Variation and Relationships in A-Levels A-Level Biology. The questions are organized by difficulty — 46 easy, 73 medium, 28 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.