Genetics Practice Questions
HSC/SSC (Bangladesh) · HSC Biology · 140 free MCQs with instant results and detailed explanations.
140
Total
36
Easy
75
Medium
29
Hard
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Sample Questions from Genetics
Here are 10 sample questions. Start a quiz to get randomized questions with scoring.
Q1
Easy
In Mendelian genetics, what is the expected phenotypic ratio in the offspring of a monohybrid cross?
A.
3:1
B.
1:1
C.
9:3:3:1
D.
1:2:1
Show Answer & Explanation
Correct Answer: A
In a monohybrid cross, where one trait is examined, the expected phenotypic ratio of the offspring is 3:1, indicating that three offspring exhibit the dominant trait for every one that exhibits the recessive trait.
Q2
Easy
If a pea plant has a genotype of Tt for tallness (T) and shortness (t), what is the probability that it will produce a gamete with the t allele?
A.
50%
B.
25%
C.
75%
D.
100%
Show Answer & Explanation
Correct Answer: A
In a heterozygous genotype like Tt, the plant can produce two types of gametes: T and t. The probability of producing a gamete with the t allele is 50%, as there is one t allele out of the two possible alleles.
Q3
Easy
In humans, brown eyes (B) are dominant over blue eyes (b). If a homozygous brown-eyed individual mates with a blue-eyed individual, what percentage of their offspring will have brown eyes?
A.
100%
B.
50%
C.
75%
D.
0%
Show Answer & Explanation
Correct Answer: A
When a homozygous brown-eyed individual (BB) mates with a blue-eyed individual (bb), all offspring will inherit one B allele and one b allele, resulting in 100% having brown eyes (Bb).
Q4
Medium
In a dihybrid cross between two heterozygous plants (YyRr), what is the phenotypic ratio of the offspring?
A.
9:3:3:1
B.
1:1:1:1
C.
3:1
D.
1:2:1
Show Answer & Explanation
Correct Answer: A
The phenotypic ratio of a dihybrid cross between two heterozygous individuals is 9:3:3:1. This ratio represents the four possible phenotypes resulting from the combination of traits.
Q5
Medium
In a certain species of fruit flies, the allele for red eyes (R) is dominant over the allele for white eyes (r). If a red-eyed male fly is crossed with a white-eyed female fly, which of the following percentages of the offspring will have red eyes if the male is heterozygous?
A.
25%
B.
50%
C.
75%
D.
100%
Show Answer & Explanation
Correct Answer: C
If the male fruit fly is heterozygous (Rr) and the female is homozygous recessive (rr), the offspring will have a 75% chance of having red eyes (RR or Rr) and a 25% chance of having white eyes (rr), resulting in 75% red-eyed offspring.
Q6
Medium
What is the expected phenotypic ratio in the offspring of a test cross between an unknown genotype and a homozygous recessive organism?
A.
3:1
B.
1:1
C.
1:2:1
D.
1:1:1:1
Show Answer & Explanation
Correct Answer: B
In a test cross, when an unknown genotype is crossed with a homozygous recessive organism, the expected phenotypic ratio in the offspring will be 1:1 for dominant to recessive traits.
Q7
Medium
If a mutation occurs in a gene involved in flower color in plants, how might this affect the offspring of the mutated plant?
A.
Offspring will always show the same flower color as the parent.
B.
Offspring may show a variation in flower color.
C.
All offspring will have no flower color.
D.
Offspring will be genetically identical to the mutated plant.
Show Answer & Explanation
Correct Answer: B
A mutation in a gene can lead to variations in traits such as flower color. Offspring may inherit the mutated allele, resulting in different flower colors compared to the parent.
Q8
Hard
In a certain species of pea plants, the allele for tall plants (T) is dominant over the allele for short plants (t). If two heterozygous tall plants are crossed, what is the probability of obtaining a short plant in the offspring?
A.
25%
B.
50%
C.
75%
D.
100%
Show Answer & Explanation
Correct Answer: A
When two heterozygous tall plants (Tt) are crossed, the possible combinations of alleles are TT, Tt, Tt, and tt. This results in a 1:2:1 ratio, meaning there is a 25% chance of producing a homozygous recessive short plant (tt).
Q9
Hard
In humans, the ability to roll one's tongue is dominant (R) over the inability to roll it (r). If a heterozygous tongue roller is crossed with a homozygous non-roller, what fraction of the offspring are expected to be able to roll their tongues?
A.
0%
B.
25%
C.
50%
D.
75%
Show Answer & Explanation
Correct Answer: C
Crossing a heterozygous tongue roller (Rr) with a homozygous non-roller (rr) results in offspring with genotypes of Rr and rr. The probability of offspring that can roll their tongues (Rr) is 50%, since only half of the combinations will have the dominant allele.
Q10
Hard
In a genetic cross between two heterozygous pea plants (Tt) for height, where T is tall and t is short, what is the probability of obtaining a short plant in the offspring?
A.
25%
B.
50%
C.
75%
D.
100%
Show Answer & Explanation
Correct Answer: A
The cross Tt x Tt results in a Punnett square showing TT, Tt, Tt, and tt, where tt represents the short phenotype. Thus, the probability of obtaining a short plant (tt) is 1 out of 4, or 25%.
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Genetics — HSC/SSC (Bangladesh) HSC Biology Practice Questions Online
This page contains 140 practice MCQs for the chapter Genetics in HSC/SSC (Bangladesh) HSC Biology. The questions are organized by difficulty — 36 easy, 75 medium, 29 hard — so you can choose the right level for your preparation.
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