Genetics and Heredity Practice Questions
Thanaweya Amma (Egypt) · Thanaweya Biology · 147 free MCQs with instant results and detailed explanations.
147
Total
36
Easy
79
Medium
32
Hard
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Sample Questions from Genetics and Heredity
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Q1
Easy
In a monohybrid cross between two heterozygous individuals (Aa x Aa), what is the expected phenotypic ratio of the offspring?
A.
1:2:1
B.
3:1
C.
9:3:3:1
D.
1:1
Show Answer & Explanation
Correct Answer: B
In a monohybrid cross (Aa x Aa), the expected phenotypic ratio of the offspring is 3:1, where 3 show the dominant trait and 1 shows the recessive trait.
Q2
Easy
Which of the following is an example of a sex-linked trait in humans?
A.
Eye color
B.
Hemophilia
C.
Blood type
D.
Height
Show Answer & Explanation
Correct Answer: B
Hemophilia is a sex-linked trait that is carried on the X chromosome, making it more likely to affect males who have only one X chromosome.
Q3
Easy
What is the basic unit of heredity that transmits traits from parents to offspring?
A.
Gene
B.
Chromosome
C.
DNA
D.
RNA
Show Answer & Explanation
Correct Answer: A
A gene is the fundamental unit of heredity and is responsible for the transmission of traits from parents to their offspring. Chromosomes are structures that contain genes, while DNA is the molecular basis of genes.
Q4
Medium
In the context of human genetics, if both parents are carriers of a recessive allele for cystic fibrosis (CF), what is the probability that their child will have the disease?
A.
25%
B.
50%
C.
75%
D.
100%
Show Answer & Explanation
Correct Answer: A
When both parents are carriers of a recessive trait (CF), there is a 25% chance (1 in 4) that the child will inherit two recessive alleles and express the disease.
Q5
Medium
Which of the following best describes the role of messenger RNA (mRNA) in protein synthesis?
A.
It carries amino acids to the ribosome.
B.
It transports genetic information from DNA to the ribosome.
C.
It forms the structural component of ribosomes.
D.
It provides energy for protein synthesis.
Show Answer & Explanation
Correct Answer: B
mRNA serves as a template that carries the genetic information from DNA in the nucleus to the ribosomes in the cytoplasm, where proteins are synthesized.
Q6
Medium
If a mutation occurs in a somatic cell, how can it affect the offspring of that organism?
A.
It will always be inherited by the offspring.
B.
It will never be inherited by the offspring.
C.
It may be inherited if it occurs in the germline cells.
D.
It can only affect the phenotype of the organism, not inheritance.
Show Answer & Explanation
Correct Answer: B
Mutations in somatic cells are not passed on to offspring because these mutations occur in non-reproductive cells and do not affect the germline DNA.
Q7
Medium
In a dihybrid cross of two pea plants where one trait is seed color (yellow is dominant to green) and the other is seed shape (round is dominant to wrinkled), what phenotype ratio can be expected in the offspring?
A.
9:3:3:1
B.
3:1
C.
1:2:1
D.
1:1:1:1
Show Answer & Explanation
Correct Answer: A
In a dihybrid cross, the expected phenotypic ratio for two traits is 9:3:3:1, indicating the combination of dominant and recessive traits in the offspring.
Q8
Hard
A genetic cross between a homozygous tall pea plant (TT) and a homozygous short pea plant (tt) results in offspring. What is the expected phenotypic ratio of the offspring?
A.
1 Tall: 1 Short
B.
All Tall
C.
3 Tall: 1 Short
D.
1 Tall: 2 Short
Show Answer & Explanation
Correct Answer: B
All offspring from this cross will inherit one dominant allele (T) from the tall parent and one recessive allele (t) from the short parent, resulting in a genotype of Tt, which expresses the tall phenotype. Therefore, all the offspring will be tall.
Q9
Hard
In a particular species of fruit flies, the trait for red eyes (R) is dominant over the trait for white eyes (r). If a heterozygous red-eyed male (Rr) is crossed with a white-eyed female (rr), what is the probability of obtaining a red-eyed offspring?
A.
0%
B.
25%
C.
50%
D.
75%
Show Answer & Explanation
Correct Answer: C
The cross Rr (red-eyed male) with rr (white-eyed female) yields offspring genotypes of Rr and rr. The Rr offspring exhibit red eyes while rr exhibit white eyes. Therefore, there is a 50% probability of producing red-eyed offspring.
Q10
Hard
In a certain plant species, leaf shape is controlled by two alleles: A (round) is dominant over a (pointed). If a homozygous round-leaved plant is crossed with a heterozygous round-leaved plant, what is the expected phenotypic ratio of their offspring?
A.
3 round : 1 pointed
B.
1 round : 1 pointed
C.
1 round : 2 round : 1 pointed
D.
4 round : 0 pointed
Show Answer & Explanation
Correct Answer: D
The homozygous round plant (AA) crossed with a heterozygous round plant (Aa) will produce offspring with genotypes AA and Aa, resulting in all round-leaved plants (100% round).
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Genetics and Heredity — Thanaweya Amma (Egypt) Thanaweya Biology Practice Questions Online
This page contains 147 practice MCQs for the chapter Genetics and Heredity in Thanaweya Amma (Egypt) Thanaweya Biology. The questions are organized by difficulty — 36 easy, 79 medium, 32 hard — so you can choose the right level for your preparation.
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