Genetics Practice Questions
WAEC (West Africa) · WAEC Biology · 142 free MCQs with instant results and detailed explanations.
142
Total
38
Easy
75
Medium
29
Hard
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Sample Questions from Genetics
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Q1
Easy
In a monohybrid cross between two heterozygous parents (Bb x Bb), what is the expected phenotypic ratio of the offspring?
A.
3:1
B.
1:2:1
C.
2:1
D.
1:1
Show Answer & Explanation
Correct Answer: A
In a monohybrid cross involving two heterozygous parents, the expected phenotypic ratio of the offspring is 3:1. This means that there will be three offspring expressing the dominant trait for every one offspring expressing the recessive trait.
Q2
Easy
Which of the following statements about alleles is true?
A.
Alleles are different forms of a gene.
B.
Alleles can only be dominant.
C.
Alleles are found in the nucleus only.
D.
Alleles do not affect traits.
Show Answer & Explanation
Correct Answer: A
Alleles are different variants of the same gene that can produce variations in a trait. They can be dominant or recessive, and they are found in chromosomes, not just in the nucleus. Alleles directly influence the traits of an organism.
Q3
Easy
Which of the following is NOT a characteristic of Mendelian inheritance?
A.
Traits are controlled by single genes
B.
Genes segregate independently during gamete formation
C.
Traits can be influenced by multiple genes
D.
Some alleles can be dominant over others
Show Answer & Explanation
Correct Answer: C
Mendelian inheritance focuses on single genes and their dominant or recessive traits. The concept of traits being influenced by multiple genes pertains to polygenic inheritance, which is not a feature of Mendelian inheritance.
Q4
Medium
In human genetics, which of the following describes a trait that is influenced by multiple genes?
A.
Polygenic inheritance
B.
Monogenic inheritance
C.
Codominance
D.
Incomplete dominance
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Correct Answer: A
Polygenic inheritance refers to traits that are controlled by multiple genes, leading to a range of phenotypes. This is common in traits such as skin color and height.
Q5
Medium
A couple has two children, both of whom are boys. What is the probability that their next child will also be a boy, assuming the sex of the child is independent of previous births?
A.
1/2
B.
1/4
C.
1/3
D.
1/1
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Correct Answer: A
The probability of having a boy or a girl is always 1/2 for each child regardless of previous outcomes, as each birth is independent.
Q6
Medium
In a dihybrid cross of pea plants, what is the expected phenotypic ratio of the offspring for two traits governed by independent assortment?
A.
9:3:3:1
B.
3:1
C.
1:2:1
D.
1:1:1:1
Show Answer & Explanation
Correct Answer: A
The expected phenotypic ratio for a dihybrid cross, where two traits are independently assorted, is 9:3:3:1, reflecting the combinations of dominant and recessive traits.
Q7
Medium
Which of the following accurately describes the role of messenger RNA (mRNA) in protein synthesis?
A.
mRNA carries amino acids to the ribosome.
B.
mRNA transcribes DNA into RNA.
C.
mRNA carries the genetic code from DNA to the ribosome.
D.
mRNA catalyzes the formation of peptide bonds.
Show Answer & Explanation
Correct Answer: C
mRNA carries the genetic code transcribed from DNA to the ribosome, where it directs the synthesis of proteins based on that code.
Q8
Hard
In a certain plant species, the allele for tall plants (T) is dominant over the allele for short plants (t). If a homozygous tall plant is crossed with a heterozygous tall plant, what is the probability of obtaining a short plant in the offspring?
A.
25%
B.
0%
C.
50%
D.
75%
Show Answer & Explanation
Correct Answer: B
Since one parent is homozygous tall (TT) and the other is heterozygous tall (Tt), all offspring will inherit at least one dominant allele (T), resulting in only tall plants. Therefore, the probability of obtaining a short plant (tt) is 0%.
Q9
Hard
A certain trait in a population shows incomplete dominance. If a plant with red flowers (RR) is crossed with a plant with white flowers (WW), what color will the offspring predominantly display?
A.
Red
B.
White
C.
Pink
D.
Purple
Show Answer & Explanation
Correct Answer: C
In incomplete dominance, the heterozygous genotype (RW) results in a blending of traits. Therefore, the offspring from a red flower (RR) and white flower (WW) cross will predominantly display pink flowers (RW).
Q10
Hard
In a certain plant species, flower color is controlled by a single gene with two alleles: R (red) and r (white). If a homozygous red-flowered plant (RR) is crossed with a homozygous white-flowered plant (rr), what will be the expected phenotypic ratio of the offspring in the F1 generation?
A.
100% red flowers
B.
75% red and 25% white flowers
C.
50% red and 50% white flowers
D.
100% white flowers
Show Answer & Explanation
Correct Answer: A
The cross between RR (red) and rr (white) produces F1 offspring all having the genotype Rr. Since R is dominant over r, all F1 plants will exhibit the red flower phenotype, resulting in a 100% red flowers ratio.
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Genetics — WAEC (West Africa) WAEC Biology Practice Questions Online
This page contains 142 practice MCQs for the chapter Genetics in WAEC (West Africa) WAEC Biology. The questions are organized by difficulty — 38 easy, 75 medium, 29 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.