Genetics Practice Questions
NECO (Nigeria) · NECO Biology · 145 free MCQs with instant results and detailed explanations.
145
Total
31
Easy
82
Medium
32
Hard
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Sample Questions from Genetics
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Q1
Easy
What is the basic unit of heredity in living organisms?
A.
Gene
B.
Chromosome
C.
DNA
D.
Allele
Show Answer & Explanation
Correct Answer: A
A gene is the fundamental unit of heredity that carries the information for traits passed from parents to offspring. It is composed of DNA and is responsible for the expression of specific characteristics.
Q2
Easy
What is the basic unit of heredity in living organisms?
A.
Chromosome
B.
Gene
C.
DNA
D.
RNA
Show Answer & Explanation
Correct Answer: B
A gene is the fundamental unit of heredity that carries genetic information and determines specific traits in an organism.
Q3
Easy
If a trait in pea plants is controlled by a single gene with two alleles, where one allele is dominant (A) and the other is recessive (a), what will be the phenotype ratio of a heterozygous cross (Aa x Aa)?
A.
1:2:1
B.
3:1
C.
1:1
D.
9:3:3:1
Show Answer & Explanation
Correct Answer: B
The phenotype ratio from a heterozygous cross (Aa x Aa) will result in 3 dominant phenotypes (AA and Aa) to 1 recessive phenotype (aa), leading to a 3:1 ratio.
Q4
Medium
What is the expected phenotypic ratio of offspring in a monohybrid cross between two heterozygous parents?
A.
3:1
B.
1:2:1
C.
9:3:3:1
D.
1:1
Show Answer & Explanation
Correct Answer: A
In a monohybrid cross (Aa x Aa), the expected phenotypic ratio of dominant to recessive traits is 3:1. This is derived from the Punnett square showing that three offspring will express the dominant trait for every one that expresses the recessive trait.
Q5
Medium
If a pea plant with genotype Tt is crossed with a plant of genotype tt, what proportion of the offspring will likely show the dominant phenotype?
A.
50%
B.
75%
C.
100%
D.
25%
Show Answer & Explanation
Correct Answer: A
In this cross (Tt x tt), half of the offspring will have the genotype Tt (dominant phenotype) and the other half will be tt (recessive phenotype), resulting in a 50% expression of the dominant phenotype.
Q6
Medium
In a dihybrid cross between two heterozygous parents (RrYy), what is the expected genotypic ratio of the offspring?
A.
1:2:1
B.
9:3:3:1
C.
3:1:3:1
D.
1:1:1:1
Show Answer & Explanation
Correct Answer: B
In a dihybrid cross (RrYy x RrYy), the expected genotypic ratio is 9:3:3:1. This ratio reflects the combinations of the two traits being inherited independently according to the law of independent assortment.
Q7
Medium
If a mutation occurs in a gene that leads to a change in a protein's amino acid sequence, what type of mutation is this most likely to be?
A.
Silent mutation
B.
Missense mutation
C.
Nonsense mutation
D.
Frameshift mutation
Show Answer & Explanation
Correct Answer: B
A missense mutation results in a change in one amino acid in the protein sequence due to a substitution in the DNA sequence, which can affect the function of the protein depending on the nature of the change.
Q8
Hard
If a mother has a genotype of X^hX^H and the father has X^HY, what is the probability that they will have a son with hemophilia?
A.
50%
B.
25%
C.
75%
D.
0%
Show Answer & Explanation
Correct Answer: A
Hemophilia is an X-linked recessive disorder. The mother (X^hX^H) can pass either X^h (hemophilia) or X^H (normal) to her son, while the father (X^HY) can only provide his Y chromosome. The son will inherit X^h from his mother with a 50% chance, resulting in a 50% probability of having hemophilia.
Q9
Hard
In a certain plant species, flower color is controlled by two alleles: R (red) and r (white), with R being dominant over r. If a homozygous red flower (RR) is crossed with a heterozygous red flower (Rr), what will be the phenotypic ratio of the offspring?
A.
1 red : 1 white
B.
3 red : 1 white
C.
2 red : 1 white
D.
4 red : 0 white
Show Answer & Explanation
Correct Answer: D
The cross between RR (homozygous red) and Rr (heterozygous red) produces all offspring that are either RR or Rr, resulting in 100% red flowers. Hence, the ratio is 4 red : 0 white.
Q10
Hard
A geneticist conducts a test cross involving a pea plant showing dominant traits for height (T) and pod shape (S). The plant is TtSs (tall and smooth). What will be the expected phenotypic ratios in the offspring if this plant is crossed with ttss (short and wrinkled)?
A.
1 tall smooth : 1 short smooth
B.
1 tall smooth : 1 tall wrinkled : 1 short smooth : 1 short wrinkled
C.
1 tall smooth : 1 short wrinkled
D.
1 tall : 1 short : 1 smooth : 1 wrinkled
Show Answer & Explanation
Correct Answer: C
The cross TtSs x ttss yields offspring with phenotypes: TtSs (tall smooth) and ttss (short wrinkled), with a ratio of 1 tall smooth to 1 short wrinkled, as Tt and tt can produce only these combinations.
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Genetics — NECO (Nigeria) NECO Biology Practice Questions Online
This page contains 145 practice MCQs for the chapter Genetics in NECO (Nigeria) NECO Biology. The questions are organized by difficulty — 31 easy, 82 medium, 32 hard — so you can choose the right level for your preparation.
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