Class 12 Biology · Chapter 6 · Test 3
Epistasis, Linkage, Crossing Over
42 MCQs
42 questions · 35 min · 42 marks
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Sample questions
The first 5 of 42. Try each one, then tap to see the answer.
Question 1
A cross between two plants with genotypes AaBb and AaBb results in an F1 generation that is 25% AABB, 50% AaBb and 25% aabb. Which reason most likely explains why other possible genotypes are not present?
- AThe genes underwent independent assortment
- BThe loci of the genes are close together.
- CThe loci of the genes are on different chromosomes.
- DCrossing over occurred between chromosomes.
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Answer: B
Only parental combinations appear, which shows the genes are closely linked.
Question 2
When the activity of one gene is suppressed by the activity of a non-allelic gene it is known as:
- AIncomplete dominance
- BEpistasis
- CComplete dominance
- DMultiple allelic effect
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Answer: B
Epistasis is the interaction in which an allele masks the effect of alleles at other loci.
Question 3
Polygenic characters are controlled by:
- AA single gene pair
- BMany gene pairs
- CSex chromosomes only
- DMitochondria
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Answer: B
All alleles of many genes contribute additively to the same trait.
Question 4
Polygenic traits show:
- ADiscontinuous variation
- BContinuous variation
- CNo variation
- DOnly two phenotypes
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Answer: B
They show a continuous range of differences in a population.
Question 5
Which of the following is a polygenic trait in humans?
- AABO blood group
- BSkin colour
- CHaemophilia
- DColour blindness
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Answer: B
Height, skin colour, weight and intelligence are polygenic.
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