Biology Questions and Answers – Inheritance Principles – Incomplete Dominance

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This set of Biology Multiple Choice Questions & Answers (MCQs) focuses on “Inheritance Principles – Incomplete Dominance”.

1. Which of the following shows incomplete dominance?
a) Flower color in garden peas
b) Flower color in snapdragon
c) Blood grouping in humans
d) Pod color in garden peas
View Answer

Answer: b
Explanation: The garden peas exhibit Mendelian inheritance. Human blood grouping shows codominance. Snapdragon flower color shows incomplete dominance.
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2. Incomplete dominance violated Mendel’s law of dominance.
a) True
b) False
View Answer

Answer: b
Explanation: The law of dominance still holds. Incomplete dominance also involves a pair of factors that encode for a specific phenotype. However, the dominance of one over the other is incomplete, giving rise to a blending of phenotypes in heterozygotes.

3. If a cross between true-breeding red-flowered and true-breeding white-flowered plants give rise to pink-flowered progeny, what is the mode of inheritance?
a) Complete dominance
b) Incomplete dominance
c) Codominance
d) Multiple allelism
View Answer

Answer: b
Explanation: Incomplete dominance involves the blending of characters in the progeny that are heterozygotes. Here red and white-flowered plants produce pink-flowered progeny. Hence this is an instance of incomplete dominance.
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4. Rahul observed a plant in his garden. He hypothesized that the stem height exhibited incomplete dominance. To check for his, he created true-breeding lines of tall and short plants. He then crossed these and sampled 1000 progeny. Which of the following cases, matches his hypothesis?
a) 500 tall plants, 250 intermediate plants, and 250 small plants
b) 250 tall plants, 500 intermediate plants, and 250 small plants
c) 250 tall plants, 250 intermediate plants, and 500 small plants
d) 125 tall plants, 750 intermediate plants, and 125 small plants
View Answer

Answer: b
Explanation: The phenotypic ratio of the progeny that exhibits incomplete dominance is 1:2:1. Therefore, of 1000 plants sampled from the progeny, 250 should be tall, 250 should be small, and 500 intermediate plants if incomplete dominance holds.

5. The genotypic ratio observed in incomplete dominance is different from the genotypic ratio observed in complete dominance.
a) True
b) False
View Answer

Answer: b
Explanation: Complete dominance refers to the Mendelian pattern of inheritance. Both incomplete and complete dominance produce offsprings that have the same genotypic ratios. The two processes differ in the phenotypic ratios.
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6. In the case of incomplete dominance, which zygosity expresses the blending of characters?
a) Homozygosity
b) Heterozygosity
c) Hemizgosity
d) Nullizygosity
View Answer

Answer: b
Explanation: The blending of characters is the characteristic feature of incomplete dominance. This requires the presence of two factors in the organism. Hence it occurs only in the heterozygous state.

7. What holds the information for a particular trait?
a) Gene
b) Genome
c) Exon
d) Intron
View Answer

Answer: a
Explanation: The factors hypothesized by Mendel encode for traits that are expressed. These are now called genes. Genes are fragments of DNA that code for a functional protein. In eukaryotes, genes are composed of two elements namely, exons and introns. Exons code for an mRNA transcript, while the introns are non-coding elements and are removed out by a spliceosomal complex.
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8. Which of the following fill not be the nature of enzyme encoded by a recessive gene?
a) Less efficient enzyme
b) No function observed for the enzyme
c) Abnormal function of the enzyme
d) More efficient enzyme
View Answer

Answer: d
Explanation: Recessive alleles lose the capability to encode because of the presence of a better functioning allele. Hence a more efficient enzyme is highly unlikely to be encoded by a recessive gene.

9. The flower color in Snapdragon exhibits _______
a) complete dominance
b) incomplete dominance
c) codominance
d) multiple allelism
View Answer

Answer: b
Explanation: The Snapdragon produces pink flowers after the mating of red-flowered and white-flowered plants. Thus, there is a blending of characters. This is called incomplete dominance.
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