Principles of Inheritance Quiz - CBSE Class 12 Biology

Free practice quiz: Principles of Inheritance (CBSE Class 12 Biology). 20 multiple-choice questions with answers and explanations. Play online, no sign-up needed.

Sample questions

1. What is the phenotypic ratio of a monohybrid cross between two heterozygous individuals?

   1. 1:1
   2. 3:1
   3. 1:2:1
   4. 9:3:3:1
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   Answer: B. 3:1

   A monohybrid cross between two heterozygotes (e.g., Aa x Aa) results in a 3:1 phenotypic ratio of dominant to recessive traits.

2. What is codominance?

   1. When one allele masks another.
   2. When both alleles are expressed equally in the heterozygote.
   3. When the heterozygote shows an intermediate phenotype.
   4. When there are multiple alleles for a single gene.
   Show answer

   Answer: B. When both alleles are expressed equally in the heterozygote.

   Codominance is a type of inheritance where both alleles are fully expressed in the heterozygote, unlike incomplete dominance where the heterozygote displays an intermediate phenotype.

3. In a dihybrid cross between two heterozygotes (AaBb x AaBb), what is the probability of obtaining an offspring with the genotype AABB?

   1. 1/2
   2. 1/4
   3. 1/8
   4. 1/16
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   Answer: D. 1/16

   The probability of inheriting AA from both parents is 1/4 (1/2 x 1/2), and the probability of inheriting BB from both parents is also 1/4 (1/2 x 1/2). Therefore, the probability of obtaining AABB is (1/4) x (1/4) = 1/16.

4. In a cross involving two genes, what is the expected phenotypic ratio in the F2 generation if the two genes show complete linkage?

   1. 9:3:3:1
   2. 1:1:1:1
   3. 3:1
   4. The ratio will depend on the parental genotypes.
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   Answer: C. 3:1

   Complete linkage means the genes are located very close together on the same chromosome and do not recombine during meiosis. Therefore, the phenotypic ratio will resemble that of a monohybrid cross.

5. How does the environment interact with genotype to influence phenotype?

   1. The environment has no influence on phenotype.
   2. The environment completely determines the phenotype, ignoring the genotype.
   3. The environment can modify or mask the expression of a genotype.
   4. The genotype and environment are completely independent.
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   Answer: C. The environment can modify or mask the expression of a genotype.

   The environment can interact with the genotype to influence the phenotype. Environmental factors can affect gene expression, resulting in variations in phenotypic expression, even among individuals with the same genotype.

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