# Class 12 Biology MCQ – Inheritance Principles – Punnett Square-1

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This set of Class 12 Biology Chapter 5 Multiple Choice Questions & Answers (MCQs) focuses on “Inheritance Principles – Punnett Square-1”.

1. What diagram is used to study the production of zygotes in F1 and F2 generation?
a) Punnett square
b) Punnett rectangle
c) Punnett rhombus
d) Punnett circle

Explanation: The Punnett square is a mathematical tool used in probability and statistics. Mendel employed it to study the genotypes of F1 and F2 progeny based on the games produced by the previous generation.

2. Who deserves the credit to discover Punnett square?
a) Reginald Punnett
b) Gregor Mendel
c) John Watson
d) Maurice Punnett

Explanation: The Punnett square was discovered by a British scientist named Reginald Punnett. Its importance was recognized by Gregor Mendel, who used it to study the patterns of inheritance and thus formulate the laws of inheritance.

3. Where are the parental genotypes mentioned in a Punnett square?
a) Left column and top row
b) Left column and right column
c) Top row and bottom row
d) Right column and bottom row

Explanation: Punnett square gives a graphical representation for the transfer of genetic information in crosses. The gametes from the parents are represented on the top and the left sides of the Punnett square.

4. What is represented in the boxes of the Punnett square?
a) Gametes of male parent
b) Gametes of female parent
c) Genotype of the offspring produced
d) Genotype of all possible offsprings

Explanation: In the Punnett square, the boxes are filled with the offsprings that can be produced, in principle, from the combinations of gametes of both parents. This can be used to determine the genotypic and phenotypic ratios of the progeny.

5. What gametes are produced by a Vv heterozygous plant?
a) 50% V and 50% v
b) 75% V and 25% v
c) 25% V and 75% v
d) 100% V and 0% v

Explanation: The process of segregation that occurs during meiosis is a random process. Thus the gametes will have 50% of each allele. Hence Vv heterozygous plant would produce 50% V and 50% v containing gametes.

6. Upon self-fertilization of Aa with itself, the probability of A gamete fusing A and a gamete is equal.
a) True
b) False

Explanation: The probability of occurrence of A and a is equal; each has a chance of 50%. Fertilization is also a random process. Thus, A fertilizing A or a gamete has an equal probability of 50%.

7. Which of the following is the correct number of offsprings produced by self-fertilization of a heterozygous pea plant for a trait that exhibits Mendelian genetic pattern?
a) 250 Homozygous dominant, 500 Heterozygous dominant and 250 Homozygous recessive
b) 125 Homozygous dominant, 125 Heterozygous dominant and 125 Homozygous recessive
c) 500 Homozygous dominant, 501 Heterozygous dominant and 250 Homozygous recessive
d) 500 Homozygous dominant, 250 Heterozygous dominant and 500 Homozygous recessive

Explanation: Self-fertilization of heterozygote will lead to 25% homozygous dominants, 25% homozygous recessive, and 50% heterozygous dominants. This is satisfied if the population sampled has 250 homozygous dominant and recessive plant and 500 heterozygous dominant plants.

8. The ratio of genotypes observed in progeny after a cross has been performed is called ________
a) genotypic ratio
b) phenotypic ratio
c) absolute ratio
d) relative ratio

Explanation: The genotypes of a progeny can be studied using Punnett square. The ratio of different genotypes is called the genotypic ratio.

9. The ratio of phenotypes observed in progeny after a cross has been performed is called ________
a) genotypic ratio
b) phenotypic ratio
c) absolute ratio
d) relative ratio

Explanation: The phenotypes of a progeny can be studied by manually counting the offsprings. The ratio of different phenotypes defines the phenotypic ratio of the cross.

10. What generation of Mendelian cross has a phenotypic ratio of 3:1?
a) F0
b) F1
c) F2
d) F3

Explanation: The phenotypic ratio is the ratio of different phenotypes observed in the progeny. In the F2 generation of a Mendelian cross, there are 75% plants with dominant phenotype and 25% plants with a recessive phenotype. This gives a phenotypic ratio of 3:1.

11. According to the law of dominance, what are the discrete units that control the characters?
a) Factors
b) Multipliers
c) Divisors
d) Remainders

Explanation: The law of dominance states characters encoded by discrete units. Mendel called these factors, which he believed transferred from parents during progeny during fertilization. These are now known as genes.

12. The factors that Mendel postulated occur in triplets.
a) True
b) False

Explanation: The Mendels’ factors are genes. These exist in a pair. These can be the same or different, which are termed as alleles.

13. Which of the following is not a statement of the principle of dominance?
a) Factors occur in pairs
b) One factor is dominant over the other
c) Factors control characters
d) Factors segregated during the process of meiosis

Explanation: The principle of dominance does not state the segregation of factors. This is stated by the law of segregation or separation.

14. A homozygous parent produces gametes that are ______; while the heterozygous parent produces gametes that are _______
a) similar; similar
b) similar; dissimilar
c) dissimilar; dissimilar
d) dissimilar; similar

Explanation: The law of segregation states that the factors separate during gamete formation. Thus a homozygous parent will produce gametes that have similar factors while the heterozygous parent would produce gametes with dissimilar alleles.

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