Biology MCQs for Class 12 with Answers Chapter 3 ( Inheritance and Variation )

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MCQ on Inheritance and Variation Class 12: 


1. Phenotypic ratio of incomplete dominance in Mirabilis jalapa.
a. 2: 1 : 1
b. 1 : 2 : 1
c. 3 : 1
d. 2 : 2
Answer: b ( 1:2:1)

ExplanationIn four o’clock plants (Mirabilis jalapa) we can Gross a plant with red flower petales with another with white petales, the offspring have pink flower petales. If these pink flowered F1 plants are crossed, the F2 plants appear in a ratio of 1:2:1, having red, pink or white petals, respectively.


2. In dihybrid cross, F2 generation offsprings show four different phenotypes while the genotypes are …………….
a. six
b. nine
c. eight
d. sixteen
Answer: b ( nine )

Explanation: The two different phenotypes in the dihybrid cross are seed color and seed shape. One plant is homozygous for the dominant traits of yellow seed color (YY) and round seed shape (RR). The genotype can be expressed as (YYRR). … The F2 progeny exhibits four different phenotypes and nine different genotypes.

3. A cross between an individual with unknown genotype for a trait with recessive plant for that trait is …………..
a. back cross
b. reciprocal cross
c. monohybrid cross
d. test cross
Answer: d ( Test cross )

ExplanationA cross between an individual with unknown genotype for a trait with recessive plant for that trait is test cross. – Test cross is cross between individual with unknown genotype and an individual with a phenotypically recessive individual.

4. When phenotypic and genotypic ratios are the same, then it is an example of …………
a. incomplete dominance
b. complete dominance
c. Multiple alleles
d. cytoplasmic inheritance
Answer: a ( Incomplete Dominance) 

Explanation: When phenotypic and genotypic ratio is the samethen it is an example of *incomplete dominance*. – Incomplete dominance is a form of intermediate inheritance in which one allele for a specific trait is not completely expressed over its paired allele.

5. If the centromere is situated near the end of the chromosome, the chromosome is called…………….
a. Metacentric
b. Acrocentric
c. Sub-Metacentric
d. Telocentric
Answer: d (Telocentric)

Explanation: The centromere is situated at the tip of the chromosome it is called the telocentric chromosome. The centromere is the position of a chromosome that joined a pair of sister chromatids. Position of the centromere in a chromosome classified the type chromosome.

6. Chromosomal theory of inheritance was proposed by …………….
a. Sutton and Boveri
b. Watson and Crick
c. Miller and Urey
d. Oparin and Halden
Answer: a ( Sutton & Boveri )
 
ExplanationTheodor Boveri and Walter Sutton are the scientists credited with an extension of Mendel’s laws, known as the chromosome theory of inheritance. In essence, this theory, which was developed in the early 1900s, explains what Mendel observed in his pea plants, otherwise known as the Boveri and Sutton chromosome theory.


7. If the genes are located in a chromosome as p-q-r-s-t, which of the following gene pairs will have least probability of being inherited together?
a. p and q
b. r and s
c. s and t
d. p and s
Answer: d


8. Find the mis match pair :
a. Down’s syndrome = 44 + XY
b. Turner’s syndrome = 44 + XO
c. Klinefelter syndrome = 44 + XXY
d. Super female = 44 + XXX
Answer: d (Super Female)

9. A colourblind man marries a woman, who is homozygous for normal colour vision ,the probability of their son being colourblind is
a. 0%
b. 25%
c. 50%
d. 100%
Answer: a (0)

Explanation: Colour blind man (XcY) with Normal homozygous woman (XX) → Son (XY) (normal vision) Son receives Y chromosome from father and X chromosomes from mother, hence he has zero probability of being colour-blind.


10. Which of the following is an example of an inherited trait?
a. The ability to play a musical instrument
b. The ability to solve complex mathematical problems
c. The ability to ride a bicycle
d. The ability to speak multiple languages
Answer: d) The ability to speak multiple languages

Explanation: Inherited traits are passed down from parents to offspring through genes. The ability to speak multiple languages is a trait that can be influenced by genetic factors and can be inherited.

11. What is the term used to describe the different forms of a gene?
a. Allele
b. Chromosome
c. DNA
d. Mutation
Answer: a) Allele

Explanation: Alleles are different forms of a gene that occupy the same position (locus) on a chromosome. They can result in different variations of a trait.

12. Which of the following best describes the term “inheritance”?
a. The passing on of genetic information from one generation to the next.
b. The interaction between genes and the environment.
c. The process of DNA replication.
d. The creation of new genetic variations.
Answer: a) The passing on genetic information from one generation to the next.

Explanation: Inheritance refers to the transmission of genetic information, including traits and characteristics, from parents to offspring.

13. What is the main source of genetic variation in a population?
a. Gene mutation.
b. Environmental factors.
c. Genetic drift.
d. Natural selection.
Answer: a) Gene mutation.

Explanation: Gene mutation is the primary source of new genetic variation within a population. Mutations can occur spontaneously and introduce new genetic traits, which can then be passed on to future generations.

14. Which of the following describes a homozygous genotype?
a. A genotype with two different alleles for a particular gene.
b. A genotype with two identical alleles for a particular gene.
c. A genotype with three alleles for a particular gene.
d. A genotype with no alleles for a particular gene.
Answer: B) A genotype with two identical alleles for a particular gene.

Explanation: Homozygous genotype refers to a condition in which an individual possesses two identical alleles for a particular gene. For example, “AA” or “aa” are homozygous genotypes.

15. The observable traits or characteristics of an organism are known as:
a. Genotype.
b. Phenotype.
c. Alleles.
d. Genes.
Answer: b) Phenotype.

Explanation: Phenotype refers to the observable traits or characteristics of an organism, such as its physical appearance, behavior, or biochemical properties.

16. A child has blood type O, and the father has blood type A. What could be the possible blood types of the child’s mother?
a. A or O
b. A, B, or AB
c. O only
d. B or AB
Answer: a) A or O

Explanation: Blood type O is a recessive trait. If the child has blood type O, it means they received an O allele from both parents. The father has blood type A, which means he can have either AA or AO genotype. The child’s mother could have blood type A (AA genotype) or be a carrier for blood type O (AO genotype).

17. Which of the following is an example of a phenotypic variation?
a. Eye color
b. Genotype
c. Blood type
d. DNA sequence
Answer: a) Eye color

Explanation: Phenotypic variation refers to the observable physical characteristics or traits of an organism. Eye color is an example of a phenotypic variation because it is a visible characteristic that can vary among individuals.

I hope this MCQ on inheritance and variation class 12 with answers helps! Let me know if you have any more questions.

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