This set of Class 12 Biology Chapter 5 Multiple Choice Questions & Answers (MCQs) focuses on “Inheritance of One Gene-2”.
1. Self-pollination of F1 progeny will result in a new filial generation called _______
Explanation: The filial generations are numbered in relation to the parental generations. The self-pollination of F1 progeny will produce a generation that is two-step distant from the parental generation. Hence it will be F2 generation.
2. What are the possible phenotypes that can be observed after self-crossing violet flowered pea plants?
a) All violet
b) All white
c) 25% violet and 75% white
d) 25% white and 75% violet
Explanation: Violet is dominant over white. Self-crossing of violet flowered plants will produce 25% recessive plants, which will have white-flowers.
3. In Mendelian crosses, the F2 progeny exhibits a recessive phenotype and a blended phenotype.
Explanation: Mendelian crosses do not exhibit blending of phenotypes. These are performed on true-breeding parents, and the locus encoding the traits does not show any crossover. The phenotypes of F are dominant and recessive.
4. Which of the following was not observed in F2 progeny of true-breeding tall and dwarf plants?
a) Homozygous tall plants
b) Heterozygous tall plants
c) Homozygous dwarf plants
d) Heterozygous dwarf plants
Explanation: The F2 progeny has both dwarf and tall plants. 25% of them are homozygous tall, 50% are heterozygous tall, and 25% are homozygous dwarf. Dwarfness is a recessive trait and thus cannot be expressed in the heterozygous state.
5. Based on his experiments on pea plants, what were the things that he suspected of being transferred across generations?
Explanation: Mendel studied pea plant inheritance of traits. He observed a pattern in the way traits were passed from parents to offsprings. Based on these, he suspected the existence of “factors” that need to be transferred through gametes from parents to offsprings.
6. What exactly are Mendel’s factors?
Explanation: The factors that Mendel observed were forgotten for decades to come. Later experiments, independent of these studies of Mendel, led to the discovery of genes as the source of transfer of information that codes for traits. Later it was found that Mendel’s factors were indeed genes.
7. What are the copies of genes that code for different phenotypes called?
Explanation: Alleles are the copies of genes that code for contrasting traits. They are different forms of the same gene. For an allele to express, it should have a fitness benefit over its counterpart allele.
8. To represent a genotype, the dominant allele is represented by a capital letter and the recessive allele by a small letter.
Explanation: The convention used to write the genotype uses a single letter to represent an allele. Capital letters symbolize dominant alleles. The corresponding small letters are used to represent recessive alleles.
9. Which zygosity has the same allelic pair of genes?
Explanation: Homozygosity refers to the state of genes that have both copies of genes or alleles as the same alleles. Heterozygous condition has two different alleles.
10. VV, Vv and vv are _______, while violet and white are _________
a) genotypes, phenotypes
b) phenotypes, genotypes
c) genotypes, genotypes
d) phenotypes, phenotypes
Explanation: The genotypes refer to the allelic composition of a particular gene. Thus VV, Vv, and vv are the genotypes. Violet and white are the phenotypes. These refer to the expressed trait.
11. The factor expressed only in homozygous state is called _________
Explanation: A recessive factor cannot express itself when a dominant factor is present. It can only express when the organism has two copies of it. Thus, it requires homozygous state to express itself.
12. What is the cross between VV and vv called?
a) Monohybrid cross
b) Dihybrid cross
c) Monogamous cross
d) Digamous cross
Explanation: The offsprings produced from this cross are heterozygous for only one gene, which encodes for tallness. Thus, the cross is called a monohybrid cross.
13. What kind of a process is the segregation of alleles during meiosis?
Explanation: Segregation of alleles leads to each gamete having only a single allele at the end of meiosis. This process is purely random or stochastic. Thus, the probability of a gamete having either alleles is 50%.
14. If the F1 generation produced by a cross between axial and terminal flower-bearing plants produces only axial flowers, the F2 progeny produced by the self-crossing of F1 will also produce only axial flowers.
Explanation: The F1 progeny has only axial flowers, which imply that axial trait is dominant over the terminal trait. However, the F1 progeny are heterozygous. Upon self-crossing, 25% of the F2 progeny will be homozygous for the recessive trait, resulting in the formation of 3:1 ratio of axial flower-bearing to terminal flower-bearing plants.
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