This set of Class 12 Biology Multiple Choice Questions & Answers (MCQs) focuses on “Chromosomal Theory of Inheritance-2” for MBBS Entrance Exam.
1. What is called a reduction division?
a) Mitosis
b) Meiosis
c) Mitrosis
d) Cleavage
View Answer
Explanation: During the process of meiosis, each daughter cell gets only half the original chromosomal content. Hence it is called the reduction division.
2. Chromosomes occur _________; genes occur _________
a) singly, singly
b) singly, in pairs
c) in pairs, singly
d) in pairs, in pairs
View Answer
Explanation: A diploid cell has double the set of chromosomal content. Hence there are two copies for each chromosome present. These are called homologous chromosomes. Now, genes are fragments of DNA present on the chromosomes. Hence they also occur in pairs, with one gene present on each homologous chromosomes.
3. Alleles of a gene are located on ________
a) homologous chromosomes
b) heterologous chromosomes
c) homologous chromatids
d) heterologous chromatids
View Answer
Explanation: The alleles of a gene compete or support each other for expression. Hence, they have to be present at homologous sites and on homologous chromosomes.
4. The duplication of chromosomes occurs during _____
a) G1 phase
b) G2 phase
c) G0 phase
d) G3 phase
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Explanation: G2 phase is the biosynthetically active phase. During this phase, a lot of energy is spent by the cell to grow and duplicate its genomic content.
5. When does the first segregation of chromosomes occur during meiosis?
a) Meiosis I Anaphase
b) Meiosis I Telophase
c) Meiosis II Anaphase
d) Meiosis II Telophase
View Answer
Explanation: The segregation of chromosomes occurs when the spindle fibers pull the fibers pull the chromosomes to the poles and away from the metaphase plate. The first such segregation occurs during meiosis I Anaphase.
6. When does the second segregation of chromosomes occur during meiosis?
a) Meiosis I Anaphase
b) Meiosis I Telophase
c) Meiosis II Anaphase
d) Meiosis II Telophase
View Answer
Explanation: Meiosis takes place in two phases and involves the separation of chromosomes twice. The second segregation occurs in the Anaphase of Meiosis II.
7. When does the first segregation of genes occur during meiosis?
a) Meiosis I Anaphase
b) Meiosis I Telophase
c) Meiosis II Anaphase
d) Meiosis II Telophase
View Answer
Explanation: Genes occur in pairs. At the start of meiosis, there are four copies of each gene. They are segregated first during Anaphase I, where each pole receives a pair of each gene.
8. When does the second segregation of chromosomes occur during meiosis?
a) Meiosis I Anaphase
b) Meiosis I Telophase
c) Meiosis II Anaphase
d) Meiosis II Telophase
View Answer
Explanation: Genes are present as four copies, two of each allele at the onset of meiosis. They are segregated twice: first during Anaphase I and second during Anaphase II. At the end of which, each daughter cell has only one copy of the gene.
9. If the cell at G1 phase at 2 Giga base pairs of DNA, what is the DNA content of the cell right before Telophase II?
a) 1 Giga base pairs
b) 2 Giga base pairs
c) 3 Giga base pairs
d) 4 Giga base pairs
View Answer
Explanation: Cell at G1 phase has a pair of chromosomes. By the end of Anaphase II, it still has a pair of chromosomes. Hence the DNA content would be almost the same as at the time of G1.
10. If the cell at G1 phase at 2 Giga base pairs of DNA, what is the DNA content of the cell right before Telophase I?
a) 1 Giga base pairs
b) 2 Giga base pairs
c) 3 Giga base pairs
d) 4 Giga base pairs
View Answer
Explanation: Cells undergo DNA duplication during G2 phase. This is split at the end of Meiosis I. However, until the Telophase I, the cell retains twice the DNA content as at the onset of G1.
11. If the cell at G1 phase at 2 Giga base pairs of DNA, what is the DNA content of the cell right after Telophase II?
a) 1 Giga base pairs
b) 2 Giga base pairs
c) 3 Giga base pairs
d) 4 Giga base pairs
View Answer
Explanation: The cell starts with two copies of each chromosome during the G1 phase. G2 phase witnesses DNA duplication. However, by the end of Meiosis II, cell splits into four, and each germ cell receives a single copy of each chromosome. Thus, the DNA content at the end of meiosis would be half what it was at the time of onset.
12. The alignment of the chromosome pairs at the metaphase plate during Meiosis I is dependent on other chromosomal pairs.
a) True
b) False
View Answer
Explanation: The alignment of chromosomal pairs is independent of each other. This is what leads to the statement of the chromosomal basis of inheritance.
13. What phase of Meiosis results in the different combinations of chromosomes occurring in the germ cells?
a) Metaphase I
b) Anaphase I
c) Metaphase II
d) Anaphase II
View Answer
Explanation: The independent segregation of chromosome pairs occurs during the Metaphase I. This leads to the variations in the daughter cells or germ cells.
14. The variations observed in the daughter cells arise during Metaphase I.
a) True
b) False
View Answer
Explanation: The Metaphase I involve the independent segregation of the chromosomal pairs by their independent arrangement at the Metaphase plate. This led to the variations observed in the daughter cells.
15. What is each copy of the duplicated chromosome called?
a) Chromatid
b) Chromomere
c) Kinetochore
d) Chromonema
View Answer
Explanation: The chromosomes duplicate during the G2 phase of the cell cycle. Each copy of the chromosome is identical and is hence called a chromatid. The G2 phase is followed by M phase or meiotic phase, where the chromatids align together at the metaphase plate followed by segregation during the anaphase.
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