This set of Biology Multiple Choice Questions & Answers (MCQs) focuses on “Cell Cycle and Division – Meiosis-1”.
1. Which of these statements is not true about fertilization?
a) The gametes are haploid
b) Gametes develop from diploid cells
c) It involves the fusion of two gametes
d) Gametes have an incomplete set of chromosomes
Explanation: Fertilization involves the fusion of two gametes to produce an offspring. These gametes develop from diploid cells and are haploid. However, they possess the complete set of chromosomes.
2. Which of these processes ensure the haploid phase of life cycle?
Explanation: The haploid phase of life cycle occurs when the total chromosome number inside the cell is reduced to half. It occurs by the process of meiosis. Fertilization restores the diploid phase of life cycle.
3. Which of these processes involve meiosis?
Explanation: Gametogenesis is the formation of gametes from some specialized diploid cells. Since gametes are haploid, gametogenesis involves in the reduction of chromosome number by half through meiosis.
4. Meiosis involves one cycle of ______
a) DNA replication
d) separation of chromosomes
Explanation: Meiosis is divided into two stages- meiosis I and meiosis II. In each stage, the cell undergoes separation of chromosomes during anaphase I and anaphase II, cytokinesis and karyokinesis.
5. Which of these undergo recombination?
a) Homologous chromosomes
b) Non-homologous chromosomes
c) Non-sister chromatids
d) Sister chromatids
Explanation: Non-sister chromatids of homologous chromosomes undergo recombination during meiosis, during which their genetic material is exchanged. This increases the genetic diversity of the species.
6. How many cells are formed at the end of meiosis I?
a) 2 haploid cells
b) 4 diploid cells
c) 2 diploid cells
d) 4 haploid cells
Explanation: Meiosis 1 involves one round of cell division in which the tetrad is separated into two daughter cells. Hence, from 4n of tetrad, two daughter cells each having 2n chromosomes are formed.
7. Arrange the phases of prophase I in order.
a) Leptotene → Zygotene → Pachytene → Diplotene
b) Zygotene → Leptotene → Pachytene → Diplotene
c) Leptotene → Pachytene → Zygotene → Diplotene
d) Zygotene → Leptotene → Diplotene → Pachytene
Explanation: Prophase 1 is the first stage of meiosis. It is the first step of meiosis 1. It is divided into four sub-phases-namely, Leptotene, Zygotene, Pachytene and Diplotene. Diplotene is followed by diakinesis.
8. Compaction of chromosomes occurs during ______
Explanation: Chromosomes have to become decondensed and compact before they can undergo cell division. Hence, chromosomal compaction occurs during the leptotene stage of prophase I of meiosis I.
9. What is the chromosomal association process in zygotene called?
Explanation: Zygotene is the second stage of prophase I of meiosis I. The compact chromosomes begin to associate with each other during this phase, and this association process is known as synapsis.
10. The duration of zygotene is shorter than that of pachytene. True or false?
Explanation: Zygotene is the second stage of prophase I while pachytene is the third stage. Tetrad formation takes place during zygotene while crossing over and recombination take place during pachytene stage.
11. During which stage of prophase I does synapsis occur?
Explanation: Synapsis is the process of association of compact chromosomes after the first phase of prophase I, leptotene. It occurs in the second phase known as the zygotene phase. The chromosomes pair with each other during synapsis.
12. Which of these following statements is false about synapsis?
a) Pairs of homologous chromosomes are formed
b) It occurs during zygotene
c) It results in tetravalent formation
d) It is accompanied by synaptonemal complex formation
Explanation: Synapsis is the process of chromosomal association that takes place in the zygotene stage of prophase I. It results in pairing of homologous chromosomes and involves synaptonemal complex formation. It results in bivalent formation.
13. During which stage do the chromatids of a bivalent become distinct?
Explanation: Bivalent or tetrad formation takes place during the zygotene stage of prophase I, after synapsis has occurred and homologous chromosomes form pairs. However, the bivalent is distinct only in the next stage, pachytene.
14. Crossing over takes place during _____
Explanation: Crossing over takes place after tetrad or bivalent formation by the process of synapsis during zygotene. Hence, crossing over takes place during pachytene. Crossing over leads to genetic diversity.
15. Which of these is true regarding crossing over?
a) Exchange occurs between non-homologous chromosomes
b) It involves recombination nodules
c) It is not mediated by enzymes
d) It occurs during zygotene
Explanation: Crossing over takes place during the pachytene stage of prophase I. It is enzyme mediated and involves recombination nodules. Exchange of genetic material occurs between homologous chromosomes.
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