Analyse the events during every stage of cell cycle and notice how the following two parameters change
[question] Question. Analyse the events during every stage of cell cycle and notice how the following two parameters change (i) Number of chromosomes (N) per cell (ii) Amount of DNA content (C) per cell [/question] [solution] Solution: During meiosis, the number of chromosomes and the amount of DNA in a cell change. (i) Number of chromosomes (N) per cell During anaphase I of the meiotic cycle, the homologous chromosomes separate and start moving toward their respective poles. As a result, the bi...
Can there be DNA replication without cell division?
[question] Question. Can there be DNA replication without cell division? [/question] [solution] Solution: There can be DNA replication without cell division. During cell division, the parent cell gets divided into two daughter cells. However, if there is a repeated replication of DNA without any cell division, then this DNA will keep accumulating inside the cell. This would increase the volume of the cell nucleus, thereby causing cell expansion. An example of DNA duplication without cell divisio...
Can there be mitosis without DNA replication in S phase?
[question] Question. Can there be mitosis without DNA replication in S phase? [/question] [solution] Solution: Mitotic cell division cannot take place without DNA replication in S phase. Two important events take place during S phase – one is the synthesis or duplication of DNA and the other is the duplication of the centriole. DNA duplication is important as it maintains the chromosome number in the daughter cells. Mitosis is an equational division. Therefore, the duplication of DNA is an impor...
Discuss with your teacher about
[question] Question. Discuss with your teacher about (i) haploid insects and lower plants where cell-division occurs, and (ii) some haploid cells in higher plants where cell-division does not occur. [/question] [solution] Solution: (i) In some insects and lower plants, fertilization is immediately followed by zygotic meiosis, which leads to the production of haploid organisms. This type of life cycle is known as haplontic life cycle. (ii) The phenomenon of polyploidy can be observed in some hapl...
What is the significance of meiosis?
[question] Question. What is the significance of meiosis? [/question] [solution] Solution: Meiosis is the process involving the reduction in the amount of genetic material. It comprises two successive nuclear and cell divisions, with a single cycle of DNA replication. As a result, at the end of meiosis II, four haploid cells are formed. Significance of meiosis 1. Meiosis maintains the chromosome number from generation to generation. It reduces the chromosome number to half so that the process of...
List the main differences between mitosis and meiosis.
[question] Question. List the main differences between mitosis and meiosis. [/question] [solution] Solution: [/solution]...
Distinguish anaphase of mitosis from anaphase I of meiosis.
[question] Question. Distinguish anaphase of mitosis from anaphase I of meiosis. [/question] [solution] Solution: \ [/solution]...
Find examples where the four daughter cells
[question] Question. Find examples where the four daughter cells from meiosis are equal in size and where they are found unequal in size. [/question] [solution] Solution: (a) Spermatogenesis or the formation of sperms in human beings occurs by the process of meiosis. It results in the formation of four equal-sized daughter cells. (b) Oogenesis or the formation of ovum in human beings occurs by the process of meiosis. It results in the formation of four daughter cells which are unequal in size. [...
How does cytokinesis in plant cells differ from that in animal cells?
[question] Question. How does cytokinesis in plant cells differ from that in animal cells? [/question] [solution] Solution: [/solution]...
Describe the following:
[question] Question. Describe the following: (a) synapsis (b) bivalent (c) chiasmata Draw a diagram to illustrate your answer. [/question] [solution] Solution: (a) Synapsis The pairing of homologous chromosomes is called synapsis. This occurs during the second stage of prophase I or zygotene. (b) Bivalent Bivalent or tetrad is a pair of synapsed homologous chromosomes. They are formed during the zygotene stage of prophase I of meiosis. (c) Chiasmata Chiasmata is the site where two non-sister chr...
Why is mitosis called equational division?
[question] Question. Why is mitosis called equational division? [/question] [solution] Solution: Mitosis is the process of cell division wherein the chromosomes replicate and get equally distributed into two daughter cells. The chromosome number in each daughter cell is equal to that in the parent cell, i.e., diploid. Hence, mitosis is known as equational division. [/solution]...
What is G0 (quiescent phase) of cell cycle?
[question] Question. What is $\mathrm{G}_{0}$ (quiescent phase) of cell cycle? [/question] [solution] Solution: $\mathrm{G}_{0}$ or quiescent phase is the stage wherein cells remain metabolically active, but do not proliferate unless called to do so. Such cells are used for replacing the cells lost during injury. [/solution]...
Describe the events taking place during interphase.
[question] Question. Describe the events taking place during interphase. [/question] [solution] Solution: Interphase involves a series of changes that prepare a cell for division. It is the period during which the cell experiences growth and DNA replication in an orderly manner. Interphase is divided into three phases. (i) $G_{1}$ phase (ii) $S$ phase (iii) $\mathrm{G}_{2}$ phase $\mathrm{G}_{1}$ phase $-$ It is the stage during which the cell grows and prepares its DNA for replication. In this ...
Distinguish cytokinesis from karyokinesis.
[question] Question. Distinguish cytokinesis from karyokinesis. [/question] [solution] Solution: [/solution]...
What is the average cell cycle span for a mammalian cell?
[question] Question. What is the average cell cycle span for a mammalian cell? [/question] [solution] Solution: The average cell cycle span for a mammalian cell is approximately 24 hours. [/solution]...