NEET Important Chapter - Cell Cycle and Cell Division

This article includes the notes of the chapter ‘Cell cycle and Cell Division’ as per the NEET 2022 syllabus for biology. NEET aspirants should read these NEET notes as they contain the  main and important topics for the last minute revision. 

You will also get to know about the important topics of the chapter and all the information according to the exam pattern. By revising this NEET Notes and important questions of Cell Cycle and Cell Division, one can gather more knowledge related to the topics such as what is cell cycle and cell division, what are the phases of cell division, what is mitosis and significance, what is meiosis and its significance, the difference between meiosis and mitosis, what is meiosis I and meiosis II and also significance of cell division, significance of cell cycle and phases of cell cycle can be studies in this document. 

Important Topics of Cell Cycle and Cell Division

• Phases of Cell Cycle

• Mitosis and Its Significance

• Meiosis 

• Stages of Meiosis I

• Stages of Meiosis II

• Mitosis and Meiosis Difference

Important Concepts

Cell Cycle and Cell Division 

A series of events that takes place in a cell as it grows and divides. Cell division is the dividing up of cells and the formation of two daughter cells from a single cell.

Phases of Cell Cycle 

1. Interphase

Between two successive M phases of cell division interphase is the period of time lapse, then replication of DNA takes place and it is further divided into three phases they are: G1, S, G2

G1 Phase:  The gap or space between previous mitosis and DNA replication of the next upcoming cycle is called G1 phase.

S Phase: The cell doubles and centriole duplicates in the DNA content. but the number of chromosomes remains the same, it is very important to notice that.

G2 Phase:  In this phase the cell continues to grow rapidly and prepare itself  for mitosis. There are many cells in adult human beings which they won't divide. For example, the heart cells are divided occasionally only to replace dead and injured cells, and those cells will enter an inactive phase called the G0 stage of the cell cycle. It is also called the quiescent stage.

2. M Phase  

The phase where the actual cell division will occur is known as the M phase. The actual number of daughter cells and parent cells remains the same and it is also called equational division.

Karyokinesis is the nuclear division followed by cytokinesis, which is the division of the cytoplasm to give rise to two daughter cells.

1. Mitosis 

Mitosis is an equational division, that is the number of chromosomes in a daughter cell is equal to the number of chromosomes in parent cells.

2. Meiosis 

Meiosis is called reductional division as the number of chromosomes is halved in daughter chromosomes. Meiosis has 2 phases they are, 

• Meiosis I

• Meiosis II

Solved Examples from Chapter - Cell Cycle and Cell Division 

1. In an organism does the duration affect the cell cycle?

Ans: The external factors like temperature, food and oxygen and type of cell  affect the duration. The time period for G, S, G, and M-phase in different species under specific environmental conditions like 20 min for bacterial cells, 10 hours for intestinal epithelial cells, 20 hours for onion root tip cells, etc. This represents the time needed for each cell has been set priorly within each organism’s cell.

2. Do eukaryotic cells divide in mitosis?

Ans: Mitosis is a process where the number of cells increases but the chromosome number remains the same, so it is called equational division. In this type of cell division, the two daughter cells are produced by a single parent cell, which are similar to the parent cells genetically. So this type of division can be used in the multiplication or rapid proliferation of eukaryotic cells.

Solved Problems of Previous Year Question from Chapter

1. Anaphase promoting complex (APC) is a protein degradation machinery necessary for proper mitosis of animal cells. If APC is defective in a human cell, which of the following is expected to occur? 

a) Chromosomes will not condense 

b) Chromosomes will be fragmented 

c) Chromosomes will not segregate 

d) Recombination of chromosome arms will occur 

Ans: Chromosomes will not segregate 

The centromere splits and the chromatids move towards the poles in anaphase stage, this process is helped by APC. so defects in APC may fail to segregate the chromosomes. 

2. DNA replication in bacteria occurs 

a) During S-phase

b) Within nucleolus 

c) Prior to fission

d) Just before transcription 

Ans: Prior to fission

DNA replication is the formation of new DNA from parent DNA. DNA replication is prior to fission in bacteria. With the help of mesosomes, it occurs.

3. Which of the following options gives the correct sequences of events during mitosis? 

a) Condensation→ nuclear membrane disassembly →crossing over→ Segregation → telophase

b) Condensation → nuclear membrane disassembly → arrangement at equator → centromere division → Segregation → telophase 

c) Condensation → crossing over → nuclear membrane disassembly→ Segregation → telophase 

d) Condensation → arrangement at equator centromere division → Segregation → telophase 

Ans: Condensation → nuclear membrane disassembly → arrangement at equator → centromere division → Segregation → telophase 

Mitotic division is a division in which a single cell divides to form 2 daughter cells. According to the question, the division starts from a single cell.

In the first division single cell is divided into two and in the second division those 2 cells divide into 4, in the third division 4 cells divide into 8, in the fourth division 8 cells divide into 16, and in the fifth division, 16 cells divide into 32, in sixth division 32 cells divide into 64 and in seventh division 64 cells divide into 128. So 7 divisions are required to form 128 cells. Mitosis occurs in Condensation → nuclear membrane disassembly → arrangement at equator → centromere division → Segregation → telophase 

Practice Questions

1. The paired homologous chromosomes get shortened and thickened in which stage of cell division? 

Ans: The paired homologous chromosomes get shortened and thickened in the pachytene stage.

2. Which is not true for anaphase?

a) Golgi body and endoplasmic reticulum are reformed

b) Chromosomes move to opposite poles

c) Spindle poles move farther apart

d) Centromeres split and chromatids separate

Ans: Golgi body and endoplasmic reticulum are reformed.

The splitting of centromere, forming of two sister chromatids and their movements towards the opposite poles can be mainly indicated in the anaphase stage these movements of sister chromatids are brought up by the spindle fibres. The Golgi body and ER reappear in the cytokinesis stage but not in the anaphase stage.

Conclusion

This article includes all important information in the chapter ‘Cell Cycle and Cell Division’. You will learn about the significance of the cell cycle and cell division and phases of the cell cycle can be studied in this article as well. One can understand the function of cell division by thoroughly reading these notes. So this file is beneficial to students who are preparing for NEET 2022. Surely practice the question on your own to check your knowledge of this chapter.