Chapter 10 - Cell Cycle and Cell Division

Cell Cycle and Cell Division explains how cells grow, duplicate their genetic material and divide. NCERT Class 11 Biology Chapter 10 covers the stages of the cell cycle, mitosis, meiosis and the biological significance of each type of division.

Teachoo’s Chapter 10 resources include step-by-step notes, labelled diagrams, NCERT solutions, important questions and MCQs for school exams and NEET. The chapter is taught as a continuous sequence so students can follow what happens to chromosomes, DNA, nuclei and cytoplasm at every stage.

The cell cycle consists of interphase and the M phase. Interphase is metabolically active and includes:

• G1 phase, when the cell grows and performs normal functions

• S phase, when DNA replicates

• G2 phase, when the cell prepares for division

Some cells may leave the active cycle and enter a quiescent stage called G0. A crucial distinction is that DNA content doubles during S phase, but chromosome number does not double because each chromosome simply forms two sister chromatids.

The M phase includes karyokinesis, division of the nucleus, and cytokinesis, division of the cytoplasm. Mitosis proceeds through prophase, metaphase, anaphase and telophase. Chromosomes condense, attach to spindle fibres, align at the equatorial plate, separate at the centromere and move to opposite poles before new nuclei form.

Cytokinesis differs in animal and plant cells. Animal cells usually form a cleavage furrow, while plant cells form a cell plate that develops into a new cell wall. Mitosis produces genetically similar daughter cells and supports growth, repair, replacement and asexual reproduction.

Meiosis consists of two successive divisions after one round of DNA replication. Meiosis I is reductional because homologous chromosomes separate, while meiosis II is equational because sister chromatids separate.

Prophase I is divided into leptotene, zygotene, pachytene, diplotene and diakinesis. Synapsis produces bivalents, crossing over occurs between non-sister chromatids, and chiasmata become visible. These events generate genetic variation and are central to sexual reproduction.

Students must compare mitosis and meiosis in terms of:

• Number of divisions

• Number and ploidy of daughter cells

• Synapsis and crossing over

• Structures separated at anaphase

• Genetic similarity or variation

• Location and biological function

Teachoo helps students practise chromosome-count and DNA-content questions, stage identification, diagram labelling, event sequencing and assertion-reason questions. These skills are important because examination questions often describe an event and ask students to identify the stage rather than directly naming it.

The best way to revise is to track one pair of homologous chromosomes through every stage. Note whether DNA has replicated, whether homologues are paired, whether centromeres divide and whether the cell is diploid or haploid. This prevents the common mistake of memorising chromosome diagrams without understanding what changes.

Cell division connects directly with growth, reproduction, inheritance, variation and development. A strong command of this chapter makes later genetics and reproductive-biology concepts far easier.