CBSE Class 11 Biology Notes Chapter 10 Cell Cycle and Cell Division

CBSE Class 11 Biology Notes Chapter 10 Cell cycle and Cell Division Notes: Chapter 10 Cell cycle and Cell division notes are important for the students who are preparing for the entrance exams. This chapter is one of the important chapters for the preparation of Board exams as well.

CBSE Class 11 Biology Notes Chapter 10 Overview

What is a Cell Cycle?

Phases of Cell Cycle

Interphase

• The G1 phase occurs after cell division (mitosis) and before DNA replication initiation. During G1, the cell grows and is metabolically active but does not replicate its DNA.
• The S phase, or synthesis phase, is when DNA replication happens, doubling the amount of DNA per cell. Despite DNA doubling, the chromosome number remains the same as in G1. In animal cells during S phase, DNA replication begins in the nucleus, and centrioles duplicate in the cytoplasm.
• The G2 phase involves protein synthesis in preparation for mitosis while cell growth continues. Some adult animal cells, like heart cells, and others divide only as needed to replace lost cells, exiting G1 to enter a non-dividing state called G0. Cells in G0 remain metabolically active but only proliferate when needed by the organism.

M Phase

• Chromosomal condensation into compact mitotic chromosomes, each consisting of two chromatids attached at the centromere.
• Centrosomes move to opposite poles, radiating microtubules called asters.

Key features of Metaphase are:

• Spindle fibers attach to chromosome kinetochores.
• Chromosomes move to the spindle equator and align along metaphase plate via spindle fibers to both poles.

• Centromeres split, separating chromatids.
• Chromatids migrate to opposite poles.

Key features of telophase are:

• Chromosomes assemble around opposite spindle poles, losing their individual identity.
• A nuclear envelope forms around the chromosome clusters at each pole, resulting in the formation of two daughter nuclei.
• Components like the nucleolus, Golgi complex, and endoplasmic reticulum (ER) reassemble.

What is Meiosis?

Phases of Meiosis I

• Leptotene marks the initial stage where chromosomes gradually become visible under the light microscope while continuing to compact.
• In Zygotene, homologous chromosomes start pairing together through a process known as synapsis, forming structures called bivalents or tetrads, helped by the development of a synaptonemal complex.
• Pachytene follows, characterized by the distinct appearance of four chromatids within each bivalent and the initiation of crossing over at specific points known as recombination nodules, facilitated by the enzyme recombinase.
• During Diplotene, the dissolution of the synaptonemal complex occurs, and chiasmata, the visible manifestations of crossover points, become more pronounced.
• Diakinesis marks the final stage of prophase I, characterized by the terminalization of chiasmata, full condensation of chromosomes, and the assembly of the meiotic spindle, signaling the transition to metaphase.

Phases of Meiosis II

Benefits of CBSE Class 11 Biology Notes Chapter 10

• Chapter 10 Cell Cycle and Cell Division notes offers a complete overview of the topic, covering all essential concepts and stages involved in cell cycle and cell division.
• The notes provided clear and concise explanations of complex biological processes, making it easier for students to understand the concepts of cell division.
• The notes provide information in a systematic manner that aids in better understanding and retention of the material.