Students can go through AP Inter 1st Year Botany Notes 11th Lesson Cell Cycle and Cell Division will help students in revising the entire concepts quickly.
AP Inter 1st Year Botany Notes 11th Lesson Cell Cycle and Cell Division
→ Cell theory states that, cells arise from pre existing cells.
→ Sexually Reproducing organism starts its life cycle from single called Zygote.
→ The stages through which a cell passes from one division to the next is called the cell cycle.
→ Cell cycle is divided into Two phases called
- Interphase a period of preparation for cell Division and
- Mitosis (M Phase) – the actual period of cell division.
→ Interphase is furthur subdivided into G11 S and G2 phages.
→ G1 phase is the period when the cell grows and f carries out normal metabolism.
→ S phase marks the phase of DNA replication and chromosome Duplication.
→ G2 phase is the period of cytoplasmic growth.
→ Mitosis or M phase is divided into four phases namely prophase. Metaphase, Anaphase and Telophase.
→ Chromosomal condensation occurs during prophase, The centrioles when present move to opposite poles, The nuclear envelope and nucleolus disappears.
→ Metaphase is marked by alignment of chromosomes I at the equatorial plate.
→ The centromeres divide and the chromatids move to Two opposite poles during anaphase.
→ The chromosomal elongation starts, nuclear envelope and nucleolus reappears during Telophase.
→ Cytoplasmic division is called cytokinesis.
→ Meiosis occurs in the diploid cells. It is called reductional division in which chromosomal number is reduced to half while making the gametes.
→ Meiosis is divided into two phages namely Meiosis I and Meiosis II.
→ Meiosis I is divided into prophase I, Metaphase I Anaphase I and Telophase I.
→ Prophase I is long lasting phase and is sub divided into Leptotene, Zygotene, Pachytene, Diplotene and diakinesis.
→ Crossing over occurs in Pachytene sub phase.
→ Meiosis II is similar to Mitosis and has Prophase II.
Metaphase II, Anaphase II and Telophase II.
→ At the end of Meiosis four haploid cells are formed.
→ Bivalent : A pair of homologous chromosomes in synopsis.
→ Cell Cycle : Cyclic sequence of events by which the cell duplicates its genome and eventually divides.
→ Cell plate : Precursor of cell wall, formed during cytokinesis in plant cells.
→ Chiasmata : X-shaped structures formed as a consequence of crossing over.
→ Chromatid : Longitudinal half of a metaphase chromosome.
→ Cytokinesis : Division of the cytoplasm.
→ Diplotene : Stage of Prophase I of meiosis where paired chromosomes start to separate.
→ Interphase : A preparatory stage which intervenes between two successive divisions.
→ Karyokinesis : Division of the nucleus.
→ Pachytene : Thick thread stage in which exchange of chromosomal material between homo- logues takes place.
→ Quiscent stage (G0) : An inactive stage of the cell cycle for cells that no longer divide.
→ Synaptonemal complex : A proteinaceous complex in which the homologous chromosomes are held together during prophase-I of meiosis.
→ Cell cycle is the life of cycle of a cell, which covers its birth, growth and cell division.
→ Cell division is the process by which a parent cell divides into two or more daughter cells.
→ Cell cycle is divided into two phases (i) Inter phase (ii) Mitosis
→ Interphase is a period of preparation for cell division.
→ Mitosis (M phase) is the actual period of cell division.
→ Inter phase is subdivided into G1 phase, S phase and G2 phase. [IPE]
→ G1 phase is the period when the cell grows and carries out normal metabolism. [IPE]
→ In S phase, replication of DNA and duplication of chromosomes occur. [IPE]
→ G2 phase is the period of Cytoplasmic growth. [IPE]
→ Mitosis is divided into Prophase, Metaphase, Anaphase and Telophase. [IPE]
→ Chromosome condensation occurs during Prophase. [IPE]
→ The Prophase I is longer and more complex when compared to prophase of mitosis. [IPE]
→ It is sub divided as (i) Leptotene (ii) Zygotene (iii) Pachytene (iv) Diplotene (v) Diakinesis.
→ Metaphase is marked by the alignment of chromosomes at equatorial plate. [IPE]
→ During Anaphase centromere divides and chromatids start moving towards opposite poles.
→ Once chromatids reach the poles, chromosomal elongation starts, nucleolus and nuclear membrane reappear. This is called Telophase.
→ During cell growth, DNA synthesis takes place on S-phase. [NEET-2016]
→ In meiosis crossing over is initiated at pachytene. [NEET-2016]
→ Spindle fibres attach on to kinetochore of the chromosome. [NEET-2016]
→ The enzyme recombinase is required at the stage of meiosis is Pachytene. [NEET-2014]
→ In ‘S’ phase of the cell cycle amount of DNA doubles in each cell. [NEET-2014]
→ The complex formed by a pair of synapsed homologous chromosomes is called bivalent. [NEET-2013]
→ During gamete formation, the enzyme recombinase participates during Prophase-I. [2012 PMT]
→ During mitosis, ER and nucleolus begin to disappear at early prophase. [2010 PMT]
→ Synapsis occurs between two homologous chromosomes. [2009 PMT]
→ Correct sequence of Phases of Cell cycle is G1 → S → G2 → M [NEET-2019]
→ Cells in G0 phase exit the cell cycle. [NEET-2019]
→ The centriole undergoes duplication during Prophase. [NEET-2021]
→ Anaphase II involves division of centromere. [NEET-2021]