Genetics Lecture 2 PDF
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Mansoura National University
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This document provides lecture notes on genetics, focusing specifically on cell division, mitosis, and meiosis. It details the stages of these processes, including diagrams for visual clarity. The summary also highlights the differences in cytokinesis between animal and plant cells.
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# Genetics - Lecture 2 ## Cell Cycle * **Growth** - Occurs during Interphase * **Cell Division** - Mitosis (4 stages) **Diagram:** | Stage | Description | |---|---| | G<sub>1</sub> | Metabolic Activity, to Produce ATP, Pre-replication stage | | S | DNA synthesis (<br> DNA Replication) | | G<sub...
# Genetics - Lecture 2 ## Cell Cycle * **Growth** - Occurs during Interphase * **Cell Division** - Mitosis (4 stages) **Diagram:** | Stage | Description | |---|---| | G<sub>1</sub> | Metabolic Activity, to Produce ATP, Pre-replication stage | | S | DNA synthesis (<br> DNA Replication) | | G<sub>2</sub> | Metabolic Activity, Post-replication Stage | ### Cell Division * **Strasburger discovered cell division in plant cells.** * **Flemming discovered cell division in animal cells.** * **2 types of cell division:** * Mitosis * Meiosis ## Mitosis * **Occurs in somatic cells** * **Produces two cells** * **Each cell contains the same chromosome number** * **One division with four stages:** * Prophase * Metaphase * Anaphase * Telophase ## Meiosis * **Occurs in reproductive cells during gametes formation** * **Produces 4 cells** * **Each cell contains half the chromosome number** * **Two divisions:** * Meiosis I - First meiotic division * Meiosis II - Second meiotic division * Each division has 4 stages ## Mitosis (Nuclear Division - Cytokinesis) **Diagram:** | Stage | Description | |---|---| | Interphase | Nuclear envelope, nucleolus, chromatin net, nuclear sap | | Prophase | 1. Nuclear envelope disappears <br> 2. Nucleolus disappear<br> 3. Contraction of chromatin net to chromosomes | | Metaphase | 1. Arrangement of chromosomes at the equator <br> 2. Centromere division<br> 3. Appearance of spindle fibers on the sides | | Anaphase | 1. Extension of spindle fibers to get attached to centromeres <br> 2. Pulling of chromatins to up and down | | Telophase | 1. Reappearance of nuclear envelope <br> 2. Reappearance of nucleolus <br> 3. Replication of DNA <br> 4. Chromatin became chromosomes | ## Cytokinesis **The 4-stage Nuclear Division and then Cytoplasmic Division (Cytokinesis)** ### In animal cells: * Cytoplasmic division is by furrowing because of the flexibility of the plasma membrane. ### In plant cells: * Cytoplasmic division is by middle lamella because of the presence of the cell wall (rigid). **Diagram:** * Animal cell - furrowing * Plant cell - two cells, cellulose, pectin
