Cell Reproduction Grade 12 PDF

Cell reproduction Chromosomes Grade 12 Quarter 1topics  - Cell reproduction  - chromosomes  -Cell division  -the cell cycle  -Mitosis  -Meiosis  -Formation of gametes  -Sexual and asexual reproduction  -Genetics  -Mendel  -DNA  DNA replication  _R...

Cell reproduction Chromosomes Grade 12 Quarter 1topics  - Cell reproduction  - chromosomes  -Cell division  -the cell cycle  -Mitosis  -Meiosis  -Formation of gametes  -Sexual and asexual reproduction  -Genetics  -Mendel  -DNA  DNA replication  _RNA Structure of chromosome What are Chromosomes?  Chromosomes are thread-like structures found in the nucleus of cells  Composed of DNA and proteins  Carry genetic information that determines traits and functions  Humans have 23 pairs of chromosomes (46 total)  Definition: Compact packages of genes and other DNA in cells DNA DNA is a long thin molecule that stores genetic information.  DNA in a human cell is estimated to consist of six billion pairs of nucleotides Structure of Chromosomes  Chromosomes have two main parts:  Chromatids: identical copies of genetic material  Centromere: where chromatids join Importance of Chromosomes  1.Store and protect genetic material  2. Ensure accurate distribution of DNA during cell division  3. Determine inheritance of traits  4. Essential for proper growth, development, and function of organisms Question time !  1. What is the primary function of chromosomes? a. To produce energy for the cell b. To store and transmit genetic information c. To synthesize proteins d. To break down cellular waste  2. Which of the following best describes the structure of DNA? a. A single-stranded helix b. A triple-stranded molecule c. A double-helix structure d. A circular plasmid  3. What is the name of the protein-DNA complex that makes up chromosomes? a. Ribosome b. Nucleotide c. Chromatin d. Centromere d. Amino acid  4. How many chromosomes are typically found in a human somatic cell? a. 23 b. 46 c. 22 d. 44  5. Which of the following is NOT a component of a nucleotide in DNA? a. Phosphate group b. Deoxyribose sugar c. Nitrogenous base 17/9/2024  DNA in eukaryotic cells wraps tightly around proteins called histones  Histones : help maintain the shape of chromosomes and aid in the tight packing of DNA.  Non histone proteins : are generally involved in controlling the activity of specific regions of the DNA  -chromatid form as the DNA makes a copy of it self before cell division  When cell divides ,each of new cell receive one chromatid from each chromosome Histones & non histones  Centromere are especially important for the movement of chromosomes during cell division. Chromosomes numbers  Human and animal chromosomes are categorized as either sex chromosomes or autosomes.  Sex chromosomes: are chromosomes that determines the sex of an organism , and they may also carry genes for other characteristics in humans  Sex chromosomes are X or Y  Normal females have two X chromosomes  Normal males have an X and a Y chromosomes  Humans 46 chromosomes = 23 pairs Numbers of chromosomes  Cat = 32  Dog = 78  Horse = 64  Fruit fly = 8 Question time !  1. What is the main difference between haploid and diploid cells? a. Haploid cells have twice the number of chromosomes as diploid cells b. Diploid cells have twice the number of chromosomes as haploid cells c. Haploid cells only exist in plants, while diploid cells exist in animals d. There is no difference between haploid and diploid cells  2. In humans, which of the following cell types is haploid? a. Skin cells b. Liver cells c. Gametes (sperm and egg cells) d. Muscle cells  3. If a diploid cell of an organism has 2424 chromosomes, how many chromosomes will be present in its haploid cells? a. 4848 b. 2424 c. 1212 d. 66  4. Which of the following statements about chromosome numbers is correct? a. All organisms have the same number of chromosomes in their diploid cells b. The number of chromosomes in a cell determines the complexity of an organism c. Haploid cells always have an odd number of chromosomes d. The haploid number is typically represented as n, while the diploid number is 2n Answers 1. b 2. c 3. c 4. d Cell Division  Cell division : is the process by which cells produce offspring  Cell division in prokaryotic :  Binary fission :is the division of a prokaryotic cell into two offspring cells.  Binary fission consists of three general stages  The Cell Cycle: Phases  Interphase: G1, S, and G2 phases  G1: Cell growth and preparation  S: DNA replication  G2: Further growth and preparation for division  M phase: Mitosis (nuclear division) and Cytokinesis (cell division) Binary fission  The cell cycle : is the repeating set of events that make up the life of a cell.  Cell division : is one phase of the cell cycle  The time between cell division is called interphase  During cell division , the chromosomes and cytoplasm are equally divided between two offspring cells.  Cell division consist of mitosis and cytokinesis , during mitosis or M phase the nucleus of a cell divides  Cytokinesis : is the division of the cytoplasm of the cell  Mitosis : is the division of the nucleus , which occurs during cell division.  Mitosis : is a continuous process that id divided into four phases.  -prophase  -metaphase  -anaphase  -Telophase  Mitosis is a process of cell division in eukaryotic cells Results in the production of two identical daughter cells Crucial for growth, repair, and asexual reproduction Occurs in somatic (body) cells, not reproductive cells Maintains the same number of chromosomes in daughter cells Stages of mitosis Meiosis