Cell division 2 Meiosis
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Meiosis is a type of cell division that produces gametes or sex cells with half the number of chromosomes as the original parent cell. It involves two divisions and results in four daughter cells each with a single set of chromosomes. This ensures that offspring will receive one set of chromosomes from each parent, maintaining the chromosome number from generation to generation. The key phases and events of meiosis include homologous chromosome pairing, crossing over, independent assortment of chromosomes into new cells, and two divisions that ultimately produce four haploid cells or gametes.
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Cell division occurs through mitosis and meiosis. Mitosis produces two identical daughter cells and is used for growth and repair in multicellular organisms. It has five stages: interphase, prophase, metaphase, anaphase, and telophase. During interphase, the cell grows and duplicates its DNA. In prophase, chromosomes condense. Then in metaphase, chromosomes align at the center before separating in anaphase and moving to opposite poles. Finally, in telophase, two identical daughter nuclei form and cytokinesis divides the cytoplasm, completing cell division.
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This document provides an overview of meiosis. It begins by defining important vocabulary like diploid, haploid, fertilization and zygote. It then explains that meiosis occurs in sexual reproduction and results in four haploid daughter cells that can mature into gametes. The document outlines the two parts of meiosis - Meiosis I and Meiosis II. It provides details on the phases of each part, including prophase, metaphase, anaphase and telophase. The document also discusses topics like homologous chromosomes, crossing over, sex chromosomes, cytokinesis, spermatogenesis, and conditions caused by non-disjunction like Down's syndrome. In summary, it is a thorough explanation of the process of
Meiosis
This document summarizes the key stages and purpose of meiosis. Meiosis involves two cell divisions that result in four haploid daughter cells, each with half the number of chromosomes as the original cell. This ensures genetic variation in offspring. The stages include prophase I with synapsis and crossing over, metaphase I and II, anaphase I and II, telophase I and II, and cytokinesis. Meiosis reduces the chromosome number through homologous chromosome separation in meiosis I and sister chromatid separation in meiosis II, allowing for genetic recombination and independent assortment of maternal and paternal chromosomes in gametes. Errors can result in conditions like Down syndrome.
Ths general biology unit 4 heredity reproduction and meiosis notes_v1516
Meiosis is the process of cell division that produces gametes (sperm and egg cells) for sexual reproduction. It involves two cell divisions that result in four haploid cells, each with half the number of chromosomes as the original cell. This ensures that offspring have a full set of chromosomes when fertilization occurs. The main features of meiosis include homologous chromosome pairing, crossing over to increase genetic variation, and independent assortment of chromosomes into daughter cells through the first and second meiotic divisions. Errors in meiosis can result in gametes with an abnormal number of chromosomes, causing genetic disorders.
Mitosis meiosis mine
Heredity involves the transmission of genetic information from parents to offspring. Genetics is the study of heredity. Mitosis and meiosis are the two types of cell division involved in heredity. Mitosis produces genetically identical cells for growth and tissue repair, while meiosis produces haploid gametes through two divisions resulting in four genetically distinct cells. Meiosis ensures genetic diversity and integrity in sexually reproducing organisms.
Genetics Notes
1. Somatic cells make up the body and undergo mitosis, while gamete cells (sperm and egg) undergo meiosis and are haploid.
2. Chromosomes contain DNA and come in pairs, with one chromosome from each parent. Autosomes are non-sex chromosomes 1-22, while sex chromosomes are X and Y and determine gender.
3. Asexual reproduction involves one parent and produces genetically identical offspring through mitosis, while sexual reproduction combines gametes through fertilization producing offspring with a mix of parental genes.
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Ths general biology unit 4 heredity reproduction and meiosis notes_v1516
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Cell division 2 Meiosis
- 1. Cell Division 2: Meiosis ppt. by Robin D. Seamon 1
- 2. MEIOSIS 2
- 3. sexual reproduction: • eukaryotic reproductive adaptation • advantage: mixing of genes from two parents to create more genetic diversity in the offspring • not being identical to the parent is advantageous for a species… if an outside stimulus is introduced that the species is unable to withstand, there is a greater chance that at least some members of the species will have a variation or gene combination that can make it 3
- 4. METHOD meiosis- a type of cell division where the cell divides twice • this results in four daughter cells each with half the number of chromosomes of the parent cell • produce gametes and plant spores. WHY HALF? 4
- 5. Consider humans: Humans have 23 PAIRS of chromosomes (or 46 total chromosomes) If a female cell of 46 chromosomes combined with 46 chromosomes of a male cell, the resulting offspring would have TOO MANY- 92 chromosomes! Therefore, a different cell division process must occur for the production of sex cells: meiosis. 5
- 6. XX – female XY- male6 HUMAN CHROMOSOME Karyotype one set from mom one set from dad autosomes: 22 pairs of body cells sex cells: X or Y chromosomes homologous pair 1
- 7. gamete- sex cell • egg or ova- female gamete • sperm- male gamete 7
- 8. 8 HAPLOID sex cells are haploid- have half the number of chromosomes DIPLOID- two sets of chromosomes
- 9. 9
- 10. 10 Meiosis 1 begins with ONE DIPLOID cell (2n) Meiosis 2 ends with FOUR HAPLOID cells (n) 2n = 46 n = 23
- 11. 11 MEIOSIS PHASES Interphase 1- chromosomes replicate Prophase 1 Metaphase 1 Anaphase 1 Telophase 1 Cytokinesis 1 Interphase 2 BRIEF Prophase 2 Metaphase 2 Anaphase 2 Telophase 2 Cytokinesis 2 *THIS ONLY HAPPENS ONCE! “preparing” “middle” “away” “two” = 4 haploid cells
- 14. 14
- 15. 15 MEIOSIS 1: Interphase 1- cell replicates DNA • (This will not happen again in the second division!) • prepares for cell division
- 16. 16 MEIOSIS 1: Prophase 1- • homologous chromosomes pair up • make a tetrad • crossing over- non-sister chromosomes exchange genetic pieces of chromosome • results in NEW COMBINATIONS of genes on the chromosomes
- 17. 17 Crossing over of Chromosomes
- 19. 19 MEIOSIS 1: Metaphase 1- • new tetrads move to the middle along spindle fibers
- 20. 20 MEIOSIS 1: Anaphase 1- • homologous chromosomes separate • independent assortment: each new cell randomly gets ONE chromosome from the homologous pair ***Genetic variation***
- 21. 21 MEIOSIS 1: Telophase 1- • spindle breaks down • cytoplasm divides • each cell will have HALF the genetic information because it only has ONE CHROMOSOME from each homologous pair
- 22. 22 MEIOSIS 1: Cytokinesis 1- • 2 new cells
- 23. 23 MEIOSIS 2: *NO COPYING or CROSS-OVER OF DNA Prophase 2: preparing for division Metaphase 2: moving to the middle Prophase 2 Metaphase 2
- 24. 24 MEIOSIS 2: Anaphase 2: moving away Telophase 2: two cells Anaphase 2 Telophase 2
- 25. MEIOSIS 2: Cytokinesis 2: 4 haploid cells are produced • 4 spermatids: gametes produced in the testes of males • one egg and 3 polar bodies: gametes produced in the ovaries of females (polar bodies degenerated & are not fertilized) 25
- 26. 26
- 27. 27
- 28. 28