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Understanding Meiosis: The Key to Genetic Diversity in Humans

Meiosis is a crucial process in human reproduction, resulting in the formation of gametes (egg and sperm) and ensuring genetic diversity. It involves two division stages that produce four non-identical haploid cells from one diploid cell, halving the chromosome number from 46 to 23. This intricate process includes important phases such as Prophase I, where crossing-over occurs, enhancing genetic variation. Understanding meiosis is essential for grasping how traits are inherited and why genetic diversity is vital for evolution.

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Understanding Meiosis: The Key to Genetic Diversity in Humans

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  1. Meiosis By: Aya El-GhajijiIFY

  2. Meiosis • Human body cells have 46 chromosomes. • Each parent contributes 23 chromosomes. • It produces sex cells (gametes): egg and sperm. • One cell becomes 4 NON-IDENTICLE cells

  3. Genetic Terms • Chromosome • Chromatin • Chromatid • Sister chromatids • Homologous pair

  4. Chromosome • Structure of DNA in nucleus providing genetic information.

  5. chromatin • The material of which chromosomes are made = DNA + histone proteins.

  6. Chromatid • Chromosome copy. One pair of replicated chromosomes found during Interphase.

  7. Sister chromatids • Identical copies of one chromosome.

  8. Homologous pair • Pair of chromosome each coding for the same characteristics originally from the male parent and one from the female parent.

  9. WHY DO WE NEED MIOSIS? • To maintain the same number of chromosomes from generation to generation. • Human gametes contain 23 chromosomes. • A cell with n chromosomes is called a haploid cell. • A cell that contains 2n chromosomes is called a diploid cell.

  10. Meiosis

  11. Meiosis I • Interphase • Chromosomes replicate • Centriole pair replicates. Interphase

  12. Meiosis I • Prophase I • Chromatin condense • Pairing of homologous chromosomes • Each chromosome consists of two chromatids. • The nuclear membrane breaks down. • Spindles form.

  13. Meiosis I • Prophase I • Crossing over produces exchange of genetic information. • Crossing over—chromosomal segments are exchanged between a pair of homologous chromosomes.

  14. Meiosis I • Metaphase I • Homologous chromosomes line up at the equator. • Chromosome centromeres attach to spindle fibers.

  15. Meiosis I • Anaphase I • Homologous chromosomes separate and move to opposite poles of the cell.

  16. Meiosis I • Telophase I • The spindles break down. • The cell divides. • Cytokinesis

  17. Meiosis II • Prophase II • Spindle apparatus forms • chromosomes condense.

  18. Meiosis II • Metaphase II • A haploid number of chromosomes line up at the equator.

  19. Meiosis II • Anaphase II The sister chromatids are pulled apart at the centromere by spindle fibers and move toward the opposite poles of the cell.

  20. Meiosis II • Telophase II • The chromosomes reach the poles, and the nuclear membrane and nuclei reform.

  21. Meiosis II • Cytokinesis results in four haploid cells, each with n number of chromosomes.

  22. The Importance Of Meiosis It results in genetic variation

  23. Meiosis http://www.youtube.com/watch?v=kVMb4Js99tA

  24. Quiz • A human cell containing 22 autosomes and a Y chromosome is • A zygote • A sperm cell • An ovum

  25. Quiz • Homologous chromosomes segregate toward opposite poles of a dividing cell during • Mitosis • Meiosis I • Meiosis II

  26. Bibliography • BAKER, M., INDGE, B., & ROWLAND, M. (2001). Further studies in biology. London, Hodder & Stoughton. • CAMPBELL, N. A. (1996). Biology. Menlo Park, Calif, Benjamin/Cummings Pub. Co. • Llopis-Garcia, R., (2012) Meiosis Notes. City of Bath College. • PARSONS, R. (2009). AS & A2 Biology: complte revision guide and practice : exam board AQA. Kirkby-in-Furness, Coordination Group. • TOOLE, G., & TOOLE, S. (2008). AQA biology AS. Cheltenham, Nelson Thornes.

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