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Meiosis

Meiosis. Sex cell production. Meiosis - Sex Cell Reproduction. Sex cells have ½ the number of chromosomes Humans have 46 chromosomes So human sex cells have how many chromosomes? 23 When sex cells combine the offspring will have a full set of chromosomes. Requires two parents

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Meiosis

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  1. Meiosis Sex cell production

  2. Meiosis - Sex Cell Reproduction • Sex cells have ½ the number of chromosomes • Humans have 46 chromosomes • So human sex cells have how many chromosomes? • 23 • When sex cells combine the offspring will have a full set of chromosomes • Requires two parents • Parent cells produce sex cells • Male (sperm) • Females (egg)

  3. Sexual Reproduction • Advantages of sexual reproduction • Chromosomes from 2 parents • offspring are different than the parent • Offspring are likely more adaptable • Different from asexual reproduction which ALWAYS produces offspring that are the SAME.

  4. Homologous Chromosomes • Chromosomes that carry the same set of instructions. • One from mother and one from father • Remember – these replicate during interphase!

  5. Meiosis • Produces sex cells and • Parent cells divide twice producing 4 daughter cells Growing quadruplets • Daughter cells (sex cells) have ½ the number of chromosomes as the parent cell

  6. Meiosis occurs in two steps….. Meiosis I Contains all the steps of mitosis Is like mitosis except… • Homologous chromosomes pair up • Sister chromatids don’t separate • Produces TWO cells

  7. Meiosis II Contains all steps of mitosis Is like mitosis except: • No DNA replication • 4 daughter cells with ½ number of chromosomes as parent

  8. Additional Vocabulary • Diploid (2n) – full set of chromosomes • Parent cell • Haploid (n) – half a set of chromosomes • Daughter cells

  9. Sperm Cells Sex Cells Egg Cells

  10. http://www.mwit.ac.th/~bio/assets/meiosis%5B1%5D.swf

  11. Mitosis & Meiosis on the Table • Objective: Discover critical differences between mitosis and meiosis, and the main functions of meiosis. • Assumptions: copy from handout • Table: Distinguishing features • Summary: Copy from handout • Questions: • What are the 2 main functions of meiosis? • If you were to model an organism with six chromosomes how many more pipe cleaners will you need? Will you need to use a third color? Why or why not? • Adder’s fern has 1,400 chromosomes. How many chromosomes do its sex cells have?

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