Download
chapter 8 3 n.
Skip this Video
Loading SlideShow in 5 Seconds..
Chapter 8.3 PowerPoint Presentation
Download Presentation
Chapter 8.3

Chapter 8.3

681 Vues Download Presentation
Télécharger la présentation

Chapter 8.3

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. Chapter 8.3 Meiosis

  2. Types of Reproduction • Asexual reproduction • Produce offspring with only ONE parent • “babies” are identical to parent • Sexual reproduction • Produce offspring by meiosis and the joining of the sperm and egg • “babies” are NOT identical to parents

  3. Meiosis • New cells have half the number of chromosomes • Gametes • Reproductive cells (sperm and egg)

  4. Key Points • Meiosis must happen so when the sperm and egg join to create a new organism, it has the correct number of chromosomes. • Examples: • Human = 46 • Egg = 23 • Sperm = 23 • Egg + Sperm = baby • 23 + 23 = 46

  5. Meiosis I. (very similar to mitosis) • Prophase I. • DNA coils into chromosomes • Each chromosome lines up with its homologue (the similar chromosomes) • Synapsis: pairing of homologous chromosomes • Each pair is called a tetrad • Crossing-over: may occur where pieces of one chromosome break off and attach to the other chromosome  genetic recombination

  6. Metaphase I. • Tetrads line up along the middle of the cell

  7. Anaphase I. • Each homologous chromosome of each tetrad moves to opposite ends of the cell

  8. Telophase I. • Cell divides creating 2 new cells each with a haploid number of chromosomes (1/2 the original number of chromosomes, but 2 copies of each)