2.6 Cell division

• What type of cell does meiosis start with?

  Diploid cell
• How many haploid gametes are produced by meiosis?

  Four haploid gametes
• What is a key idea about meiosis?

  It involves two rounds of nuclear division
• What happens during meiosis 1?

  Homologous chromosomes are separated
• What happens during meiosis 2?

  Sister chromatids are separated
• What occurs during interphase before meiosis?

  The cell copies chromosomes and organelles
• What happens to chromosomes during prophase 1?

  They condense and become visible
• What do homologous chromosomes form during prophase 1?

  Bivalent
• What is crossing over?

  Exchanging alleles between homologous chromosomes
• What happens to the nuclear membrane during prophase 1?

  It breaks down
• What is the role of spindle fibers during meiosis?

  They help separate chromosomes
• What happens during anaphase 1?

  Homologous chromosomes move towards opposite poles
• What occurs during telophase 1?

  Nuclear membranes reform and chromosomes uncoil
• What type of cells are produced after meiosis 1?

  Haploid cells
• What is the first stage of meiosis 2?

  Prophase 2
• What happens during metaphase 2?

  Chromosomes line up on the equator
• What occurs during anaphase 2?

  Centromeres divide and chromatids move apart
• What happens during telophase 2?

  Nuclear membranes reform and chromosomes uncoil
• How many haploid cells are produced at the end of meiosis?

  Four haploid cells
• Why is meiosis called reduction division?

  Because the chromosome number halves
• What is a major source of genetic variation in meiosis?

  Crossing over
• What is independent assortment?

  Random distribution of maternal and paternal chromosomes
• How many chromosome pairs do human cells have?

  23 chromosome pairs
• How many genetically different gametes can be produced by independent assortment?

  $2^n$ where $n$ is chromosome pairs
• What is the number of genetically different gametes for humans?

  Over 8 million
• What introduces additional genetic variation during fertilization?

  Random fusion of male and female gametes
• What are the two main ways meiosis produces genetic variation?

  • Crossing over
  • Independent assortment of chromosomes
• What are the stages of meiosis?

  1. Meiosis 1:

  • Prophase 1
  • Metaphase 1
  • Anaphase 1
  • Telophase 1

  1. Meiosis 2:

  • Prophase 2
  • Metaphase 2
  • Anaphase 2
  • Telophase 2
• What happens to chromosomes during cytokinesis in meiosis?

  • The cell divides into two haploid cells
  • Each cell contains individual chromosomes
• What are specialized cells that carry oxygen in the blood?

  Erythrocytes
• What is the primary function of erythrocytes?

  To carry oxygen in the blood
• What type of white blood cell is a neutrophil?

  A type of white blood cell
• What do neutrophils do?

  Engulf foreign cells and pathogens
• What do granules in neutrophils contain?

  Digestive enzymes
• What is the role of digestive enzymes in neutrophils?

  To hydrolyze pathogens
• What is the function of sperm cells?

  Deliver genetic information to the ovum
• What structure helps sperm cells swim?

  Flagellum
• What is the function of mitochondria in sperm cells?

  To supply energy for swimming
• What does the acrosome of sperm cells contain?

  Digestive enzymes
• What is the purpose of the enzymes in the acrosome?

  To digest protective layers around the ovum