Meiosis

• A cell with two pairs of each set of chromosomes is called a diploid.
• The number of chromosomes in the nucleus of a human body cell is 46.
• Each pair of homologous chromosomes contains one maternal chromosome and one paternal chromosome.
• A cell with only one set of chromosomes is called haploid.
• Sperm and egg cells are called gametes.
• A fertilized egg is called a zygote.
• A type of cell division that results in diploid cell are mitosis. Each identical cell have the same number of chromosomes as the original cell.
• When a sperm and egg combine, it is called fertilization.
• During prophase I of meiosis, chromosome pairs form a tetrad in a process called recombination.
• How many daughter cells are created at the end of meiosis I?

  2
• How many daughter cells are created at the end of meiosis II?

  4
• During meiosis, chromosomes will split into daughter cells randomly, make each gamete unique. What is this called?

  Genetic Variability
• The process by which sperm is made is called spermatogenesis
• The process by which eggs are made is called oogenesis.
• In what two ways does meiosis produce genetic variation?

  Independent assortment and crossing over(recombination).
• What are key events that occur in meiosis I?

  Homologous chromosome pairing, crossover exchanges, sister chromatids remaining attached during anaphase, and DNA replicates only once during meiosis.
• Characteristics in Meiosis that Differ from Mitosis: 1. It has two divisions, the chromosome number is halved, the process "crossing over" occurs, it is associated with sexual reproduction, it produces gametes, recombination occurs, and four daughter cells are produced.
• At the end of meiosis, 4 different cells are produced. (genetic variability)
• Nondisjunction: can lead to extra or missing chromosomes.
• Example of non disjunction: Down Syndrome