Meiosis

• What is the purpose of meiosis?

  To produce haploid gametes for reproduction
• What happens during meiosis?

  Homologous chromosomes separate to form gametes
• How does meiosis create genetic variation?

  Through crossing over and independent assortment
• How can a mutation of a gene affect enzyme production?

  It can lead to a non-functional enzyme
• What is a mutation?

  An incorrect sequence of bases in DNA
• What is a chromosome?

  Thread-like structures in the nucleus
• What is a chromatid?

  One of two identical halves of a chromosome
• What is a centromere?

  A constricted region of a chromosome
• What are spindle fibers?

  Filaments that form the mitotic spindle
• What is a bivalent?

  Two homologous chromosomes paired together
• What does haploid mean?

  Cells with one complete set of chromosomes
• What does diploid mean?

  Cells with two complete sets of chromosomes
• How many chromosomes do diploid human cells have?

  46 chromosomes (23 pairs)
• What is the outcome of meiosis?

  Four haploid daughter cells are produced
• Why is it important to halve the number of chromosomes during meiosis?

  To maintain a constant chromosome number in adults
• What happens to homologous chromosomes during meiosis?

  They separate into different gametes
• Where does meiosis occur?

  In the sex organs (ovaries/testes)
• What is the role of crossing over in meiosis?

  To exchange genetic material between chromatids
• What is independent assortment?

  Random separation of maternal and paternal chromosomes
• When does independent assortment occur?

  During metaphase I of meiosis
• What is the significance of random fertilization?

  It increases genetic diversity in offspring
• What is a zygote?

  A fertilized egg formed from two gametes
• What is the relationship between genotype and phenotype?

  Genotype plus environment equals phenotype
• What are the three sources of genetic variation in sexual reproduction?

  Independent assortment, crossing over, random fertilization
• What happens to chromosomes during prophase I of meiosis?

  Chromosomes condense and homologous pairs form
• What occurs during metaphase I of meiosis?

  Bivalents line up along the equator
• What happens during anaphase I of meiosis?

  Homologous chromosomes are pulled to opposite poles
• What is the outcome of telophase I in meiosis?

  The cell divides by cytokinesis
• What happens during prophase II of meiosis?

  Spindle forms at right angles to the original spindle
• What occurs during metaphase II of meiosis?

  Chromosomes line up at the equator
• What happens during anaphase II of meiosis?

  Centromeres divide and chromatids separate
• What is the final outcome of meiosis?

  Four haploid cells are produced
• What is the significance of crossing over during meiosis?

  It allows mixing of maternal and paternal alleles
• What is the role of cytokinesis in meiosis?

  It divides the cytoplasm into daughter cells
• How does meiosis contribute to evolution?

  By allowing genetic variation in populations
• What is the advantage of genetic variation to a species?

  It allows adaptation to changing environments
• What is the effect of silent mutations?

  They have no phenotypic effect
• What is the relationship between genotype and environment?

  Genotype interacts with environment to form phenotype
• What are the stages of meiosis?

  1. Interphase: Chromosomes replicate
  2. Meiosis I:

  • Prophase I: Homologous pairs form bivalents, crossing over occurs
  • Metaphase I: Bivalents line up at the equator
  • Anaphase I: Homologous chromosomes separate
  • Telophase I: Cell divides by cytokinesis

  1. Meiosis II:

  • Prophase II: Spindle forms
  • Metaphase II: Chromosomes line up at the equator
  • Anaphase II: Centromeres divide and chromatids separate
  • Telophase II: Cells split via cytokinesis
• What are the sources of genetic variation in sexual reproduction?

  1. Independent assortment
  2. Crossing over
  3. Random fertilization