chapter 10 - meiosis

• What distinguishes living organisms?

  Their ability to reproduce their own kind
• What is genetics?

  The scientific study of heredity and variation
• What is heredity?

  The transmission of traits from one generation to the next
• How is variation demonstrated in offspring?

  By the differences in appearance that offspring show from parents and siblings
• What will be learned in this genetics overview?

  • Genetics on the level of organism, cell, and molecule
  • How genetics is revolutionizing medicine and agriculture
  • Ethical questions arising from DNA manipulation
  • Development from a single cell (the fertilized egg)
• What do children inherit from their parents?

  Genes
• What do genes program in an organism?

  Specific traits that emerge during development
• What are genes made up of?

  Segments of DNA
• What is a locus?

  A specific location of a gene on a chromosome
• How are genes passed to the next generation?

  Through reproductive cells called gametes
• How many chromosomes do humans have in their somatic cells?

  46 chromosomes
• How many chromosomes do gametes have?

  23 chromosomes
• What is asexual reproduction?

  One parent produces genetically identical offspring by mitosis
• When does asexual reproduction result in non-identical offspring?

  If a mutation occurs
• What is a clone?

  A group of genetically identical individuals from the same parent
• What is sexual reproduction?

  Two parents give rise to offspring with unique combinations of genes
• What are human somatic cells composed of?

  • 23 pairs of chromosomes
  • 46 total chromosomes
• What is a karyotype?

  An ordered display of the pairs of chromosomes from a cell
• What are homologous chromosomes?

  Two chromosomes in each pair that are the same length and carry genes controlling the same inherited characters

  
• What determines the biological sex of an individual?

  The sex chromosomes, X and Y
• What is the diploid number for humans?

  46 (2n = 46)
• What is a haploid cell?

  A cell that contains a single set of chromosomes
• How many chromosomes does a human gamete contain?

  23 chromosomes
• What is fertilization?

  The union of gametes (the sperm and the egg)

  
• What is a zygote?

  The fertilized egg that has one set of chromosomes from each parent
• What do somatic cells produce by mitosis?

  Somatic cells
• What is the behavior of chromosome sets in the human life cycle?

  • At sexual maturity, ovaries and testes produce haploid gametes
  • Gametes are produced by meiosis
  • Meiosis results in one set of chromosomes in each gamete
  • Fertilization and meiosis alternate to maintain chromosome number

  
• What occurs during meiosis?

  It reduces the number of chromosome sets from diploid to haploid

  
• How many sets of cell divisions occur in meiosis?

  Two sets of cell divisions: meiosis I and meiosis II

  
• What is the result of meiosis?

  Four daughter cells with half as many chromosomes as the parent cell

  
• What happens in meiosis I?

  Homologous chromosomes separate

  
• What is synapsis in prophase I?

  Homologous chromosomes loosely pair up, aligned gene by gene

  
• What is the outcome of meiosis II?

  Four haploid daughter cells with unreplicated chromosomes

  
• What occurs during interphase before meiosis I?

  Chromosomes are replicated to form sister chromatids

  
• What is crossing over?

  Nonsister chromatids exchange DNA segments

  
• What forms a tetrad during meiosis?

  A group of four chromatids from homologous chromosomes

  
• What happens in metaphase I?

  Tetrads line up at the metaphase plate

  
• What occurs in anaphase I?

  Pairs of homologous chromosomes separate

  
• What happens during telophase I and cytokinesis?

  Each half of the cell has a haploid set of chromosomes
• What occurs between meiosis I and meiosis II?

  No chromosome replication occurs