Heredity

• What are the benefits and disadvantages of asexual reproduction?

  Benefits:

  • Rapid process
  • Requires less energy
  • Only one parent needed

  
  

  Disadvantages:

  • Produces identical organisms
  • Limited ability to adapt/evolve
  • Not effective in changing environments

  
• What are the benefits and disadvantages of sexual reproduction?

  Benefits:

  • Creates genetic diversity
  • Allows adaptation to changing environments

  
  

  Disadvantages:

  • Requires two parents
  • Takes longer than asexual reproduction
  • Requires more energy

  
• What are the three types of life cycles based on DNA content?

  1. Haploid Majority
  2. Diploid Majority
  3. Alternation of Generations

  
• What occurs during meiosis?

  • Reduces chromosome number by half
  • Creates four genetically distinct haploid cells
  • Increases genetic diversity

  
• What are the stages of Meiosis I?

  1. Prophase I
  2. Metaphase I
  3. Anaphase I
  4. Telophase I

  
• What happens during Prophase I of meiosis?

  Chromatin condenses to form bivalent chromosomes

  
• What occurs during Metaphase I of meiosis?

  Homologous pairs align on the metaphase plate

  
• What is independent assortment in meiosis?

  Random alignment of homologous pairs during Metaphase I
• What is the significance of independent assortment?

  It increases genetic variation in gametes
• What happens during Anaphase I of meiosis?

  Homologous chromosomes are pulled to opposite poles

  
• What occurs during Telophase I of meiosis?

  Nuclear envelopes form around each set of chromosomes

  
• What is interkinesis?

  A short period between Meiosis I and II
• What is the overall outcome of Meiosis I?

  • Begins with 1 diploid germ cell
  • Ends with 2 haploid cells
  • Both cells possess bivalent chromosomes

  
• What happens to chromosome pairs at the end of telophase I?

  They reach the poles of the cell.
• What forms around each set of chromosomes after telophase I?

  Nuclear envelopes form around each set.

  
• What is the result of cytokinesis following telophase I?

  It produces two haploid cells.

  
• How do the chromosome numbers of the new cells compare to the original germ cell?

  They have half the number of chromosomes.
• How do we count chromosomes in a cell?

  By counting the number of centromeres present.
• What is the significance of bivalent chromosomes at the end of telophase I?

  Each bivalent has one centromere.
• What is Meiosis I often referred to as?

  Reductive division.
• What is the starting and ending cell type of Meiosis I?

  Starts with diploid germ cell, ends with haploid cells.

  
• What occurs during interkinesis?

  • Short interphase-like period between Meiosis I and II
  • No DNA replication occurs
  • Spindle disassembles and reassembles into two new spindles

  
• What happens to the nuclear envelopes during prophase II?

  They disintegrate in each cell.
• How does prophase II compare to prophase in mitosis?

  Prophase II is almost identical to mitosis prophase.
• What occurs during metaphase II?

  Chromosomes align on the metaphase plate.

  
• What happens during anaphase II?

  Centromeres separate and sister chromatids move apart.
• What is produced during telophase II?

  Four genetically different daughter cells.

  
• What is the role of meiosis in gametogenesis?

  • First step in gamete creation
  • Occurs only in gonads
  • Produces four haploid gametes from one diploid germ cell

  
• What is nondisjunction?

  Failure of chromosomes to separate properly.
• What are the three forms of nondisjunction?

  Meiosis I, meiosis II, and mitosis.
• What condition results from nondisjunction?

  Aneuploidy, or abnormal chromosome numbers.
• What is the most common result of fertilization after nondisjunction?

  Miscarriage.
• What is a karyotype?

  A picture of a person's chromosomes.

  
• How are chromosomes arranged in a karyotype?

  By size into homologous pairs.
• What are chromosomal rearrangements?

  Changes affecting large chunks of chromosomes.
• What are the four main types of chromosomal rearrangements?

  1. Duplication
  2. Deletion
  3. Inversion
  4. Translocation
• What is Cri Du Chat syndrome caused by?

  Deletion of part of chromosome 5.
• What is Fragile X syndrome caused by?

  Duplication of part of the X chromosome.
• What does the Philadelphia chromosome cause?

  A severe form of leukemia.
• How does crossover frequency relate to linked genes?

  • Measures how often two genes end up on opposite chromosomes
  • Helps estimate gene order and distances on chromosomes
  • Expressed in centimorgans or map units