Sex and recombination

• What is sex in biological terms?

  Biological reproduction involving genetic exchange
• What is recombination?

  Genetic process of exchanging DNA segments
• Why do we have sex and recombination?

  To increase genetic diversity and adaptability
• What are the differences between meiosis and mitosis?

  Meiosis produces gametes; mitosis produces somatic cells
• What are the phases of meiosis?

  Prophase, Metaphase, Anaphase, Telophase
• In which phase of meiosis does homologous recombination occur?

  Prophase I
• What can cause double strand breaks in DNA?

  Radiation and chemical mutagens
• What is used as a template for repair in homologous repair of double strand breaks?

  Homologous chromosome
• What happens during strand invasion in homologous recombination?

  Free 3' end invades unbroken DNA molecule
• What occurs after the loop is displaced from the unbroken molecule?

  It pairs with the non-invading strand
• What are the two structures formed during homologous recombination?

  Two Holliday junctions
• Does homologous repair of a double strand break always result in crossing over?

  No, other outcomes are possible
• How does recombination affect genetic diversity?

  It shuffles alleles at different genetic loci
• What is one benefit of recombination in evolution?

  Allows adaptive response to environmental change
• How does recombination prevent genetic hitchhiking?

  Decouples beneficial alleles from harmful ones
• What is the effect of recombination on deleterious genes?

  Prevents accumulation of deleterious genes
• What is the role of the sex determining allele in recombination?

  It suppresses recombination between sex chromosomes
• Why does the Y chromosome not recombine with the X chromosome?

  Y does not recombine except for a small region
• What is the consequence of Y chromosome degeneration?

  Y has far fewer functional genes than X
• What has happened to the Y chromosome in mole voles and spiny rats?

  It has already been lost
• What has taken over sex determination in some species?

  Another sex determination gene on a different chromosome