Variation: Sexual Reproduction

• What is the main cause of genetic variation in organisms of the same species?

  Differences in DNA base sequences
• What is genetic variation?

  Small differences in DNA base sequences
• How is genetic variation transferred between generations?

  Through sexual reproduction
• What processes cause genetic variation during sexual reproduction?

  Crossing over, independent assortment, random fusion
• What happens during crossing over in meiosis?

  Non-sister chromatids exchange alleles

  
• What are chiasmata?

  Crossing points where chromatids entangle
• What stress occurs on DNA during crossing over?

  Entanglement of non-sister chromatids
• Why is crossing over significant?

  It results in new combinations of alleles

  
• Where is crossing over more likely to occur on a chromosome?

  Further from the centromere
• What is independent assortment?

  Random alignment of homologous pairs

  
• How does independent assortment increase genetic variation?

  By producing different combinations of alleles
• What formula calculates the number of different chromosome combinations?

  $2^n$
• What does random fusion of gametes create?

  Genetic variation between zygotes

  
• Why is it unlikely for offspring from sexual reproduction to be genetically identical?

  Due to random fusion of gametes
• How do mutations contribute to genetic variation?

  By generating new alleles
• What can happen to new alleles generated by mutations?

  They may remain hidden for generations
• What are the main sources of genetic variation?

  • Crossing over during meiosis
  • Independent assortment of chromosomes
  • Random fusion of gametes
  • Mutations
• How do the processes of crossing over and independent assortment contribute to genetic variation?

  • Crossing over: exchanges alleles between chromatids
  • Independent assortment: randomizes chromosome alignment
  • Both increase diversity in gametes and offspring

  
• Why can relatives differ genetically even with the same parents?

  • Genetic variation processes (crossing over, independent assortment)
  • Random fusion of gametes during fertilization