MEIOSIS A-Level Biology

• According to the introduction, what is the video about?

  Meiosis for A-level Biology
• What type of cell division is meiosis?

  A type of cell division
• How many nuclear divisions are involved in meiosis?

  Two
• How does meiosis differ from mitosis regarding genetic variation?

  Meiosis introduces genetic variation
• How many daughter cells are produced as a result of meiosis?

  Four
• What does "haploid" mean in the context of daughter cells produced by meiosis?

  One set of chromosomes
• What is the ploidy of the parent cell before meiosis?

  Diploid
• Where in the cell cycle do chromosomes double before meiosis?

  Interphase
• What are the two mechanisms that introduce variation in meiosis?

  Independent segregation and crossing over
• In which division of meiosis do independent segregation and crossing over occur?

  Meiosis 1
• What are homologous chromosomes?

  Chromosomes with the same genes
• What lines up at the equator during independent segregation?

  Homologous pairs
• What determines which side of the equator homologous chromosomes end up on?

  It is random
• What happens to the pairs after they line up at the equator?

  Pairs are separated to either side
• What mathematical formula is used to calculate the possible combinations of chromosomes in gametes due to independent segregation?

  $2^n$
• In the formula $2^n$, what does 'n' represent?


  Number of homologous pairs
• When does crossing over occur during meiosis?

  Meiosis 1
• For humans, with 23 pairs of chromosomes, how many possible combinations of chromosomes can be made in gametes due to independent segregation?

  Over 8 million
• During crossing over, what structures get tangled and twisted?

  Chromatids
• What event is caused by the tension on chromatids during crossing over?

  Part of the chromatid snaps
• What is the result of chromatids breaking and recombining during crossing over?

  New combinations of alleles
• Which part of the chromosome actually breaks and recombines during crossing over?

  The chromatid
• How many nuclear divisions occur in meiosis compared to mitosis?

  Two in meiosis, one in mitosis
• What type of cells are produced by meiosis in terms of chromosome number?

  Haploid cells
• What is produced by mitosis in terms of chromosome number?

  Diploid cells
• What is the genetic outcome of mitosis?

  Genetically identical cells
• What is the key characteristic to look for on a lifecycle diagram to identify where meiosis occurs?

  Diploid cell becoming a haploid cell
• How is a diploid cell represented?

  2n
• How is a haploid cell represented?


  n
• Can organisms create gametes by mitosis?

  Yes
• What process introduces even more variation after meiosis?

  Fertilization
• In humans, approximately how many possible combinations of chromosomes are there after fertilization?

  $7.04 x 10^{13}$
• How many possible combinations of chromosomes do we have after fertilization?

  $2^n$ squared
• What explains the lack of genetically identical humans (excluding identical twins)?

  Variation introduced by meiosis and fertilization
• Does crossing over increase variation by more than just independent assortment?

  Yes
• What are alleles?

  Different versions of a gene