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1.7 Mammalian Cell Division 👩‍👧‍👧

cell division

Introduction to mammalian cell division

Mammalian cell division is a core JC1 topic in H2 BIO A levels. This topic traces all the events leading up to cytokinesis. And it results in 2 daughter cells after each division in both mitosis and meiosis. One should focus on the differences between the 2 types of cell division as well as proper phrasing exactly describing the processes.

Materials for mammalian cell division

Phrasing errors

  • A pair of bivalents.
  • Diploid number = amount of DNA.
  • Crossing over results in new alleles/genes formed.
  • In meiosis II, the 2 sister chromatids are not identical to each other.
  • An organism is sterile because its gametes have non-homologous chromosomes.
  • Chromosomes are pulled to the opposite ends of the cells by spindle fibers.
  • DNA replication happens in the interphase between meiosis I and II.
  • Chromosomes replicate during interphase.
  • Centromeres split during anaphase.
  • Sister chromatids separate to become individual chromatids.
  • Random orientation/random alignment of homologous chromosomes at metaphase followed by random separation of homologous chromosomes at anaphase I leads to random assortment.
  • Crossing over results in the exchange of genes/part of gene/part of allele/gene loci/gene contents/genetic material/DNA content/genetic information between non-sister chromatids.

Exam tips

  • Microtubules ≠ spindle fibre/microtubules ≠ mitotic spindle.
  • A diploid cell already becomes haploid at the end of meiosis I.
  • Synapsis is the process of pairing up homologous chromosomes. It has to occur first before crossing over can occur. Synapsis is not crossing over.
  • When given a graph and asked to identify the various stages of cell nuclear division, take note of what the y axis is referring to: amount of DNA or number of chromosomes per cell or per nucleus.
  • Centromeres do not interact with the spindle microtubules directly but to kinetochore proteins that are attached to the centromere.