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 onthe differences between the 2 types of cell division as well as proper phrasing exactly describing the processes.

    Useful study resources for mammlian cell division

    Most common phrasing errors made by students during exams

    • 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

    • Cell cycle ≠ cell division
    • 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

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