Cell and nuclear division

Learning objectives

(HL) Describe the cell cycle as interphase, consisting of G1, S and G2, followed by mitosis and cytokinesis, and state what happens to the DNA and the organelles during each stage

Describe the events of prophase, metaphase, anaphase and telophase in terms of the supercoiling of chromosomes, the formation of the spindle, the alignment of chromosomes at the equator and the separation of sister chromatids, and calculate a mitotic index from a micrograph

Compare cytokinesis in animal cells by constriction with cytokinesis in plant cells by the formation of a cell plate

Explain meiosis as two divisions that halve the chromosome number, describe the pairing of homologous chromosomes and crossing over in prophase I and the independent orientation of bivalents in metaphase I, and explain how both processes generate genetic variation in gametes

Explain non-disjunction as the failure of chromosomes or chromatids to separate, relate it to conditions such as Down syndrome, and interpret a karyogram to determine sex and to identify a chromosomal abnormality

(HL) Explain the control of the cell cycle by cyclins at checkpoints, and explain how mutations in proto-oncogenes and tumour suppressor genes lead to uncontrolled division, tumour formation and metastasis