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CAIE A-Level Biology 5.2.1 Chromosome Behaviour During Mitosis

Practise following replicated chromosomes from condensation and metaphase alignment through centromere division to equal sister-chromatid separation at opposite poles.

Syllabus
2028–2030
Course
Biology 9700
Level
AS

Exam points

  • connect pre-mitotic DNA replication with two genetically identical sister chromatids
  • describe chromosome alignment at the equator before centromeres divide longitudinally
  • explain spindle-driven chromatid movement to opposite poles as equal genetic separation

5.2.1—Chromosome behaviour in mitosis question 1

[Maximum number: 5]

During interphase of the cell cycle, individual chromosomes cannot be seen within the nucleus. The genetic material is termed chromatin during this stage.

Question (a)

(a)

Changes occur to chromatin during mitosis so that chromosomes become visible.

State what happens to chromatin so that individual chromosomes can be seen during mitosis.

[ 1 ]

Question (b)

(b)

Fig. 5.1 is a transmission electron micrograph of two human chromosomes at metaphase of mitosis.

magnification \(=\times 14000\)

magnification \(=\times 14000\)

Describe the structure of chromosomes at metaphase, such as the two chromosomes shown in Fig. 5.1.

[ 4 ]
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