Chromosome Behaviour in Mitosis (Cambridge (CIE) AS Biology): Flashcards
Exam code: 9700
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State the four main stages of mitosis, in order.
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State the four main stages of mitosis, in order.
Prophase
Metaphase
Anaphase
Telophase
What happens during prophase?
Chromosomes condense and become visible, each as two sister chromatids
The nuclear envelope breaks down
The spindle starts to form
What happens during metaphase?
Chromosomes line up along the equator (middle) of the cell
Spindle fibres attach to the centromeres
What happens during anaphase?
The centromeres divide
The sister chromatids are pulled apart to opposite poles of the cell by the spindle fibres
What happens during telophase?
The chromatids reach the poles and decondense
A new nuclear envelope forms around each group of chromosomes
Two new nuclei are formed
Chromosomes line up along the equator of the cell during .
Chromosomes line up along the equator of the cell during metaphase.
Sister chromatids are pulled to opposite poles of the cell during .
Sister chromatids are pulled to opposite poles of the cell during anaphase.
How does the behaviour of the cell surface membrane during division differ between animal and plant cells?
In animal cells, the cell surface membrane pinches inwards to divide the cell.
In plant cells, a new cell wall (cell plate) forms across the middle instead.
Why are root tips used to observe mitosis?
The tip of a root contains a region of actively dividing cells, so many cells are caught in the process of mitosis.
How can you identify which stage of mitosis a cell is in?
By the position and appearance of the chromosomes, e.g. chromosomes lined up along the equator indicate metaphase.
In a photomicrograph, how would you identify a cell in anaphase?
The chromatids are separating and being pulled towards opposite poles of the cell.
Outline how to prepare a root tip squash to observe mitosis.
Cut the tip from a growing root
Stain it so the chromosomes become visible
Squash the tip on a slide to spread the cells into a single layer
View under a microscope
The actively dividing cells used to observe mitosis are found in the of a root.
The actively dividing cells used to observe mitosis are found in the tip of a root.
True or False?
Most cells in a root tip sample are in mitosis at any one time.
False.
Most cells are in interphase; only a small proportion are actively undergoing mitosis at any one time.
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