1: Mitosis Flashcards Preview

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Flashcards in 1: Mitosis Deck (27):

In eukaryotes, where is nearly all of the DNA of a cell stored?

in the nucleus


How many metres of DNA does a human nucleus contain? How long is the human nucleus in diameter? How can all the DNA fit in the small nucleus?

- 2m
- 5um
- DNA molecule is so narrow - its width is is 2nm (0.002um)


Is a DNA molecule visible with a light microscope?



What do DNA molecules have attached to them in eukaryotes? What structure does this form?

have proteins attached to them, forming structures called chromosomes


What happens to the chromosomes during mitosis? What is this called? How does 'this' occur?

- chromosomes become shorter and fatter
- condensation
- through complex process called 'supercoiling'


When is it possible to see chromosomes through a light microscope?

when they are condensed during the early stages of mitosis


What sort of structure do chromosomes have when it is possible to see them with a light microscope?

a double structure


During the early stages of mitosis, what are the two parts of the chromosome called? What is the name of the point that holds the two parts of the chromosome together?

- sister chromatids
- the centromere


What does the term 'sister' indicate in 'sister chromatid'? How are they produced?

- that the two chromatids contain an identical DNA molecule
- produced by DNA replication before the start of mitosis


What happens to the centromere during mitosis? What is the result of this?

- centromere divides
- the sister chromatids separate


What are the sister chromatids referred to as after the centromere divides and they separate?

as chromosomes, rather than chromatids


State all the stages of mitosis.

1. early prophase
2. late prophase
3. metaphase
4. anaphase
5. early telophase
6. late telophase


What happens in mitosis: early prophase

- spindle microtubules are growing
- chromosomes are becoming shorter and fatter by supercoiling


What happens in mitosis: late prophase

- spindle microtubules extend from each pole to the equator
- each chromosome consists of two identical chromatids formed by DNA replication in interphase and held together by a centromere


What happens in mitosis: metaphase

- spindle microtubules from both poles are attached to each centromere, on opposite sides
- nuclear membrane has broken down and chromosomes have moved to equator


What happens in mitosis: anaphase

- spindle microtubules pull the genetically identical chromosomes to opposite poles
- centromeres have divided and the chromatids have become chromosomes


What happens in mitosis: early telophase

- spindle microtubules break down
- all chromosomes have reached the poles and nuclear membranes form around them


What happens in mitosis: late telophase

- chromosomes uncoil and are no longer individually visible
- cell divides (cytokinesis) to form two cells with genetically identical nuclei


Draw and label a cell undergoing mitosis (only include relevant parts of cell). (p14)



What is the mitotic index?

the ratio between the number of cells in mitosis in a tissue and the total number of observed cells


State the formula for mitotic index.

= number of cells in mitosis/ total number of cells


How is the mitotic index used?

by doctors to predict how rapidly a tumour will grow and therefore what treatment is needed


What does a high mitotic index indicate?

a fast-growing tumour


What is cytokinesis?

the division of the cytoplasm to form two cells


When does cytokinesis occur?

after mitosis and is different in plant and animal cells


How does cytokinesis occur in plant cells?

a new cell wall is formed across the equator of the cell, with plasma membrane on both sides. This divides the cell in two.


How does cytokinesis occur in animal cells?

the plasma membrane at the equator is pulled inwards until it meets in the centre of the cell, dividing it in two

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