Mitosis

Question 1

What is the role of mitosis?

Answer 1

Form of cell division that produces identical cells, there are four stages of mitosis: prophase, metaphase, anaphase and telophase.

Question 2

Outline what happens in Prophase

Answer 2

• Chromosomes condense, becoming visible: 2 sister chromatids joined at centromere)
• Centrioles move to opposite poles of cells & mitotic SF form.
• Nuclear envelope & nucleolus is break down = chromosomes free in cytoplasm

Question 3

Outline what happens during Metaphase

Answer 3

Sister chromatids line up at cell equators attached to the mitotic spindle by their centromeres

Question 4

Outline what happens during Anaphase

Answer 4

• Spindle rivers contract = Centromeres divide
• 👯‍♀️ chromatids separate into 2 rusticity chromosomes & pulled to opposite poles of cell (look V shaped both ends)
• SF break down

Question 5

Outline what happens during Telophase

Answer 5

• Chromosomes decondense, becoming invisible again.

- New nuclear envelopes form around each set of chromosomes = 2 New nuclei, each with 1 copy of each chromosome

Question 6

Outline what happens during Interphase

Answer 6

G1 = Cell synthesises proteins eg tubulin for SF & cell doubles

S PHASE = 🧬 replicates and chromosomes consist of 2 sister chromatids joined together by centromeres

G2 = organelles divide and cells keep growing and proteins needs for the next cell division

Question 7

Cytokinesis

Answer 7

during cytokinesis the parent and replicated organelles move to opposite sides of the cell and the cytoplasm divides thus producing two daughter cells.

Question 8

Importance of Mitosis

Answer 8

• Growth: all cells produced are identical so organisms can grow using mitosis.
• Repair: all cells produced are identical so organisms can replace dead tissues using mitosis.
• Reproduction: some single-celled organisms, like yeast, reproduce by dividing into two identical daughter cells by mitosis.

Question 9

What is the process in which prokaryotic cells divde.

Answer 9

Binary fission

Question 10

Steps of binary fission:

Answer 10

1. The circular DNA in the cells replicates and both copies attach to the cell membrane. Plasmids also replicate.
2. The cell membrane then begins to grow between the two DNA molecules and begins to pinch inwards, dividing the cytoplasm in two.
3. A new cell wall forms between the two DNA molecules dividing the original cell. The identical daughter cells each have a single copy of the circular DNA and a variable number of copies of the plasmids

Question 11

Why do viruses not undergo cell divison.

Answer 11

viruses are non-living - following the injection of their

nucleic acids into another cell, the infected host cell replicates the virus particles.

Question 12

Stages of mitosis - Mitosis

Answer 12

Metaphase

The chromosomes line up along the mid-line of the cell.

Question 13

Stages of mitosis - Anaphase

Answer 13

Anaphase

The chromosomes break into two chromatids - these sister chromatids separate at the centromere.

Question 14

Stages of mitosis - Telophase

Answer 14

Telophase

The chromatids reach the opposite poles and begin to decondense, becoming chromosomes again.

Question 15

Stages of mitosis - Prophase

Answer 15

Prophase

The nuclear envelope breaks down and the nucleolus disappears. Chromosomes are left floating in cytopla

Question 16

Simple steps for investigating mitosis

Answer 16

1. Prepare sample
2. Cut the root tipes from meristem
3. Stain the root tips
4. Squash the root tips
5. View sample at 400x power under light microscope.

Question 17

What is the Mitosis index

Answer 17

is used to work out the proportion of cells in the sample that are in mitosis.

Question 18

Equation for Mitotic index

Answer 18

Mitotic index = number of cells in mitosis ÷ total number of cells

Question 19

How can a cell size be measured?

Answer 19

using a micrometer and graticule.

Question 20

Somatic cell

Answer 20

A cell that contain two sets of chromosomes (one inherited from the father and the other inherited from the mother) known as diploid number 2N, while the gametes (male sperms and female ova) contain the haploid number N.

Question 21

Diploid

Answer 21

a cell that contain two copies of each chromosome.

Question 22

Haploid

Answer 22

a cell that contains a single set of chromosomes. eg gametes sperm and egg cell

Question 23

Compare and contrast a human somatic cell to a human gamete.

A-A* (AO3/4)

Answer 23

Somatic cells have 46 chromosomes and are diploid whereas gametes have half as many chromosomes as found in somatic

Question 24

How do microtubules connect to chromosomes?

Answer 24

Microtubules bind to a protein complex on each chromosome, known as a kinetochore.

The kinetochores are located at the centrosome of each chromosome. This is a region of the DNA which the kinetochore proteins bind to.