Mitosis

Question 1

What does mitosis produce?

Answer 1

Two daughter cells that have the same number of chromosomes as the parent cell and each other (except in the case of mutation)

Question 2

What is interphase?

Answer 2

The period of time after mitosis in which no division occurs.

Question 3

What happens during interphase?

Answer 3

The replication of DNA.

Question 4

What happens in prophase?

Answer 4

1. This is when chromosomes first become visible.
2. Centrioles move to poles.
3. From each centriole spindles develop which then span from pole to pole.
4. The nucleolus disappears and the nuclear envelope breaks down, leaving chromosomes free in the cell.
5. Chromosomes are drawn towards the equator by the spindle fibres.

Question 5

What are centrioles?

Answer 5

Organelles contained by animal cells.

Question 6

What is the spindle apparatus?

Answer 6

The collective term for spindles formed from centrioles in prophase.

Question 7

How do we know centrioles aren’t necessary to spindle formation?

Answer 7

Plant cells do not have them and yet still form spindle fibres.

Question 8

What happens in metaphase?

Answer 8

The chromosomes are seen to be made up of two chromatids.
Chromatids are attached by a centromere, from the centromere, microtubules from the poles are attached.
The chromosomes are pulled by the spindle apparatus and arrange themselves across the equator of the cell..

Question 9

What is a chromatid?

Answer 9

Each chromatid is an identical copy of DNA from the parent cell.

Question 10

What happens during anaphase?

Answer 10

The centromeres divide into two and the spindle fibres pull the individual chromatids making them pull apart.
The chromatids move to their respective opposite poles of the cell and they are now called chromosomes.

Question 11

Where does the energy for the process come from?

Answer 11

It is provided by the mitochondria, which gather around the spindle fibres.

Question 12

What would happen if cells were treated with a chemical that destroyed the spindle?

Answer 12

The chromosomes would remain at the equator, unable to reach the poles.

Question 13

What happens during telophase?

Answer 13

The chromosomes reach their respective poles and become longer and thinner, finally disappearing leaving only widely spread chromatin.
The spindle fibres disintegrate and the nuclear envelope and nucleolus re-form.

Question 14

What happens during cytokinesis?

Answer 14

The cytoplasm divides, forming two cells.

Question 15

What is the name of the cell division that occurs in prokaryotic cells?

Answer 15

Binary fission.

Question 16

Explain the process of binary fission.

Answer 16

The circular DNA molecules replicates and both attach to the cell membrane.
Plasmids replicate.
The cell membrane grows between the two DNA molecules and pinches forward dividing the cytoplasm into two.
A new cell wall forms between the two molecules of DNA, dividing the cell into two daughter cells.

Question 17

After binary fission what do the two daughter cells contain?

Answer 17

A single copy of the circular DNA and a variable number of copies of the plasmids.

Question 18

How do viruses replicate?

Answer 18

By attaching to a host cell.
They inject their nucleic acid into the cell (the info on the acid provides instructions for host cell’s metabolic processes to start producing the viral components)
The host cell makes the vital components (nucleic acid, enzymes and structural proteins) which are assembled into new viruses.

Question 19

Why can viruses not undergo cell division?

Answer 19

They are non-living.

Question 20

Why does mitosis need to happen?

Answer 20

growth - when two haploid cells (sperm and ovum) fuse to form a diploid cell it has all the genetic info required, it just needs to grow.
Repair - if cells are damaged or if they die they need to be replaced.
Reproduction - single-celled organisms reproduce this way to produce two identical daughter cells.