Cell Division

Question 1

What is dna

Answer 1

DNA is a molecule which carries the instructions (genes) which controls the activity if the cell

Question 2

What is a chromatin

Answer 2

In eukaryotes DNA is tightly wrapped around proteins called histones. The DNA and histone proteins together are called chromatin which can be made visible by staining

Question 3

What is a single chromosome

Answer 3

 Is one long linear double stranded molecule of DNA. single chromosomes are relaxed and not visible under a light microscope

Question 4

What is a duplicated chromosome (relaxed)

Answer 4

Chromosomes are replicated before a cell divides each chromosome consists of two genetically identical copies called sister chromatids how together by a shared centromere

Question 5

What is a duplicated chromosome (supercoiled)

Answer 5

During mitosis chromosomes shorten and thicken so they are sturdy enough to move around the cell. individual chromosomes are only visible when they are super coiled

Question 6

In humans the normal diploid number of chromosomes is

Answer 6

46

Question 7

Chromosomes exist in pairs called

Answer 7

homologous pairs. human cells normally contain 23 pairs of chromosomes

Question 8

Homologous chromosomes are

Answer 8

The same size and same shape and carry the same genes

Question 9

Sex cells are

Answer 9

Haploid cells

Question 10

The cell cycle is divided into what is three main stages

Answer 10

Interphase, mitosis and cytokinesis

Question 11

Describe what happens during interphase

Answer 11

During stage G1 Proteins are synthesised and organelles are replicated (5hr)
During stage S DNA is replicated (7hr)
During stage G2 the cell grows (3hr)

Question 12

Describe what happens in mitosis

Answer 12

Mitosis has four stages prophase metaphase anaphase and telophase and it involves the division of a nucleus into two genetically identical nuclei

Question 13

Describe what happens during cytokinesis👍🏻

Answer 13

The cytoplasm divides to produce 2 genetically identical cells

Question 14

How can cells in interphase be recognised

Answer 14

1. they have no visible chromosomes because they’re relaxed
2. they have a visible nucleus because the nuclear envelope is still intact

Question 15

Mitosis increases cell number for

Answer 15

1. tissue growth
2. tissue repair
3. asexual reproduction in some organisms

Question 16

Describe what happens during prophase

Answer 16

Chromosomes shorten and thicken (supercoil) So become visible. Each consists of two chromatids joined by a centromere and the nuclear envelope disintegrates. centrioles move to opposite poles of the cell and they start to make spindle fibres

Question 17

Describe what happens during metaphase

Answer 17

Chromosomes attach to spindle fibres by the central mass and move towards the cell equator and they align on the equator

Question 18

Describe what happens during anaphase

Answer 18

The centromere split and the spindle fibres contract and shorten the chromatids are then pulled apart and move to opposite poles of the cell. The centromeres move first

Question 19

What happens during telophase

Answer 19

Chromosomes relax (uncoil)at this cell pose meaning they become indistinct and the nuclear envelopes form around each set of chromosomes to nuclei form and cell goes into cytokinesis

Question 20

What is meiosis? 

Answer 20

Meosis this a type of cell division which involves two divisions of the parent cells to produce for genetically different daughter cells.

Question 21

What happens during meiosis?

Answer 21

Homologous chromosome pairs, separate during the first division and sister chromatids separate during the second division these daughter cells are called gametes which are sex cells and therefore the parent cells diploid. The daughter sex cells will be haploid. This is important as it leads to sexual reproduction and genetic variation.

Question 22

Compare mitosis and meiosis

Answer 22

Mitosis has one division meiosis has two divisions
Mitosis produces two genetically identical daughter cells. Where as meiosis produces four genetically different cells
In mitosis, the number of chromosomes that the daughter cell has is the same as the parent cells in meiosis, it is not
Mitosis is used for growth and repair and asexual reproduction. Where is meiosis is used for sexual reproduction and genetic variation. 

Question 23

What is a tumour?

Answer 23

A Mass of abnormal and differentiated cells produced by uncontrolled cell division 

Question 24

What is a malignant tumour?

Answer 24

-malignant tumours cause cancer
-grow rapidly
-Invade and destroy surrounding tissues
-Cancer cells can break off from the tumour and migrate to other parts of the body and blood or lymph to set up secondary tumours elsewhere in the body. This process is called metastasis. 

Question 25

What is a benign tumour

Answer 25

-they do not cause cancer
-Grow slowly
-Do not invade and damage surrounding tissues?
-Do not undergo metastasis?
-Are usually harmless
-May damage organs are found in or cause blockages or pressure on surrounding organs

Question 26

The rate of the normal cell cycle is controlled by

Answer 26

Regulatory genes called Proto-oncogenes and tumour suppressor genes. These genes code for proteins to ensure that the cell cycle starts and stops when it should.

Question 27

Mutation of these regulatory genes is characterised by

Answer 27

An unusually large proportion of cells undergoing mitosis, leading to unusually rapid cell division

Question 28

What do proto-oncogenes code for?

Answer 28

Regulatory proteins that stimulate cell division. Mutated proto-oncogenes are called oncogenes. They overproduce the regulatory proteins, so that so division occurs too rapidly.

Question 29

What do tumour suppressor genes code for

Answer 29

Regulatory proteins that inhibit cell division. Mutated tumour, suppressor genes produce a non-functional regulatory protein that fails to inhibit so division division occurs to rapidly.

Question 30

What are the genetic factors that cause cancer?

Answer 30

Some cancers are caused by inheriting, mutated alleles of the genes that controls cells division. These are called hereditary gene mutations.

Question 31

What environmental factors cause cancer

Answer 31

Some cancers are caused by a car acquired Jean mutations of the genes that controls cell division. Exposure to radiation, mutagenic, chemicals, and high fat diet will increase the chances of a person developing certain cancers. Environmental changes can cause epigenetic changes during a persons lifetime such as Abnormal methylation of genes control inside a vision. These changes can also be inherited. 

Question 32

What prevents getting cancer from genetic factors?

Answer 32

-genetic screening to identify people who carried the mutated allele
-Regular screening for signs of cancer because the earlier the diagnosis is May, the greater the chance of effective treatment and recovery
-Preventative surgery for example, women with the BRCA1 mutation may choose to have their breast removed


Question 33

What helps prevent environmental factors from causing cancer?

Answer 33

UV radiation in sunlight is a mutagen, its genes that controls cell division in the skin. White people are more at risk of developing skin cancer as the skin has less melanin. Melanin protect the skin from the UV radiation in sunlight. Avoiding excessive exposure to the Sun or using sunscreen is the block UV radiation reduces the risk of developing skin cancer