B2 Cell Division

Question 1

Chromosomes

Answer 1

Made of DNA molecules

Carries genes

The 46 chromosomes found in the human body are typically found as 23 pairs in the nucleus of body cells

Question 2

Genes

Answer 2

A section of DNA on a chromosome that codes for a particular sequence of amino acids, to make a specific protein

Question 3

The cell cycle

Answer 3

The series of events involved in cell growth and cell division

Allows for the growth, repair and asexual reproduction of cells

It involves:
Interphase
Mitosis
Cytokinesis

Question 4

Interphase

Answer 4

Extra ribosomes, mitochondria and other subcellular structures are produced

The cell’s chromosomes are replicated so that there are two sets of the cell’s chromosome.

Question 5

Mitosis

Answer 5

The duplication and distribution of chromosomes

Includes:
Prophase
Metaphase
Anaphase
Telophase

Question 6

Prophase

Answer 6

Chromosomes thicken and coil into chromatids, duplicate chromosomes

Disappearance of the nucleolus

Disintegration of the nuclear membrane

Organisation of fibres to form a spindle

Question 7

Metaphase

Answer 7

Chromosomes line up along the midline of the cell

Question 8

Anaphase

Answer 8

Chromatid pairs separate

Chromatids are pulled to opposite sides of the cell by spindle fibres

Question 9

Formula for length of cell cycle phase

Answer 9

(observed number of cells at that stage / total number of cells observed) * total length of time of a cell cycle

Question 10

Karyotype

Answer 10

A photo of an individual’s collection of chromosomes

Question 11

Asexual reproduction

Answer 11

Cellular reproduction that does not include the fusion of gametes or change in the number of chromosomes

Produces two identical cells

Question 12

Cytokinesis

Answer 12

The division of the cytoplasm and cell membrane of a parent cell to two daughter cells

Question 13

Growth

Answer 13

A permanent increase in size as a result of cell division or cell enlargement

Question 14

Stem cells

Answer 14

Cells with the ability to develop into a range of specialised cells

Question 15

Animal stem cells

Answer 15

Specialise in very early life

Mostly specialised by birth

Question 16

Specialised cells

Answer 16

Cells with features to specifically make them suited to complete a certain function

Cannot duplicate by mitosis and have to be replaced by stem cells

Question 17

Plant stem cells

Answer 17

Can differentiate throughout their lives

Undifferentiated cells are made at active regions of roots and stems called meristems

In meristems, mitosis takes place almost continuously

The plant cells do not differentiate until they have reached their final destination in the plant

Differentiation is not permanent- cells can redifferentiate

Question 18

Plant cloning

Answer 18

Identical plants can be made from a sample of leaf tissue quickly and economically

Under the right conditions, plant cells undifferentiate and undergo mitosis

These cells can differentiate to form the tissues needed to create a new plant

Question 19

Embryonic stem cells

Answer 19

Egg and sperm cells fuse to form a zygote

This grows into a ball of cells called an embryo

The inner cells of this ball are embryonic stem cells

They can differentiate into all of the specialised cells in the body

Question 20

Adult stem cells

Answer 20

Stem cells in the body when it is fully grown

An undifferentiated cell of an organism that can give rise to many more cells of the same type

Other types of cells can also arise from stem cells through differentiation

Question 21

Using stem cells

Answer 21

Embryonic stem cells can be encouraged to grow into almost any different type of cell needed in the body

Question 22

What conditions can be helped with stem cells

Answer 22

Paralysis

Diabetes

Vision impairment

Heart conditions

Question 23

Plant cloning for research

Answer 23

Plant cloning can produce large numbers of identical plants

This is important for research as scientists can change variables and observe the effect on genetically identical individuals

Question 24

Plant cloning for agriculture

Answer 24

Plant cloning can produce large numbers of identical plants with special features eg disease resistance

Question 25

Therapeutic cloning

Answer 25

The nucleus of a cell is inserted into a donor egg cell forming a blastocyst Stem cells from the blastocyst can be removed and cultures These cells are identical to the patient's, reducing the risk of transplanting as the immune stem accepts them

Question 26

Animal cloning through embryo transplant

Answer 26

An animal is artificially inseminated with sperm from a high yield male The embryo is then removed from the uterus Embryos can be split before they become specialised, this causes several identical embryos These can be transplanted to host mothers

Question 27

Animal cloning through adult cell cloning

Answer 27

The nucleus is removed from an unfertilised egg cell The nucleus from an adult body cell is inserted into the egg cell An electric shock stimulates the egg cell to divide to form an embryo These embryo cells contain the same genetic information as the adult cell When the embryo has developed into a ball of cells, it is inserted into the womb of an adult female to continue its development

Question 28

Medical problems with stem cell use

Answer 28

Can cause cancer if their growth is not controlled (especially in people with immunodeficiencies) Can transfer viruses Is considered a waste of money

Question 29

Ethical problems with stem cell use

Answer 29

The embryos can not consent its use (human rights violation) Human reproduction should not be interfered with (religious views)