Cell division by Mitosis + Stem Cells

Question 1

What is found in the nucleus

Answer 1

Chromosomes are found in the nucleus

Question 2

What are chromosomes made up of

Answer 2

Chromosomes are made up of a molecule called DNA.

Question 3

What do body cells contain

Answer 3

Body cells contain two of each chromosome. They are paired

Question 4

How many pairs of chromosomes do Human body cells contain

Answer 4

Human body cells contain 23 pairs of chromosomes

Question 5

What types of cells in have chromosomes that are not paired

Answer 5

Gametes have chromosomes which are not paired (human gametes have 23 single chromosomes)

Question 6

How many chromosomes do human gametes have

Answer 6

human gametes have 23 single chromosomes

Question 7

What do chromosomes carry

Answer 7

Chromosomes carry a large number of genes which determine many of our features

Question 8

Rank from biggest to smallest
cell, chromosome, gene, dna, nucleus

Answer 8

Cell, nucleus, chromosomes, DNA, Gene

Question 9

What is a chromosome

Answer 9

A chromosome is a long molecule of DNA found in the nucleus.

Question 10

What is DNA

Answer 10

DNA is the molecule in cells that stores genetic information

Question 11

What is a gene

Answer 11

A gene is a short section of DNA, found on a chromosome, which contains the instructions needed to make a protein

Question 12

What is a gamete

Answer 12

A sex cell e.g. an egg cell or a sperm cell in animals

Question 13

Describe the process of mitosis

Answer 13

In the first stage of the cell cycle, the DNA replicates to form two copies of each chromosome

The cell also grows and copies its sub-cellular structures such as mitochondria and ribosomes

In the second stage of the cell cycle, mitosis takes place.
One set of chromosomes is pulled to each end of the cell. The nucleus also divides

In the final stage of the cell cycle, the cytoplasm and the cell membrane divide to form identical cells.

Question 14

Which stage of the cell cycle takes the longest

Answer 14

Replication of DNA to form copies of each chromosome and synthesis of new sub-cellular structures.

Question 15

Functions of mitosis/Importance of mitosis

Answer 15

1. Mitosis is essential for growth and development of multicellular organisms (e.g. plants and animals)
2. Mitosis takes place when an organism repairs itself (e.g. when a broken bone heals)
3. Mitosis happens during asexual reproduction

Question 16

What is a stem cell

Answer 16

A stem cell is an undifferentiated cell which can give rise to more cells of the same type and can differentiate to form other types of cells

Question 17

What is an embryonic stem cell

Answer 17

Embryonic stem cells are stem cells from an early embryo that can differentiate to form the specialised cells of the body

Question 18

What are adult stem cells

Answer 18

Adult stem cells are stem cells that are found in adults that can differentiate and form a limited number of cells

Question 19

Describe why differentiation is important in living organisms

Answer 19

All cells in an early animal or plant embryo are unspecialised (stem
cells).
Differentiation fulfils organisms’ requirements for different cells to carry
out different roles (e.g., muscle cells, sperm cells, gut lining cells).

Question 20

Describe where stem cells are found in animals and plants

Answer 20

In animals
Embryonic stem cells are found on the inside layer of an embryo
Adult stem cells are found in bone marrow, skin, eyes, brain

Question 21

Describe the process of differentiation

Answer 21

A sperm cells joins with an ovum (egg cell) to form a zygote, a single new cell. This is called fertilisation.

The fertilised ovum now undergoes mitosis and forms a ball of cells called an embryo. The inner cells of this ball are the embryonic stem cells that differentiate to form all of the specialised cells of your body.

Overtime these cells continue to undergo mitosis. They also change and begin to form specialised cells such as nerve cells and muscle cells.

This process is called differentiation

Question 22

Order the steps of differentiation

Ovum + sperm cell
Embryo
Fertilised ovum
Nerve cells + muscle cells

Answer 22

Ovum + sperm cell
Fertilised ovum
Embryo
↓ differentiation
nerve cells + muscle cells

Question 23

Adult stem cells are only found in _____

Answer 23

Adult stem cells are only found in certain places

Question 24

Describe the function of stem cells in embryo’s

Answer 24

Stem cells from human embryos can be cloned and made to differentiate into most different types of human cells.

Question 25

Describe the function of stem cells in adult animals

Answer 25

Stem cells from adult bone marrow differentiate to form cells found in our blood such as: red blood cells, white blood cell and platelets

Question 26

Adult stem cells ______ differentiate into any other ______of cell

Answer 26

Adult stem cells cannot differentiate into any other type of cell

Question 27

State some ways that stem cells are useful in medicine

Answer 27

Bone marrow transplants
Therapeutic cloning

Question 28

Explain how stem cells are used in bone marrow transplants

Answer 28

Leukaemia is a cancer of the bone marrow.
To treat this, the patient’s existing bone marrow is destroyed using radiation
The patient then receives a transplant of bone marrow from a donor
The stem cells in the bone marrow divide and form new bone marrow. They also differentiate and form blood cells.

Question 29

Problems with bone marrow transplants

Answer 29

The donor has to be compatible with the patient. Otherwise the white blood cells produced by the donated bone marrow could attack the patient’s body.

There is a risk that viruses can be passed from the donor to the patient.

Question 30

Explain how stem cells are used in therapeutic cloning

Answer 30

In therapeutic cloning, an embryo is produced with the same genes as the patient

This means that stem cells from the embryo can be transplanted into the patient without being rejected by the patient’s immune system.

Once inside the patient, the stem cells can then differentiate to replace cells which have stopped working correctly

This technique could be useful for a range of medical conditions such as diabetes or paralysis

Question 31

Evaluate the use of embryonic stem cells and adult stem cells

Answer 31

The advantages of using embryonic stem cells is that many embryos can be created. It is a painless technique. Embryonic stem cells can also become any type of cell therefore treating many diseases

The disadvantages of using embryonic stem cells is that there is a possibility of harm or death to the embryo. The embryo cannot consent to the use of it’s cells. Also using embryonic stem cells is a unreliable technique that may not work

The advantages of using adult stem cells is that there are no ethical issues as patients can give permission. The adults stem cells can treat some diseases, the procedure is relatively sae and does not kill the donor. Patients recover quickly from the procedure and it is a reliable procedure.

The disadvantages of using adult stem cells is risk of infection from the procedure, it can only treat a few diseases and the procedure can be painful.

Both procedures advantage
Can treat the disease/problem

Both procedures disadvantages
risk of transfer of viral infection
Some stem cells can grow out of control and may become cancerous

In conclusion, even though the procedure when using adult stem cells is both ethical and reliable, the embryonic stem cell procedure is much more useful as it can treat many diseases.

Question 32

What do roots and buds contain

Answer 32

Roots and buds contain meristem tissue

Question 33

Describe the function of meristem cells in plants

Answer 33

Meristem tissue in plants can differentiate into any type of plant cell,
at any point in the life of the plant

Question 34

State the advantages of using meristem cells

Answer 34

A rare plant could be cloned to stop it from going extinct.
Cloned crop plants could be produced for farmer

• Crop plants with special features such as disease resistance can be
  cloned to produce large numbers of identical plants for farmers.