Cell Division

Question 1

Chromosomes

What are chromosomes made up of?

Answer 1

Chromosomes consist of DNA molecules combined with proteins. They contain genes which provide the instructions for protein synthesis.

Question 2

Chromosomes

What is a gene?

Answer 2

A section of DNA which codes for a protein.

Question 3

Chromosomes

How many chromosomes are found in the nucleus of the human body?

Answer 3

46 in 23 pairs

Question 4

Chromosomes

How many chromosomes are found in the nucleus of gametes?

Answer 4

23

Question 5

Mitosis and the cell cycle

What are the three main stages of the cell cycle?

Answer 5

1. Replication of DNA and synthesis of organelles
2. Mitosis
3. Division of cells

Question 6

Mitosis and the cell cycle

Why is mitosis important?

Answer 6

• Produces identical cells which have all the same genetic information
• Produces additional cells for growth and repair

Question 7

Mitosis and the cell cycle

Describe the first stage of the cell cycle.

Answer 7

Longest stage- cells grow and increase in mass, replicate DNA and synthesise more organelles.

Question 8

Mitosis and the cell cycle

Descirbe the second stage of the cell cycle.

Answer 8

Each chromosome in a pair is pulled to opposite poles of the cell, then the nucleus divides.

Question 9

Mitosis and the cell cycle

Describe the third stage of the cell cycle.

Answer 9

The cytoplasm and cell membrane divide - two identical daughter cells are produced

Question 10

Stem cells

What is a stem cell?

Answer 10

An unspecialised cell which is capable of differentiating into other cell types and of self-renewable

Question 11

Stem cells

What is the function of stem cells in embryos?

Answer 11

• Embryonic stem cells can replicate themselves and differentiate into many other types of cells
• Embryonic stem cells may be able to treat conditions such as paralysis and diabetes by dividing to replace damaged stells

Question 12

Stem cells

What is the function of stem cells in adult bone marrow?

Answer 12

Adult stem cells can differentiate into several cell types to replace dead or damaged tissues. For example, bone marrow stem cells can form many different types of blood cell.

Question 13

Stem cells

What is the function of stem cells in plant meristems?

Answer 13

Meristem stem cells retain the ability to differentiate into any type of plant cell throughout their lifespan - they can differentiate into any cell which is required ny the cell.

Question 14

Stem cells

What is theraputic cloning?

Answer 14

A cloning method where an embryo is produced with the same genetic makeup as the patient. The stem cells which originate from the embryo will not be rejected by the patients immune system, so can be used to treat certain medical conditions.

Question 15

Stem cells

What are the dvantages of using meristem stem cells to clone plants?

Answer 15

• Can prevent rare plants from becoming extinct
• Can produce large numbers of plants with favourable characteristics
• Can produce identical plants for research

Question 16

Stem cells

What issues are associated with the use of embryonic stem cells?

Answer 16

• Many embryonic stem cells are sourced from aborted embryos - some people have an ethical or religious objection.
• Development of stemcell therapies is slow, expensive and difficult.
• Adult stem cells infected with viruses could transfer infections to patient.
• If donor stem cells do not have the same genetic makeup to the patient, an immune response could be triggered.