B2 Cell Division

Question 1

Describe the first stage of the cell cycle

Answer 1

The cell grows in size, and increases the number of sub cellular structures e.g. mitochondria and ribosomes. Next, the DNA replicates to form 2 copies of each chromosome

Question 2

What are the three stages of mitosis?

Answer 2

Growth
DNA Replication + Mitosis
Cytokinesis (Division)

Question 3

Describe the second stage of the cell cycle

Answer 3

Mitosis occurs, one set of chromosomes is pulled to each end of the cell and the nucleus also divides

Question 4

Describe the final stage of the cell cycle

Answer 4

The cytoplasm and cell membrane divide to form two identical daughter cells

Question 5

What is the function of mitosis?

Answer 5

• Growth and development of multicellular organisms
• For repair
• During asexual reproduction

Question 6

What are embryonic stem cells?

Answer 6

Undifferentiated cells in a human embryo

Question 7

What do adult bone marrow stem cells differentiate into?

Answer 7

Blood cells

Question 8

What are three disadvantages of adult bone marrow stem cells?

Answer 8

• They must be compatible with the patient’s body, or
  they could be rejected
• They can only differentiate into blood cells (limited
  range)
• There is a risk that viruses can be spread from a
  donor to a patient

Question 9

What are the advantages of adult bone marrow stem cells?

Answer 9

There are no ethical objections towards it

No damage to embryos

Adults can give/withdraw consent and regrow cells neanmoins

Question 10

What are advantages of using embryonic stem cells?

Answer 10

• They can differentiate into many types of cells
• They can be used to create clones of plants (to
  prevent extinction)

Question 11

What are advantages of using embryonic stem cells?

Answer 11

• They can differentiate into many types of cells
• They can be used to create clones of plants (to
  prevent a crop’s extinction for farmers)

Question 12

What are the disadvantages of using embryonic stem cells?

Answer 12

Many stem cells come from aborted embryos, and many people believe that the embryo cannot consent to being used and is a violation of human rights (ethical)

Question 13

What is therapeutic cloning and what are its benefits?

Answer 13

Where an embryo is produced with the same genes as the patient, so that stem cells from that embryo can be transplanted into the embryo without the patient’s immune system rejecting them. Once inside the patient, the stem cells can differentiate to replace cells which have stopped working correctly

Question 14

What medical conditions could therapeutic cloning be used for?

Answer 14

Diabetes and Paralysis

Question 15

Where is meristem tissue found?

Answer 15

In the roots and buds of a plant

Question 16

What is meristem tissue?

Answer 16

Plant tissue which can differentiate into any type of plant tissue, at any point in the plant’s life

Question 17

Explain how the difference in differentiation patterns affects the ability to clone animals and plants

Answer 17

Most animal stem cells differentiate permanently in early stages of the embryo’s development, and cannot change back. On the other hand, most plant cells are able to differentiate all throughout their lives, and often don’t differentiate until they reach the final position in the plant

Question 18

What diseases can stem cells be used to treat?

Answer 18

Diabetes and Paralysis

Question 19

How can meristem tissue be used?

Answer 19

• To produce identical plants with desirable traits e.g. disease
  resistance
• To clone to prevent extinction or ^^^

Question 20

Explain why each chromosome must have 2 strands before a cell divides? [2]

Answer 20

• One copy of each chromosome goes to each offspring cell, so each offspring receives the same set of genetic material