Cell division

Question 1

What does a nucleus contain?

Answer 1

Chromosomes

Question 2

How many pairs of chromosomes are in a human nucleus?

Answer 2

23

Question 3

What does a chromosome contain?

Answer 3

Many genes

Question 4

What is a gene?

Answer 4

the code to make different proteins and control the development of different characteristics

Question 5

What are chromosomes made up of?

Answer 5

DNA

Question 6

What is mitosis?

Answer 6

single cell divides into two identical daughter cells

Question 7

Examples of some cells that divide by mitosis

Answer 7

• hair and nail cells
• skin cells
• red and white blood cells

Question 8

what are the steps of Mitosis

Answer 8

1) DNA replicates to form two copies of each chromosome
2) the membrane around the nucleus breaks down, the chromosomes condense and move freely in the cytoplasm
3) the chromosomes line up in the middle of the cell (equator)
4) the cell pulls apart the chromosomes into 2 arms. these are pulled to separated ends of the cell
5) the membrane forms around the sets of chromosomes on either ends of the cell. This forms 2 nuclei
6) the cytoplasm and cell membrane divide. The cell has non-identical 2 new daughter cells

Question 9

what are the steps of the cell cycle?

Answer 9

1) each cell grows and makes new subcellular structures
2) DNA is copied and new chromosomes are made
3) mitosis

Question 10

What are stem cells?

Answer 10

Unspecialised cells that can change to different types of cells

Question 11

Where are stem cells found? - animals

Answer 11

Human embryos and adult bone marrow

the umbilical cord of a newborn baby

Question 12

What can stem cells be used to treat?

Answer 12

Paralysis and diabetes

• treating conditions where cells are damaged or not working properly
• used to replace damaged cells

Question 13

Where are stem cells found? - plants

Answer 13

Meristems of plants

Question 14

Advantages of stem cells?

Answer 14

• They can be taken without hurting
• Will provide vital clues about how tissues develop
• Could treat Parkinson’s, Alzheimer’s, heart disease, strokes, arthritis, burns etc
• replace faulty cells

Question 15

Disadvantages of stem cells?

Answer 15

• Use of embryos is unethical
• Embryonic stem cell research = murder
• Immune system might recognise stem cells as foreign and be rejected and die
• transfer of viral infections

Question 16

What are embryonic stem cells?

Answer 16

stem cells from human embryos that can make all types of cells

Question 17

what is therapeutic cloning?

Answer 17

A cloned embryo of the patient may be made and used as a source of stem cells

Question 18

Why is therapeutic cloning beneficial?

Answer 18

the stem cells from the cloned embryo will not be rejected by the patient’s body, so they could be very useful in treating the patient.

Question 19

How do scientists use stem cells to create healthy organs that replace faulty ones?

Answer 19

• take the stem cells from the patient ( e.g. bone marrow)
• remove or fix a faulty gene
• insert the modified nucleus into a donor egg cell that has had the nucleus removed.This egg cell now thinks it’s been fertilised so it develops into an embryo
• Each cell in the embryo contains the DNA from the patient but without the faulty gene = embryonic stem cells
• remove the stem cells from the embryo and make them differentiate into the organ

Question 20

Advantages of stem cells for plants

Answer 20

• rare species can be cloned to protect them from extinction

- large numbers of identical crop plants with special features such as disease resistance, can be made