B2

Question 1

Where can genes be found?

Answer 1

Most cells have a nucleus. This contains genetic material in the form of chromosomes. Chromosomes are coiled up lengths of DNA molecules. Each chromosome carries a large number of genes (these control different characteristics). Body cells normally have two copies of each chromosome. Body cells have two copies of each chromosome (one from the father, one from the mother).

Question 2

Describe the cell cycle.

Answer 2

Body cells in mulitcellular organisms divide to produce new cells as part of a series called the cell cycle. The stage of the the cell cycle when the cell divides is called mitosis. 2) The stage of the cell cycle when the cell divides is called mitosis. Multicellular organisms use mitosis to grow or replace cells that have been damaged. The end of the cell cycle results in two new cells identical to the original cell, with the same number of chromosomes.

Question 3

How is DNA organised in cells that arent dividing?

Answer 3

It is all spread out in long strings.

Question 4

Desrcibe the stages of the cell cycle. 1

Answer 4

Before it divides it has to grow and increase the amount of subcellular structures such as mitochondria and ribosomes.

Question 5

Describe the stages of the cell cycle. 2

Answer 5

It then duplicates its DNA so theres one copy for each cell. The DNA is copied and forms X-shaped chromosomes. Each arm of the chromosome is an exact duplicate of the other.

Question 6

Describe the cell cycle. 3

Answer 6

The chromosomes line up at the centre of the cell and cell fibres pull them apart. The two arms of each chromosome go to opposite ends of the cell.

Question 7

Describe the cell cycle. 4

Answer 7

Membranes form around each of the sets of chromosomes. These become nuclei of the two new cells. The nucleus has divided.

Question 8

Describe the cell cycle. 5

Answer 8

Lastly the cytoplasm and the cell membrane divide.

Question 9

Why is the cell cycle important?

Answer 9

For growth, development and repair.

Question 10

What is differentiation?

Answer 10

The process by which a cell changes to become specialised for its job.

Question 11

What happens as cells change?

Answer 11

They develop different sub-cellular structures and turn into different types of cells. This allows them to carry out specific functions.

Question 12

When does most differentiation occur?

Answer 12

As an organism develops.

Question 13

What is differentitation in mature animals mainly used for?

Answer 13

Repairing and replacing cells

Question 14

What is the difference between animal cells and plant cells?

Answer 14

Most animal cells differentiate permanently in the embryo however lots of plants can undifferentiate.

Question 15

What is the cell cycle?

Answer 15

The process of division in a body cell that involves mitosis and results in the formation of two identical daughter cells.

Question 16

What is a stem cell?

Answer 16

An undifferentiated cell

Question 17

What can stem cells be used for?

Answer 17

Can divide to produce lots more undifferentiated cells. They can then differentiate into different types of cell, depending on what instruction they’re given.

Question 18

Where are stem cells found?

Answer 18

In early human embryos

Question 19

Where are stem cells found in adults?

Answer 19

Certain places like bone marrow. But they can’t turn into any cell type, only certain ones like blood cells.

Question 20

What can stem cells be used for?

Answer 20

In a lab, stem cells from embryos and bone marrow can be grown to produce clones
Made to differentiate into specialised cells used in medicine or research

Question 21

How can stem cells cure?

Answer 21

Stem cells transferred from the bone marrow of a healthy person can replace faulty blood cells.
Embryonic stem cells could make insulin-producing cells for people with diabetes or nerve cells for people paralysed by spinal injuries.

Question 22

What is therapeutic cloning?

Answer 22

When an embryo is made to have the same genetic information as the patient. This means that the stem cells produced from it would also contain the same genes and so wouldn’t be rejected by the patients body if used to replace faulty cells.

Question 23

Explain cloning in a plant.

Answer 23

In the right conditions, a plant cell will become unspecialised and undergo mitosis many times. Each of these undifferentiated cells will produce more cells by mitosis. Given different conditions, these will then differentiate to form tissues such as xylem, phloem, photosynthetic cells, and root hair cells that are needed to form a tiny new plant. The new plant will be identical to the original parent.

Question 24

What can clning plants be used for?

Answer 24

To grow more plants of rare species.
Grow crops of identical plants with desired features.

Question 25

Explain how and why you would expect the length of the cell cycle to vary between an early embryo and a 5 year old.

Answer 25

early embryo cell cycle very rapid with little time for growth stage 1 as short as possible as embryo forming new cells 5-year-old child cell cycle rapid as child growing quickly but not as fast as early embryo longer periods of growth between divisions

Question 26

Explain how and why you would expect the length of the cell cycle to vary between a 13 year old and a 70 year old.

Answer 26

13-year-old student cell cycle rapid as growth and development taking place during puberty requiring new cells 70-year-old adult cell cycle slow as new cells still needed for repair but not for growth cell death beginning to overtake cell division

Question 27

When is the cell cycle likely to be rapid in a human and when is it likely to be slow?

Answer 27

very rapid • at any time when rapid growth is needed • examples (embryonic development, childhood, puberty, pregnancy, after injury) relatively slow • throughout adult life (excepting pregnancy or injury) • in sports training • cell cycle slows with age