B2-Cell Division

Question 1

A gene is

Answer 1

A section of a chromosome and a section of DNA

Question 2

DNA (deoxyribonucleic acid)

Answer 2

• double helix structure (twisted ladder)
• the rungs of the ladder are called bases
• > this is the genetic code

Question 3

Mitosis is

Answer 3

the process of one set of chromosomes is pulled to each end of the dividing cell and the nucleus divides.

Question 4

Stage 1

Answer 4

• the longest stage in the cell cycle
• cells grow bigger, increase their mass, and carry out normal cell activities
• replicate their DNA to form 2 copies of each chromosome ready for cell division
• increase number of sub-cellular structures e.g. mitochondria, ribsomes and chloroplasts (ready to divide)

Question 5

Stage 2

Answer 5

Mitosis is the start of cell division

• the copied chromatids line up along the centre of the cell
• nucleus ‘disappears’
• start to separate as they are pulled into different halves of the cell

Question 6

Stage 3

Answer 6

The cytoplasm and the cell membrane also divide into two identical daughter cells as the nucleus has reformed around each set of chromosomes

Question 7

Differentiation

Answer 7

The process that cells take on specific roles ‘specialisation’

Question 8

A stem cell is

Answer 8

Early development of animal and plant embryos, the cells are unspecialised so they can become any type of cell that is needed

Question 9

An adult stem cell is an

Answer 9

undifferentiated cell of an organism that can give rise to many more cells of the same type and is differnt to embryonic stem cells.

Question 10

Blastocyst

Answer 10

A thin-walled hollow structure in early embryonic development that contains a cluster of cells called the inner cell mass from which the embryo arises.

Question 11

Where to get stem cells from

Answer 11

Sperm+ovum=zygote->early stage embryo->late stage embryo-> fetus (early and late stage embryo contain stem cells)

Question 12

Where stems cells would be found in a human and a plant

Answer 12

Human= bone marrow
Plant= meristems

Question 13

Write a clearly balanced account of the arguments surrounding embryonic stem cell research

Answer 13

Embryonic stem cells could be used to cure incurable diseases like diabetes and Parkinson’s. But there is a cost that an embryo could become human life and this is therefore destroying human life (murder). It does have a huge potential and the church believes there are the same issues as with abortion when new life begins. Although why is their a public fear around stem cells when abortion and contraceptive pills are allowed. Also the people discussing this are healthy and do not suffer from the serious illnesses and deterioration of people suffering even at a young age. But they can get stem cells from IVF treatment with left over embryos that would be thrown away or frozen forever. So for me that resolves all the issues around stem cells as well as it should be the patients choice to choose.

Question 14

Emryonic stem cells vs adult stem cells

Answer 14

Embryonic:
-can give rise to all types of cells (undifferentiated)
-plentiful in embryos (and umbilical cord blood)
-ethically/legally controversial
Adult
-Can only give rise to a limited number of cell types e.g. stem cells in bone marrow can form all the blood cells but no other cell type
-hard to find and isolate
-ok

Question 15

Differentiation in plants

Answer 15

• Plants continue to grow throughout their lives
• plants are able to differentiate there whole life
• undifferentiated cells formed at active regions of the stem and roots known as meristsems
• plants only differentiate when they are in there final position in a plant
• in meristems mitosis takes place continuously the cells then elongate and grow before they finally differentiate

Question 16

Differentiation in plants 2

Answer 16

Differentiation means in the right conditions a plant will become unspecialised, undergoing mitosis many times and will create the right cells to form a tiny new plant.
Cloning many individual plants is an advantage in plant research as they produce large amonuts of identical plants for research.
It could save rare species by producing large amounts of rare plants reliably and safely by cloning and is quick + economical.

Question 17

Cloning

Answer 17

Producing identical offspring

Question 18

Advantages of cloning

Answer 18

in plant research as they produce large amonuts of identical plants for research.It could save rare species by producing large amounts of rare plants reliably and safely by cloning and is quick + economical.