Cell division and growth

Question 1

why are new cells needed?

Answer 1

they are needed for growth and repair of damaged cells

Question 2

what must new cells have?

Answer 2

they must have the same genes as the original

Question 3

what is a chromosome?

Answer 3

a long thread like structure in the nucleus made of DNA, they carry the genes
humans have 23 pairs

Question 4

what is DNA?

Answer 4

it is a chemical that carries the genetic codes and makes up chromosomes

Question 5

what is a gene?

Answer 5

parts of your DNA hat tells the cell how to make a type of protein

Question 6

what is an allele?

Answer 6

different version of the same gene

Question 7

how many chromosomes do the body cell contain?

Answer 7

46 chromosomes 
23 pairs ( one from each parent )

Question 8

how many chromosomes do gametes contain?

Answer 8

23

Question 9

How do cell become specialised?

Answer 9

sperm and egg meet
fertilisation 
zygote forms
cell division
CELL BECOMES SPECIALISED

Question 10

what needs to happen for an organism to grow?

Answer 10

cells need to multiply

Question 11

describe the process of mitosis

Answer 11

1. thin strands of DNA in the nucleus of the parent cell thicken to form chromosomes
2. the chromosomes make copies of themselves
3. the nuclear membrane starts to break down
4. the copied chromosomes line up in the centre of the cell
5. half of the chromosomes are pulled to opposite sides of the cell.
6. the cell membrane starts to pinch at the centre
7. new nuclear membrane form around the chromosomes
8. two identical daughter cells are formed.

Question 12

what is mitosis?

Answer 12

its when identical copies of the original cells are made

it is for the growth and repair of cells and tissues.

Question 13

describe the process of meiosis

Answer 13

1. the cell duplicates its DNA
2. identical chromosomes line up in the cells centre
3. chromosomes separate
   4 splits into two producing two cells with different chromosomes
4. the chromosomes separates for a second time
   you are left with four egg cells each one contains
   23 pair of chromosomes

Question 14

what is meiosis?

Answer 14

the production of cells which have half the normal number of chromosomes
- these are called gametes ( sex cells )

Question 15

explain the process of fertilisation

Answer 15

1. during sexual reproduction the sex cells ( gametes) combine to form a new individual
2. gametes only have 23 chromosomes therefore when they combine you get 46 chromosomes.
3. the new individual will have a mixture of the set of features from both parents (Variation)

Question 16

what are stem cells?

Answer 16

stem cells are cells that can turn into any different type of cells,if given the right instructions.

Question 17

where can they be found?

Answer 17

• early human embryos
• umbilical cord
• adult bone marrow

Question 18

what can they be used for?

Answer 18

in medicine to…

• treat blood diseases (sickle cell anaemia)
• replace faulty cells in sick people ( insulin producing cells, nerve cells)

Question 19

Points against stem cell research

Answer 19

• embryos are potential human life
• curing patients that are already exist is more important
• scientists should concentrate on finding and developing other sources of stem cells
• embryos cannot give permission
• patients may develop cancer when being treated using stem cells

Question 20

what are stem cells in plants called?

Answer 20

meristem cells

Question 21

what is a dominant allele?

Answer 21

when you only need one allele to show the dominant characteristic (represented by CAPITAL LETTER)

Question 22

what is a recessive allele?

Answer 22

when you need two alleles for the characteristic to be recessive(represented by a lower case letter)

Question 23

define hetrozygous

Answer 23

if the two alleles for a particular gene are different then it is referred to as hetrozygous

Question 24

define homozygous

Answer 24

if the two alleles for a particular gene are the same then it is referred to as homozygous

Question 25

what is the shape of DNA?

Answer 25

a double helix structure