B13

Question 1

Asexual reproduction (4 points)

Answer 1

One parent only
Cell divison by mitosis
Offspring are clones
Body cells reproduce asexually to replace worn out tissues

Question 2

Sexual reproduction

Answer 2

Need 2 parents (male amd female)
Gametes fuse to form a zygote
Gametes formed by meiosis

Question 3

Gametes in plants

Answer 3

Female-egg cell

Male-pollen

Question 4

Gametes in animals

Answer 4

Female-egg cells

Male-sperm

Question 5

What happens to chromosomes in meiosis?

Answer 5

Halved

Question 6

Explain meiosis

Answer 6

1) all chromosomes copied
2) cell divides in 2
3) both cells divide again forming 4 gametes

Question 7

What happens after fertilisation?

Answer 7

Zygote divides by mitosis to develop into embryo then foetus then baby

Question 8

Advantages of asexual reproduction

Answer 8

Only need one parent
No need to make gametes
Faster
Used for selective breeding

Question 9

Disadvantages of asexual reproduction

Answer 9

No variation

If one clone cant survive none can

Question 10

Advantages of sexual reproduction

Answer 10

Produces variation
Survival advantage
Selective breeding

Question 11

Disadvantages of sexual reproduction

Answer 11

Takes time and energy
Have to find a mate
Have to make and spread gametes
Slow

Question 12

How do flowers sexualy reproduce?

Answer 12

Gametes produced by meiosis
Pollen reaches egg cells of plant
Pollen fuses with egg cell to form seed

Question 13

How do flowers asexually reproduce?

Answer 13

Produce runners
Runners touch soil
Plnt is developed

Question 14

When does malaria asexually reproduce?

Answer 14

In the host(human)

Question 15

When does malaria sexually reproduce?

Answer 15

In mosquito

Question 16

What are genes?

Answer 16

Small section of DNA that codes for a protein

Question 17

What is DNA made up of?

Answer 17

Monomers called nucleotides

Question 18

What is a nucleotide made of?

Answer 18

A sugar
A phosphate
A base

Question 19

How is a polynucleotide formed?

Answer 19

The phosphate of one nucleotide is formed to the sugar of another nucleotide.

Question 20

How do genes code for proteins?

5

Answer 20

1) one strand of dna copied and used to make mRNA
2) mRNA leaves nucleus and binds to a ribosome
3) tRNA with a complementary base pair with mRNA joins together to form a specific protein
4) tRNA detaches from amino acids and mRNA
5) protein change folded into a specific shape that allows it to carry out its function

Question 21

What does it mean when a gene is expressed?

Answer 21

Ot is synthesised in the cell

Question 22

What is a mutation?

Answer 22

A change in the sequence or amount of DNA.

Question 23

What are the effects of a mutation?

Answer 23

Change in shape of the protein
Causes protein to be weaker or stronger
Active site not to bind to substance efficiently
Affects which genes are switched on or off

Question 24

2 inherited disorders

Answer 24

Polodactylyl

Cystic fibrosis

Question 25

How to cure cystic fibrosis?

Answer 25

Replace faulty gene with a healthy one | Gene therapy

Question 26

What is amniocentesis?

Answer 26

Carried out in week 15 of pregnancy Amniotic fluid removed from fetus Contains fetal cells that can be analysed

Question 27

What is Chorionic vilus sampling?

Answer 27

Betwwen week 10and12 Small sample of tissue taken from placenta Risk of miscarriage

Question 28

Problems with embryo screening? | 4

Answer 28

Posibility of false positives Chance of miscarriage Emotional effects Expensive