B5

Question 1

Gametes?

Answer 1

one type of cell where the chromosomes are not paired. For example, in humans the gametes are sperm and egg cells

Question 2

How are gametes made?

Answer 2

By a type of cell division called meiosis

Question 3

fusion?

Answer 3

joining e.g. sexual reproduction involves fusion of male and female gametes

Question 4

What happens in asexual reproduction?

Answer 4

There is only one parent therefore it does not involve Gametes. there is also no mixing of genetic information due to there only being one parent, so all offspring are identical

Question 5

where is the only place that meiosis takes place?

Answer 5

reproductive organs e.g. testes and ovaries

Question 6

meiosis?

Answer 6

cells very carefully count and divide their chromosomes so that each gamete has exactly 23 chromosomes. Then when an egg with its 23 chromosomes is fertilized by a sperm with its 23 chromosomes, the resulting fertilized egg has exactly 46 chromosomes.

Question 7

Fertilisation?

Answer 7

gametes joining together in sexual reproduction

Question 8

What has happened to the cells due to fertilisation?

Answer 8

The cell now has the normal number of chromosomes

Question 9

What happens after fertilisation?

Answer 9

The new cell divides by mitosis to produce a clump of identical cells (embryo)

Question 10

What happens as the embryo develops?

Answer 10

the cells differentiate forming different cell types e.g. muscle cells, brain cells

Question 11

What does our DNA determine?

Answer 11

our inherited features

Question 12

What is a key feature of DNA?

Answer 12

has two polymers forming a double helix

Question 13

Gene?

Answer 13

Small section of DNA on a chromosome

Question 14

Genome?

Answer 14

The entire genetic material of an organism

Question 15

3 reasons why is it good that scientists have studied the entire human genome?

Answer 15

1) help us to search for genes that are linked to a disease

2) help us to understand and treat inherited disorders

3) helps to discover ancestry

Question 16

How many copies of each gene do we have?

Answer 16

2

Question 17

Alleles?

Answer 17

Versions of a gene

Question 18

Genotype?

Answer 18

Tells us the alleles present

Question 19

Homozygous?

Answer 19

The person has got two copies of the same allele e.g. EE or ee

Question 20

Phenotype?

Answer 20

tells us the characteristics caused by the persons alleles

Question 21

Heterozygous?

Answer 21

The person have two different alleles
e.g. Ee or Dd

Question 22

What phenotype will a person with heterozygous have?

Answer 22

The dominant allele e.g. polydactyly e.g. not cystic fibrosis

Question 23

Recessive allele?

Answer 23

Will only show in the phenotype if two copies are present e.g. the other allele is dominant

Question 24

What is Cystic fibrosis?

Answer 24

a disorder of cell membranes

Question 25

Is a defective cell membrane dominant or recessive?

Answer 25

recessive, therefore, in order to have cystic fibrosis, the person has to have two copies of the defective allele (both parents have to have it)

Question 26

What happens if a cystic fibrosis person has a Cc allele?

Answer 26

They are a carrier

Question 27

what is wrong with people that have polydactyly?

Answer 27

extra fingers or toes

Question 28

What happens if on of the embryo’s parents has a dominant allele of polydactyly?

Answer 28

They will have the disorder because polydactyly is a dominant allele

Question 29

Embryo screening?

Answer 29

embryos are tested to see if they have the alleles for inherited disorders

Question 30

2 problems with embryo screening?

Answer 30

Expensive - ppl say it should be spent elsewhere in the health service

the best embryo is chosen and the rest are destroyed - healthy or unhealthy, therefore ppl say it is unethical

Question 31

What could happen in the future with embryo screening?

Answer 31

May be able to screen embryos to produce offspring with desirable features e.g. taller, intelligent

Question 32

What is the person called if they only have one allele of cystic fibrosis?

Answer 32

A carrier

Question 33

What is the chance that 2 people who are carriers of cystic fibrosis have a baby which has the disorder?

Answer 33

25%

Question 34

What sex chromosomes do males have?

Answer 34

XY

Question 35

What sex chromosomes do females have?

Answer 35

XX