B12

Question 1

Genome

Answer 1

The entire set of genetic material in tan organism

Question 2

Human genome uses

Answer 2

Allows scientists to identify genes in the genome that are linked to different types of disease, knowing these help us develop effective treatments for them
Can trace the migration of certain populations of people around the world. Different populations of people developed tiny differences in their genomes when they migrated away from Africa, which can be investigated using genomes.
Can make many different proteins from the same gene by using it in different ways , or by switching part of a gene on and off

Question 3

Where do you inherit your mitochondrial DNA from?

Answer 3

Your mother, because it comes from the mitochondria in the egg

Question 4

Disadvantages of human genome

Answer 4

Understanding it has taken years of work and billions of pounds

Question 5

Where does meiosis occur in humans?

Answer 5

Only in the reproductive organs(ovaries in females and testes in males)

Question 6

Process of meiosis

Answer 6

1) Before the cell begins to divide, it duplicates its genetic information, forming two armed chromosomes which then arrange themselves into pairs.
2) In the first division in meoisis the chromosome pairs line up in the centre of the cell.
3) The pairs are pulled apart so each new cell only has one copy of each chromosome.
4) In the second division, the chromosomes line up again in the centre of the cell. The arms of the chromosomes are pulled apart.
5) You get four gametes, each with only a single set of chromosomes in it. Each of the gametes is genetically different from the others, since chromosomes are shuffled up in meiosis and each gamete only gets half of them, at random.

Question 7

What happens to the cell produced by gamete fusion?

Answer 7

1) After two gametes have fused during fertilisation, the resulting new cell divides by mitosis to make a copy of itself.
2) Mitosis repeats many times to produce lots of new cells in an embryo.
3) As the embryo develops, these cells start to differentiate into the different types of specialised cell that make up a whole organism.

Question 8

Which pair of chromosomes decides sex?

Answer 8

The 23rd pair - labelled XY(male) or XX(female)

Question 9

Which chromosome causes male characteristics?

Answer 9

The Y Chromosome

Question 10

Which chromosome causes female characteristics?

Answer 10

The X Chromosome

Question 11

What happens to the X and Y chromosomes when making sperm?

Answer 11

When making sperm, the X and Y chromosomes are drawn apart in the first division in meiosis. There’s a 50% chance each sperm cell gets an X-chromosome and a 50% chance it gets a Y-chromosome.

Question 12

Characteristics controlled by a single gene

Answer 12

Mouse fur colour
Red-green colour blindness in humans

Question 13

How many alleles of every gene in your body do you have?

Answer 13

You have two alleles of every gene in your body - one on each chromosome in a pair

Question 14

Cystic fibrosis

Answer 14

A genetic disorder of the cell membranes. It results in the body producing a lot of thick sticky mucus in the air passages and in the pancreas. Caused by a recessive allele

Question 15

Polydactyly

Answer 15

A genetic disorder where a baby’s born with extra fingers or toes - but isn’t life-threatening. Is caused by a dominant allele.

Question 16

Emrhyonic screening

Answer 16

Involves undergoing tests to discover if a person/embryo/foetus has a genetic disorder or is carrying a faulty allele

Question 17

Disadvantages of embryonic screening

Answer 17

1)Is expensive.
2) Maybe everyone may want to screen their embryos so they can pick the most ‘desirable’ one e.g. they want a blue-eyed, blond-haired, intelligent boy.
3) An IVF embryo(a potential life) might be destroyed if alleles causing a genetic disorder are found in its genes
4) Tests might not be reliable

Question 18

Advantages of embryonic screening

Answer 18

1) Helps stop people suffering.
2) Treating disorders costs the Government(and the taxpayer) a lot of money.
3) There are laws to stop it going too far. At the moment, parents can’t even select the sex of their baby(unless it’s for health reasons).

Question 19

Genetic screening methods

Answer 19

Amniocentesis
Chorionic villus sampling
Analysing foetal cells found in the mother’s bloods

Question 20

Pre-natal testing

Answer 20

Used to analyse an individual’s DNA or chromosomes before they’re born, can’t detect all inherited disorders

Question 21

Neo-natal testing

Answer 21

Used just after a baby has been born, designed to detect genetic disorders that can be treated early

Question 22

How many base pairs/genes are in the human genome?

Answer 22

The human genome contains over 3 billion base pairs and almost 21000 genes that code for proteins.

Question 23

Evidence of two organisms being the same species

Answer 23

Similar genotype/DNA
Same/similar phenotype
Can breed and produce fertile offspring

Question 24

organisms involved in asexual reproduction

Answer 24

Bacteria
Strawberry plant
Daffodils
Smallest plants

Question 25

Organisms reproducing sexually and asexually

Answer 25

Malarial parasites produce asexually in the human host, but sexually in the mosquito.
Many fungi reproduce asexually by spores, but also reproduce sexually to give variation.
Many plants produce seeds sexually, but also reproduce asexually by runners such as strawberry plants, or bulb division such as daffodils.
Daffodils reproduce asexually, growing from bulbs. New bulbs can grow from the main one, producing a new identical plant.

Question 26

Advantage of organisms reproducing sexually and asexually

Answer 26

It means plants can reproduce even if the flowers have been destroyed by frost or other animals

Question 27

Where does mitosis occur?

Answer 27

All body cells except gametes

Question 28

When sperm and egg cells fertilise to produce a new cell, how many chromosomes are in that new cell?

Answer 28

46

Question 29

Fusion of gametes in plants(sexual reproduction)

Answer 29

Sex cells fertilise to form a seed