B6 Inherited Disorders (page 74)

Question 1

What is meant by Interited Disorders?

Answer 1

you can inherit some disorders from your parents.

Many of these can be screened for in embryos.

Question 2

What is Cystic Fibrosis?

Answer 2

it is 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.

Question 3

What is Cystic Fibrosis caused by?

Answer 3

a Recessive Allele.

Question 4

Look at diagram 1 on page 74, The allele which causes cyctic fibrosis is a what? allele?

Answer 4

is a recessive allele. ‘f’, Because it’s recessive, people with only one copy of the allele won’t have the disorder - they’re known as carriers.

carried by about 1 person in 25

Question 5

For a child to have cystic fibrosis, how many parents must be carriers, or have the disorder themselves?

Answer 5

both parents must be either carriers or have the disorder themselves for the child to have cystic fibrosis.

Question 6

What chance do the child have of having cystic fibrosis looking at diagram 1 on page 74?

Answer 6

There’s a 1 in 4 chance of a child having the disorder if both parents are carriers.

Question 7

What is Polydactyly?

Answer 7

it is a genetic disorder where a baby’s born with extra fingers or toes.

(it doesn’t usually cause any other problems so isn’t life-threatening.

Question 8

What is Polydactyly caused by?

Answer 8

a Dominant Allele ‘D’, and so can be inherited if just one parent carries the defective allele

The parent that has the defective allele will have the condition too since the allele is dominant.

Question 9

Look at diagram 2 on page 74, and explain what percentage chance the child has of having Polydactyly disorder if one parent has one D allele?

Answer 9

50% chance of a child having the disorder.

Question 10

During In Vitro Fertilisation (IVF), what happens?

Answer 10

The embryos are fertilised in a laboratory, and then implanted into the mother’s womb.

Question 11

Before embryos are implanted into the mother’s womb, is it possible to remove a cell from each embryo and analyse its genes?

Answer 11

Yes

Question 12

Why can embryos genes be analysed before being implanted into the mother’s womb?

Answer 12

Many genetic disorders can be detected in this way, such as cyctic fibrosis.

It is als possible to get DNA from an embryo in the womb and test that for disorders.

Question 13

Embryonic screening is quite controversial, why?

Answer 13

because of the decisions it can lead to.

For embryos produced by IVF - after screening, embryos with ‘bad’ alleles would be destroyed.

For embryos in the womb - screening could lead to the decision to terminate the pregnancy.

Question 14

There are lots of ethical, social and economic concerns surrounding embryo screening.

Give some examples ‘Against Embryonic Screening’?

Answer 14

1) It implies that people with genetic problems are ‘undesirabe’ - this could increase prejudice.

2) There may come a point where everyone wants to screen their embryos so they can pick the most ‘desirable’ one, e.g. they want a blue-eyed, blond-haired, intelligent boy.

3) Screening is expensive.

Question 15

Give some examples of people ‘For Embryonic Screening’?

Answer 15

1) It will help to stop people suffering.

2) Treating disorders costs the Government (and the taxpayers) a lot of money.

3) There are laws to stop it going too far. At the moment parents cannot even select the sex of their baby (unless it’s for health reasons).

Question 16

Why won’t someone heterozygous for the cystic fibrosis allele have the disorder (3 marks)?

Answer 16

Because the allele which causes cystic fibrosis is recessive (1 mark), so you have to have two recessive alleles to have the disorder (1 mark), Heterozygous people have one dominant and one recessive allele (1 mark).