Edexcel A-Level Biology AS 2.16 Cystic Fibrosis Gene Mutation Effects Questions

*8(a)(ii)

Indicative content:

Descriptions of diagrams (D points)

- reduced diameter of lumen (in person with CF)

- thicker or inflamed muscle layer (in person with CF)

- more mucus (in person with CF)

Cystic fibrosis (C points)

- CF results in the production of very \{sticky / thick\} mucus (credit this point only once)

- CF is due to a \{mutation in the CFTR gene / faulty CFTR allele\}

- (resulting in) \{the CFTR protein not functioning properly / abnormal or defective CFTR protein / abnormal channel proteins / CFTR channel blocked\}

- this affects transfer of chloride ions out of cells

- ( $\mathrm{Cl}^{-}$accumulate in cells so) \{water moves out of mucus / water remains in cytoplasm\} / mucus is dehydrated \}

Change in lumen diameter (L points)

- CF results in the production of very \{sticky / thick\} mucus (credit this point only once)

- diameter of lumen in patient with CF is reduced

- because the mucus builds up

- (because the) cilia cannot move / beat (idea of cilia normally clearing mucus)

- (because the) cilia cannot move mucus away (it is too thick) (credit this only once)

- Inflammation of muscle (narrows lumen) (credit this only once)

Inflammation (I points)

- cilia cannot move mucus away (it is too thick) (credit this only once)

- mucus (is very sticky and) traps bacteria

- bacteria have ideal growth conditions (in mucus)

- bacteria can cause (chest) infections

- CF characterised by coughing \{to remove mucus / as a result of infection\}

- \{coughing / infection\} damages \{cells / tissues\} (lining airways)

- (leading to) inflammation of muscle (credit this only once)

(6)

Level

Marks

0

No awardable content

1

1-2

Level 1: description of diagrams

1 mark: one D or one C point

2 marks: second D or C point

2

3-4

Level 2: explanation of either change in diameter of lumen or inflammation linked to CF

3 marks: three L points or 3 I points

4 marks: as 3 marks plus additional C point

3

5-6

Level 2: explanation of both change in diameter of lumen and inflammation linked to CF

5 marks: three L points and 3 I points

6 marks: as 5 marks plus additional C point