T2L9 Mutations and CF

Question 1

Explain the genetic cause of cystic fibrosis (10)

Answer 1

• A mutation is a change in the sequences in a gene
• This occurs in DNA during DNA replication
• This means that during protein synthesis, the mRNA transcribed from the DNA will have the mutation
• The ribosome will then match the wrong tRNA anticodon to the mRNA codon
• Therefore the wrong amino acid will be added to the polypeptide chain
• The protein’s primary structure will be wrong
• This means that the wrong bonds will form and the protein will not fold correctly in its tertiary structure
  -This means the shape of the protein will be wrong and so it cannot carry out its function (of transporting chloride ions across the membrane)
• The gene codes for the CFTR protein
• In CF patients the CFTR protein is missing/ in smaller number/ non-functional
• The protein’s job is to allow Cl- ions put of epithelial cells
• In CF patients the ions don’t leave the cells
• This means water isn’t drawn out of epithelial cells
• So mucus remains thick ad sticky
• Thick mucus causes symptoms

Question 2

Name 5 types of mutation

Answer 2

• Translocation
• Deletion
• Duplication
• Inversion
• Insertion

Question 3

Describe a deletion mutation

Answer 3

When a section of the chromosome/gene is missing

Question 4

Describe a duplication mutation

Answer 4

When a section of genetic code is repeated within the chromosome

Question 5

Describe an inversion mutation

Answer 5

The genetic information in part of a chromosome is in reverse order

Question 6

Describe an insertion mutation

Answer 6

Part of one chromosome is inserted into another chromosome
e.g
111122223333
44445555
goes to

1111223333
4444225555

Question 7

Describe a translocation mutation

Answer 7

When two different chromosomes have exhanged pieces

Question 8

Demonstrate the affect of missing bases

Answer 8

AAC CAA TGC CAT
AAC CAA CAT
this would mean a whole amino acid would be missing from the polypeptide chain

or

AAC CAA TGC CAT
AAC CAT GCC AT-

in this case the second A of CAA is missing. This means that not only would one amino acid change - but so would all of the following ,utations TGC has become GCC and this may or may not code for a different polypeptide chain