Gene Mutation and Activity of Protein

Question 1

When is a DNA sequence change pathogenic?

Answer 1

• deletions
• nonsense mutations
• frameshifts

Question 2

When is a missense mutation more likely to be pathogenic?

Answer 2

if it:

• affects a functionally important part of the protein
• if the amino acid is conserved over evolution, it is more likely to be important
• if amino acid substations are non-conservative (polar for non-polar, acidic for basic) they are more likely to be pathogenic

Question 3

What type of activity does ATM have?

Answer 3

kinase activity (phosphorylation)

Question 4

How can you measure the ATM kinase activity?

Answer 4

• use ionising radiation or radiometric drug to activate
• immunoprecipitate the ATM protein using an ATM Ab and use it to phosphorylate a protein target (p53) in vitro

or
-use phosphospecific antibodies to detect the phosphorylated target

Question 5

What is haploinsufficiency?

Answer 5

For most gene products half the amount of protein is sufficient for normal function. For some gene products 50% of the normal level is not enough for normal function and haploinsufficiency produces an abnormal phenotype

Question 6

What is a dominant negative effect?

Answer 6

A non-functional mutant polypeptide can interfere with a normal protein from the normal allele giving a dominant negative effect

Question 7

What prognosis do people have with no protein expression at all?

Answer 7

• associated with classical disease

- outlook for patient associated with classical prognosis

Question 8

What prognosis do people have with some protein expression?

Answer 8

• may be associated with a less severe picture
• difficult to suggest to a patient that this will mean a better outlook even if this is suggested by residual protein function