7: DNA analysis

Question 1

What is penetrance?

Answer 1

The likelihood you will have a disease if you have a gene mutation

Question 2

What is a Mendelian disease?

Answer 2

High penetrance, low prevalence disease

Question 3

What are some advantages of NGS?

Answer 3

Allows you to look at

a) more genes

b) faster

than conventional sequencing

Question 4

What is the coverage of genetic sequencing?

Answer 4

How much of the gene you’ve actually looked at

Question 5

What are the three possibilities in the outcome of a gene mutation?

Answer 5

Harmful mutation

Harmless polymorphism

Variant of unknown significance (you can’t tell either way)

Question 6

How many polymorphisms does the average person have?

Answer 6

3 million

1 or 2 of which could be the disease causing mutations

So the results of sequencing need to be filtered

Question 7

What percentage of the genome is made up of exons?

Answer 7

1 - 2%

Called the exome

Question 8

SMAD4:p.Arg157Ile

means that in the gene SMAD4, the Arginine at position 157 has mutated to an Isoleucine

position 1 is always a methionine

this is describing the RNA chain

Question 9

SMAD4:p.Cys162Ter

In SMAD4 gene, the cysteine at position 162 has mutated into a stop

this is describing the RNA chain

Question 10

In a situation where a patient has lots of variations and you’re unsure which is the disease causing mutation, what do you do?

Answer 10

Look at patient phenotype

Question 11

Mendelian disorders are low ___, high ___.

Answer 11

low frequency

high prevalence

Question 12

Multifactorial disorders are low ___, high ___.

Answer 12

low penetrance

high frequency

Question 13

What is the best genetic test for multifactorial heart disease?

Answer 13

Blood cholesterol

Question 14

What is the prevalence of long QT syndrome?

Answer 14

1 in 2000

so fair likelihood that each GP practice will have one