Week 8 Genetics - molecular testing Flashcards Preview

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Flashcards in Week 8 Genetics - molecular testing Deck (10):
1

What does molecular genetics look for?

Molecular genetic change that explains disease. Typically DNA based testing

2

Explain Sanger sequencing

-DNA polymerases copy single stranded DA templates by adding nucleotides to a growing chain
- DNA Polymerases can also incorporate analogues of nucleotide bases. Sanger sequencing uses 2,3-dideoxynucleotides as substrates, which may be fluorescently labelled. When these are incorporated at the 3' end of the growing chain, chain elongation is terminated selectively at A, C, G or T - this is because once the deoxynucleotide is incorporated, there is no 3'-hydroxyl group, preventing further elongation
-The resulting fragments are then put together to reveal the sequence of the original piece of DNA
-The fluorescent ddNTPs can then be run through capillary electrophoresis, which output data as coloured peaks, depicting the DNA sequence

3

If a mutation is recessive, what is the likely outcome for the protein?

Reduced, or no function
Mutation is usually nonsense, missense, frameshift or a splicing variant

4

If a mutation is dominant, what is the likely outcome for the resulting protein?

New, abnormal function, unless dominant negative
Mutation is usually missense

5

What is a synonymous molecular change?

No change to the protein, but changes in binding sites for enhancer or suppressor proteins

6

What is a dynamic mutation, and which two disease have this?

An increase or decrease in naturally occurring repetitive sequences of codons.
Disorders include Huntingtons and fragile X

7

What is a disorder of imprinting?

Prader-Willi

8

What does p.Ala479Pro describe?

Alanine was the original amino acid, that was changed to a proline, at codon position 479 in the reference sequence

9

What does p.[(Tyr63*)];[0] mean?

At codon position 63 of the reference sequence, the codon for a Tyrosine has been changed to a stop codon - this is represented by the star.
The [0] represents that this must have occurred on an X chromosome, and the subject is a man

10

In which two scenarios can a mutation appear homozygous, when it's actually not?

-X-linked disorder in a man
-A gene has been deleted from the other chromosome

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