Molecular Diagnosis 3

Question 1

DNA sequencing ethics

Answer 1

• does it open up areas for discrimination e.g. Insurance companies
• who owns the DNA sequence?
• can the knowledge prevent illness in later life?

Question 2

Southern hybridisation (for DNA)

Answer 2

• uses an allele-specific probe

- mismatch of primer sequence to DNA sequence at 3’ end doesn’t allow for binding there - TAC polymerase can not work

Question 3

Northern hybridisation (analysis of RNA)

Answer 3

• RNA degrades more easily that DNA

Question 4

Reverse transcriptase PCR (RT-PCR)

Answer 4

mRNA has a long PolyA tail (AAAA) which the primer is complimentary to (TTTT)
once a cDNA is made the mRNA is degraded leaving just a single stranded DNA
The DNA can be used as a template for PCR

RT-PCR can also stand for real time PCR

Question 5

Microarray technology

Answer 5

(Don’t have to know which gene you are looking for)
Analysis of 1000s of genes - “genome wide analysis”
Allocate either green/red dye for control and the other for the diseased patient (need to have a comparison)

Question 6

DNA fingerprinting

Answer 6

‘Minisatellites’ - repeated sequences (different amounts for each individual)
- shows a family relationship
‘Small tandem repeats (STR)’ - smaller number of repeating sequences

Question 7

Chromosome analysis - karyotyping

Answer 7

• chromosome banding in specific chromosomes is the same unless there is a problem
• FISH (fluorescence in situ hybridisation) - to detect abnormal genes
• chromosome painting - “family of probes” specific to one specific chromosome. In diseased states e.g. Tumours then one chromosome has a variety of colours - chromosome translocation

Question 8

Sanger chain termination method

Answer 8

Uses labelled nucleotides