DNA probes - locating genes, screening

Question 1

What is a DNA probe

Answer 1

• Single strand of DNA
• its base sequence is complementary to the base sequence of the gene its designed to identify

Question 2

What are DNA probes used for

Answer 2

To locate specific alleles of genes and to screen patients for heritable conditions, drug reinsert o health risks

Question 3

How are DNA probes able to locate specific alleles

Answer 3

• DNA probes are created to have a complementary base sequence to the alleles that is being screened for
• patients DNA is treated to make it single stranded and is then mixed with DNA probes
• if the patient has the alleles then the DNA probe will hybridise and the label indicates the presence

Question 4

Describe DNA hybridisation

Answer 4

• patients DNA heated to make it single stranded
• heat causes the hydrogen bonds between bases to break, denaturing them
• patients single stranded DNA sample is mixed with the DNA probe, cooled, and complementary bases can align and form hydrogen bonds (anneal)
• some patients DNA samples will anneal back together and some will anneal with the DNA probe

Question 5

Describe how DNA probe can locate specific alleles

Answer 5

• to locate a specific allele the DNA base sequence must be known to then relate the DNA probe
• this can be determined using DNA sequencing techniques
• fragment of DNA an be produced using a gene machine
• fragment can be amplified using PCR
• label is added eg fluoresent marker genes
• after hybridisation, the DNA is washed so that any unbound DNA probes are washed away
• presences of fluorescence label indicates alleles of interest is present on patients DNA

Question 6

What is gentics screening

Answer 6

Uses DNA sequencing, probes and hybridisation to diagnosis individuals

Question 7

Application of DNA probes

Answer 7

• to screen someone’s DNA for a particular heritable health condition
• identify gene for use in genetic engineering
• to predict how someone will respond to a drug