DNA Probes and Hybridisation

Question 1

dna probe

Answer 1

short, single stranded length of DNA that has a label attached to it
is complementary to a specific base sequence
used to locate specific alleles
radioactive- nucleotides contain isotope 32
probe is identified using X ray film that is exposed using radioactivity
fluorescent- emit fluoresence under certain conditions- when probe is bound to target dna sequence

Question 2

DNA hybridisation

Answer 2

dna extracted from cell sample
heated to break h bonds and form single stranded dna
mixed with dna probe
cooled to allow complementary sequences to bind + h bonds to form
probes can be identified
dna is washed to remove any unbound dna

Question 3

locating specific alleles

Answer 3

cell sample taken from patient
dna extracted and amplified using PCR
add restriction enzymes to cut the dna
separate fragments using gel electrophoresis
put on nylon and add alkali to make single strands
label (probe) is added to base sequence of dna (comp to mutated allele)
after hybridisation dna is washed to remove unbound dna
presence of probe eg fluorescent/radioactive indicated the allele is present
autoradiograph (x ray)

Question 4

genetic screening

Answer 4

can fix lots of dna to an array and any complementary dna sequences will bind to probe
can test simultaneously for different genetic disorders

Question 5

personalised medicine

Answer 5

advice can be given based on a person’s genotype
some drugs will be more or less effective depending on genotype
pain medications require specific enzyme to be activated to function effectively
half of population have genes that alter the function of this enzyme
screening for gene ensures correct dose/ type is given