gene technology

Question 1

what is a DNA probe

Answer 1

a short section of DNA with a known base sequence, that is complimentary to a specific gene and fluorescently/ radioactively labelled

Question 2

describe a radioactive label

Answer 2

• made up of nucleotides with isotope P32
• probe identified using x-ray film that is exposed by radioactivity

Question 3

describe a fluorescent label

Answer 3

emit light under certain conditions e.g. when probe has bound to the target DNA sequence

Question 3

how does a dna probe identify a specific gene

Answer 3

• double stranded DNA being tested is treated to separate strands.
• strands mixed with probe binds to comp sequence on one of the strands- DNA hybridisation
• the site where the probe binds can be identified

Question 4

describe DNA hybridisation

Answer 4

• section of DNA or RNA is combined with a single stranded section of DNA that has comp bases.
• DNA must be single stranded so must be separated by heating DNA.
• when DNA cooled, the comp bases can anneal with each other or another comp strand

Question 5

what is step 1 of locating specific alleles on genes

Answer 5

the sequence of nucleotide bases of the mutant/target allele, must be determined.
- achieved using DNA sequencing techniques

Question 6

what is step 2 of locating specific alleles on genes

Answer 6

a fragment of DNA is produced that has sequence of bases that r comp to the target allele

Question 7

what is step 3 of locating specific alleles on genes

Answer 7

DNA probe is made by attaching a marker to the DNA fragment - made by fluorescent dye

Question 8

what is step 4 of locating specific alleles on genes

Answer 8

PCR used to produce multiple copies of the DNA probe

Question 9

what is step 5 of locating specific alleles on genes

Answer 9

DNA from person is heated to seperate the 2 strands

Question 10

what is step 6 of locating specific alleles on genes

Answer 10

the probe is mixed with DNA and mixture is cooled

Question 11

what is step 7 of locating specific alleles on genes

Answer 11

if person has target allele then DNA fragment will have the comp base sequence and DNA probe will be able to bind

Question 12

what is step 8 of locating specific alleles on genes

Answer 12

DNA is rinsed with water to clear any unattached probes

Question 13

what is step 9 of locating specific alleles on genes

Answer 13

any remaining DNA probes on fragment will be possible eto distinguish e.g. if fluorescent label used, light shining onto fragments cause them to fluoresce - observed under special microscopes

Question 14

describe DNA microarray

Answer 14

• label attached to human DNA
• test multiple alleles/mutations at once
• many DNA probes attached to a tile in a grid, in known positions
• patients labelled DNA is added
• DNA will hybridise to comp DNA
• rinse then view labels

Question 15

describe genetic screening

Answer 15

allows a determination of probability that couples will have offspring with a genetic disorder.

Question 16

oncogenes and screening

Answer 16

cancer may develop bc of mutation that prevents tumour suppressor genes inhibiting cell division.
ppl cna be screened for these mutations, both alleles need to have mutation for a tumour develop

Question 17

why would someone get screened for cancer

Answer 17

if someone is at risk they can made informed decisions about lifestyle (smoking, lose weight, eat healthy, avoid mutagens) and consider possible future treatments.
- check themselves, early signs, early diagnosis, more successful treatment

Question 18

how can genetic screening help individuals via personalised medicine?

Answer 18

• provide advice and healthcare based on individs genotype
• some genes mean specific drugs are more / less effective at treating a condition
• saves money by not overprescribing drugs that have no effect. also prevents harm from drugs