21.5 genetic fingerprinting

Question 1

what are VNTRs?

Answer 1

variable number tandem repeats (non-coding dna bases)

Question 2

why are VNTRs used in genetic fingerprinting?

Answer 2

number and length of VNTRs are different between individuals & give a unique pattern
- closer relatives would have similar VNTRs pattern

Question 3

what are the 5 steps of genetic fingerprinting?

Answer 3

1) extraction
2) digestion
3) separation
4) hybridisation
5) development

Question 4

how is dna extracted and amplified in genetic fingerprinting?

Answer 4

dna is extracted from tissue of interest (eg. swab, syringe) & amplified by PCR

Question 5

what is used in digestion of genetic fingerprinting & how is it carried out?

Answer 5

restriction endonuclease cut dna into fragments
- recognition sites (in palindromes) will be different due to different VNTRs -> different dna fragments are made

Question 6

how is gel electrophoresis carried out? (3)

Answer 6

• dna placed in well of gel & is attracted to positive voltage (since phosphate groups of dna is negative)
• gel offers resistance to dna fragments & smaller fragments travel furthest
• radioactively labelled dna is used to bind to VNTRs & gel is exposed to x-ray film

Question 7

how is separation of dna carried out after gel electrophoresis?

Answer 7

gel is immersed in alkaline solution to change double-stranded DNA -> single stranded DNA fragments
- single stranded DNA is transferred from gel to nylon membrane by southern blotting

Question 8

how is hybridisation carried out in dna separation?

Answer 8

radioactively dna probes are added to single-stranded dna fragments on nylon membrane
- probes are complementary to VNTRs and bind under specific conditions of temperature & pH

Question 9

how are hybridised dna fragments developed?

Answer 9

x-ray film is put over nylon membrane & radiation exposes the film and shows dark lines
- unique dna pattern for each individual
- results are interpreted & developed -> probability of dna being from same individual is calculated

Question 10

what are the 4 uses of dna fingerprinting?

Answer 10

1) determine genetic variation & relationships
2) forensic science (crime scenes)
3) medical diagnosis
4) plant & animal breeding

Question 11

how is dna fingerprinting used in diagnosing huntington’s disease?

Answer 11

determine number of AGC base sequence repeated:
<30 unlikely
>38 almost certain
>50 early onset

Question 12

how is dna fingerprinting used in plant & animal breeding? (3)

Answer 12

prevent undesirable breeding on farms & zoos
determine paternity for pedigree
identify organism with certain beneficial allele of a gene for breeding purposes