History or DNA profiling

Question 1

give 6 properties of a good genetic marker

Answer 1

highly polymorphic

cheap and easy to characterise

profiles simple to interpret and compare

low mutation rate

ability to automate

deal well with mixed samples

Question 2

what was the first genetic tool for distinguishing between individuals

Answer 2

blood groups

Question 3

problems with blood groups

Answer 3

not very informative - poor power of discrimination

need large sample

Question 4

what is an antibody

Answer 4

protein produced by immune system to recognise and neutralise pathogens

Question 5

what is an anitgen

Answer 5

target for antibodies. foreign substance that provokes immune response

Question 6

what other system is similar to blood grouping

Answer 6

rhesus system

50 antigens but D most commonly referred too

RhD+ or RhD-

even when combines with ABO, only 8 possible combinations

Question 7

protein markers

Answer 7

polymorphic protein systems were utilised in forensics

technique called isoelectric focusing

Question 8

what are restriction enzymes

Answer 8

enzymes from bacteria

cut DNA at specific location known as restriction site

essential tools for genetic manipulation

restriction sites are usually DNA sequences of 4-6 nucleotides that the enzyme scans the genome for

Question 9

what is gel electrophoresis

Answer 9

separation of DNA fragments cut by restriction enzymes

see notes for step by step

Question 10

what is southern blotting

Answer 10

DNA fragment detection

see notes for step by step

Question 11

what are RFLPs

Answer 11

restriction fragment length polymorphisms

Question 12

RFLPs

Answer 12

determines by presence/absence of restriction sites

substitution of a single base in the DNA sequence can either create or destroy a restriction site

creation of new restriction site will create 2 smaller fragments where before there was 11 larger fragment

destruction of a restriction site would have the opposite effect

only 2 alleles at a specific locus - have restriction site or not

not very discriminatory for forensic purposes

are inherited in a Mendelian fashion

Question 13

what are VNTRs

Answer 13

variable number tandem repeats

type of RFLP

also called mini satellites

regions of the DNA that contain DNA sequences that are repeated

number of repeats varies fro person to person

Question 14

what are multi locus probes

Answer 14

probes that recognise sequences belonging to length polymorphisms at a number of genetic loci simultaneously

produces a complex pattern of bands called a ‘DNA fingerprint’

Question 15

what are single locus probes

Answer 15

probes that are specific for only one mini satellite

need smaller amount of DNA

generate simpler results

increase power of discrimination by combining various SLPs

Question 16

what are the limitations of RFLPs

Answer 16

time consuming

lot of expertise needed to produce results and interpret

large amount of starting material needed

good quality DNA needed

Question 17

what are STRs

Answer 17

short tandem repeats

also called micro-satellites

variable, repeated DNA

analysis based on PCR