7.1 3 DNA profiling

Question 1

DNA profiling

Answer 1

the identification of repeating patterns in the non-coding regions of DNA
Allows us to identify individuals,species ,forensic science and paternity testing

Question 2

introns

Answer 2

reptitive coding regions between genes

are inherited in the same way as active genes

Question 3

function of introns

Answer 3

can code for small interfering RNA molecules siRNA that interact with mRNA to prevent the production of certain proteins

Question 4

within the introns

Answer 4

there are short sequences of DNA that are repeated many times to from micro-satelltes and mini-satellites
same mini or micro appear same position on homologous pairs of chromosomes
what varies is the number of repeates on the maternal and paternal chromosomes

Question 5

mini-satellite

Answer 5

10-100 bases repeate 50 to several hundred times

Question 6

micro-satellite

Answer 6

2-6 bases repeated 5 to 100 times

Question 7

the more closely related two individuals

Answer 7

the more likely there will be similarties in their DNA patterns

Question 8

FIRST STAGE of DNA profiling

Answer 8

PCR?
strands of DNA from a sample are cut using restriction endonucleases
these enzymes cut the DNA at particular points in intron sequences

Question 9

recognition sites

Answer 9

different restriction enzymes cut a DNA molecules into fragements at different specific base sequences which are the recogniton sites

Question 10

using a restriction enzyme

Answer 10

that cut either side of a micro or milli satellite unit leaves the repeated sequences intact giving a mixture of different sized DNA fragments depending on the number of repeated sequences

Question 11

SECOND STAGE

Answer 11

Gel electrophoresis

fragments need to be separated and identified

Question 12

process of gel electrophoresis

Answer 12

DNA fragments are placed in wells in agarose gel medium in a buffering solution with a known DNA frament to aid identification
gel contains a dye such as ethidium bromide whcih binds to the DNA fragments in the gel
the dye will fluoresce when placed under UV revealing band of DNA

Question 13

A visable dye

Answer 13

Also added to DNA samples doesnt bind but moves through gel slightly faster than DNA so current can be turned off before samples run off the end

Question 14

An electric current

Answer 14

passed through the apparatus and the DNA fragments move towards the positive anode because of the negative charge of the phosphate groups in the DNA backbone

Question 15

Fragements

Answer 15

Move at different rates according to size due to how easily move through pores in the agrose jelly

Question 16

THIRD STAGE

Answer 16

Souther blotting
Alkaline buffer solution is added to gel after electrophoresis and a nylon filter or nyloncellulose paper is placed over it
dry absorbent material used to draw solution containing DNA from gel to filter leaving DNA as blots attached to the filter

Question 17

alkaline solution

Answer 17

also denatures the DNA fragments so the strands separate and the base sequences are exposed
DNA then covalently bound by UV cross linking

Question 18

After southern blotting process

Answer 18

large quantities of single stranded gene probes are added to the filter and bind to complementary DNA strands in a process known as hybridisation

Question 19

gene probes

Answer 19

short DNA sequences complementary to specific sequences being sought each probe is labelled to a fluorescent molecule or radioactive isotope
excess probes are washed away and filter placed under a UV light to show up DNA regions

Question 20

result

Answer 20

A DNA profile is produced as a graph with each peak representing the number of microsatellite repeats in a fragment

Question 21

forensic science

Answer 21

gene probes are used to pick out short tandem repeats which are micro-satellite regions largely used in DNA identification

Question 22

paternity testing

Answer 22

Specific micro-satellite markers are used to make the matches
microsatllies must come from mother or father cant be traced to mother or alleged father then isnt the father