DNA profiling

Question 1

What is the genome of an organism?

Answer 1

• all the genetic material it contains
• DNA and mitochondrial DNA combines

Question 2

What are exons and introns?

Answer 2

• inons are non-conding regions of DNA
  
  • removed from mRNA before it is translated into polypetide chains knwon as introns
• most of the DNA is inons

Question 3

What is DNA profilings?

Answer 3

• producing an image of the patterns in the DNA of an individual

Question 4

What is a satellite?

Answer 4

• a sequence of base pairs that are repeated many time
• appear in same positions on chromomes, but microsatellites varies between individuals, as different lengths of repeats
• satellite patterns can be compared

Question 5

What is the first stage of DNA profiling?

Answer 5

• DNA must be extracted from tissue sample

Question 6

How much DNA is needed?

Answer 6

• used to need the equivalent to the DNA from the nuceli of 10,000 humans cells
• now using the polymerase chain reaction, tinisest fragment can be used to develop a profile

Question 7

How is the sample digested?

Answer 7

• DNA cut into small fragments using enzymes called restriciton endonucleases
• make 2 cuts, once through each strand of the DNA double helix

Question 8

What are the function of different restriction endonucleases?

Answer 8

• Different restriction endonucleases cut DNA at a specific nucleotide sequence, knwon as the restriction or recognition site
• allow scientists to cut DNA at defined points in the introns
  
  • leaves satellite regions unharmed as cut at

Question 9

How are the DNA fragments separated?

Answer 9

• must be separated to form a clear, recognisable pattern
• done using electrphoresis
  
  • utilises the way charged particles move throiugh a gel medium under the influence of an electric current
• the gel is then immersed in alkali to separate the DNA double strands into single strands
• fragmetns are then transferred onto a membrane by Southern blotting

Question 10

What is hybridisation?

Answer 10

• radioactive or fluorescent DNA probes are now added in excess to the DNA fragments on the mebrane
• DNA probes are short DNA or RNA sequences complementary to a known DNA sequence
• they bind to the complementary strands of DNA under particular conditions of pH and temperature
• this is hybridisations
• • excess probesa are washed

Question 11

What is the function of the probes?

Answer 11

DNA probes identify the microsatellite regions that are more varied than the larger minisatellite regions

Question 12

How can the evidence be observed?

Answer 12

• if radioactive labels added to DNA probes, x-ray images are taken of the paper/membrane
• if fluorescent labels were added to the DNA probes, the paper/membrane is placed under UV light so the fluorescent tags glow