DNA profiling

Question 1

what is a DNA profile

Answer 1

a visual record of some sections of DNA that can be used to identify a person

Question 2

process of DNA profiling

Answer 2

1. extract the DNA from cells with a nucleus
2. protease enzymes are used to remove histone proteins
3. specific restriction energy are added to cut the DNA into fragments
4. separate the fragments by mass using gel electrophoresis to create a banding pattern

Question 3

how is DNA amplified using a PCR machine

Answer 3

1. a reaction tube containing DNA, DNA primers, DNA polymerase, free nucleotides and buffer is heated to 95 degrees - causing hydrogen bonds between DNA strands to break
2. the reaction tube is then cooled to 55 degrees - DNA primers will attach to the nucleotides to prevent them from rejoining
3. the reaction tube is then heated to 70 degrees - the optimum temperature for DNA polymerase

Question 4

what is the role of DNA primers

Answer 4

these are short, single strands of DNA and complementary to the template strand and so bind to it to prevent the other DNA template strands from joining back together

Question 5

what is the role of free DNA nucleotides

Answer 5

they bind to the template strand by base pairing

Question 6

what is the role of DNA polymerase

Answer 6

builds the missing DNA strand by base pairing

Question 7

how can DNA profile help to identify individuals

Answer 7

1. study the patterns of bands produced like their position or width
2. bands will be in certain positions due to their mass
3. if two profiles have very similar banding patterns suggest they are closely related
4. for example if two species have similar banding patterns they will have more recent common ancestors

Question 8

why is DNA profiling not infallible

Answer 8

• a complete DNA profile would definitely be unique, but the DNA is only sampled
• as only a few repeated sequences are analysed, it is less likely to be completely unique especially if people are closely related