DNA profiling

Question 1

why are STRs used?

Answer 1

highly polymorphic (many versions exist)

no selective pressure

inherited by parents

Many loci can be analysed

low probability of a random match

Question 2

What type of DNA is used in DNA profiling

Answer 2

non-coding DNA containing STR

Question 3

What are STRs?

Answer 3

Short Tandem Repeats — short base sequences repeated multiple times.

Question 4

Why does DNA move in gel electrophoresis?

Answer 4

DNA is negatively charged and moves towards the positive electrode

Question 5

How can a DNA profile be produced from a small sample of DNA?

Answer 5

DNA is amplified using PCR

In PCR, DNA is denatured and primers anneal to complementary sequences

Amplified DNA fragments are separated by gel electrophoresis with smaller fragments moving through the gel toward the positive electrode

Question 6

What does PCR stand for

Answer 6

polymerase chain reaction

Question 7

How can 2 DNA profiles be compaired

Answer 7

compairing total number of bands

comparing the position of the bands

and comparing the size and width of the bands

Question 8

The DNA produced by PCR was analysed to find out if a black panther was involved.

Explain how gel electrophoresis could be used to find out if this DNA came from a black panther.

Answer 8

use a buffer solution to load electrophoresis tank

apply a current to the gel

get DNA from the black panther

use gene probe to denature DNA

compair bands a match in bands would indicate DNA from black panther is present

Question 9

State two features of these bodies can effect body cooling

Answer 9

size of body

possition of body during death

fat level

Question 10

Explain why recording rectal temperature is more reliable than measuring skin temperature

Answer 10

there is more variation in skin temperature around the body

rectal temperature would be 37oc at the time of death

Question 11

The quantity of worm DNA in the beetle gut was very small.

Describe how sufficient DNA was produced to carry out the analysis.

Answer 11

DNA is amplified using the PCR

PCR uses primers which have a specific base sequence

primers anneal to single-stranded DNA at 50C

DNA is denatured at 95C

Question 12

What are the temperature requirements to denature and anneal

Answer 12

denature is done at 95c

Annealing is done at 50c

Question 13

In gel electrophoresis, which direction do DNA fragments move and why?

Answer 13

DNA fragments are negatively charged, so they move towards the anode (positive electrode). Smaller

Question 14

Explain the role of DNA primers in the production of the amplified 345bp sequence

Answer 14

Primers have a specific base sequence

anneal to complementary bases of DNA be amplified

Therefore, provide a site for DNA polymerase to bind