Genetics

Question 1

What is the genome?

Answer 1

Total of all genetic material in organism

Consists of exons, which are coding regions

Consists of introns, which are non coding regions

Question 2

How does PCR work

Answer 2

It amplifies DNA to produce a bigger sample

Step 1: Heat to 95 degrees to separate DNA

Step 2: Cool to 55 degrees to allow primers to bind

Step 3: Heat at 72 degrees to allow Taq DNA polymerase to function

Repeat 30 times

Required equipment is primers, thermocycler and small sample of DNA

Question 3

Outline DNA sequencing

Answer 3

DNA strands are chopped into smaller pieces

Double strands separated into single strands

PCR to amplify DNA

Labelled terminator bases are added. When a terminator base is incorporated the chain is halted

Coloured tags allow sequence of bases to be read rapidly by automated system

Question 4

What is DNA profiling

Answer 4

Identification of repeating patterns in the non-coding regions of DNA

Question 5

About introns and satellites

Answer 5

Over 90% of DNA is non-coding (introns)

These introns can code for siRNA (small interfering) that interact with mRNA and prevent certain proteins being made

Micro-satellite is a section of DNA with a 2-6 base sequence repeated between 5 and 100 times

Mini-satellite is a section of DNA with a 10-100 base sequence repeated 50 to several hundred times

Question 6

How is gel electrophoresis carried out

Answer 6

DNA cut into fragments using restriction enzymes

Cut at specific recognition sites and placed in wells

Agarose gel medium in buffering solution. Gel contains dye that binds to DNA fragments

Visible dye added, which travels through gel faster than DNA to turn off current

Electric current passed. DNA fragments move to positive anode due to phosphate group in DNA backbone

Move at different rates according to size and charge.Plate then placed under UV light so DNA fluoresces

Question 7

Describe southern blotting

Answer 7

Alkaline buffer solution is added to gel after electrophoresis

Nylon filter added. This draws up DNA fragment solution.
DNA fragments are attached as blots

Alkaline solution denatures the DNA fragments so they separate and base sequence is exposed

Question 8

Describe hybridisation

Answer 8

Gene probes added to filter. Short DNA strands with fluorescent label complementary to specific DNA sequence sought

The binding of gene probes to complementary DNA strands is hybridisation

DNA profile is produced as a graph.