Gene Technology

Question 1

How do restriction endonucleases cut DNA into smaller fragments

Answer 1

Enzymes which cut DNA at specific base sequences along the sugar-phosphate backbone, producing either blunt or sticky ends

Question 2

How is DNA made from RNA

Answer 2

1. Isolate and extract mRNA from the desired gene
2. Reverse Transcriptase is used to make a single strand of DNA using mRNA as a template
3. DNA polymerase used to make double stranded DNA from single strand
4. Required gene produced

Question 3

How is a DNA probe used

Answer 3

-Used to locate a particular nucleotide sequence or gene on DNA molecule
-short section of DNA- contain known base sequence
labelled either
-radioactive
-fluorescent
-Bases in DNA probe hybridise with complementary bases on donor DNA- reveal position on gene

Question 4

Once the gene is located, how is it extracted?

Answer 4

1. The target DNA is hydrolysed by restriction endonucleases and the DNA fragments are separated by gel electrophoresis.
2. The target DNA is transferred onto a nylon membrane and a fluorescent DNA probe is added.
   -any DNA which is not attached will be washed off, as it would still show up.
3. When exposed to light, the DNA probe and target sequence would show as a fluorescent band.
4. Gel electrophoresis separates DNA fragments based on size, will smaller fragments travelling further and faster through the gel