producing DNA fragments

Question 1

Recombination DNA technology involves

Answer 1

the transfer of fragments of DNA from one organism, or species, to another

Question 2

what feature of the genetic code means the transferred DNA can be translated within cells of the recipient
(transgenic) organism?

Answer 2

the genetic

code is universal, as are transcription and translation mechanisms

Question 3

Fragments of DNA can be produced by several methods, including:

Answer 3

• conversion of mRNA to complementary DNA (cDNA), using reverse transcriptase
• using restriction enzymes (endonucleases) to cut a fragment containing the desired
gene from DNA
• creating the gene in a ‘gene machine’

Question 4

explain how fragments of DNA can be produced using reverse transcriptase?

Answer 4

• beta cells in the islets of Langerhan in the human pancreas are specialised to produce insulin, so they make alot of mRNA that codes for insulin and easily extracted
• the mRNA acts as a template on which a single-stranded complementary of DNA (cDNA) is formed using reverse transcriptase
• single-stranded cDNA is isolated by hydrolysis of the mRNA with an enzyme
• double-stranded DNA is formed on the template of cDNA using DNA polymerase
• creating a copy of the human insulin gene

Question 5

what is the role of restriction endonucleases?

Answer 5

bacteria are frequently infected by viruses that inject their DNA into them in order to take over the cell= some bacteria protect themselves by producing enzymes that cut up the viral DNA- restriction endonucleases

Question 6

there are many times of restriction endonucleases and each one cuts a DNA strand at a specific sequence of bases called a recognition sequence- where can this occur?

Answer 6

1- sometimes this cut occurs between two opposite base pairs leaving 2 straight edges known as ‘blunt ends’
2- others cut DNA in a staggered fashion often at six bp palindromic sequences leaving ‘sticky ends’ in which each strand of DNA has exposed, unpaired bases

Question 7

are blunt or sticky ends of most importance in gene tech?

Answer 7

sticky ends

Question 8

explain how a gene is manufactured in the ‘gene machine’?

Answer 8

1- determine the amino acid sequence of the protein
2- look up the mRNA codons
3- work out the complementary DNA triplets
4- enter the DNA code into a computer
5- in an automated process, the nucleotides are assembled in the correct order to make a gene
6- the gene is replicated using PCR
7- the gene can then be inserted into a plasmid where it can be transferred into another organism in the future