2.7 genetic control of metabolism

Question 1

How can wild strains of microorganisms be improved?

Answer 1

• mutagenesis

- recombinant DNA technology

Question 2

Explain how mutagenesis works

Answer 2

• exposure to UV light and other forms of radiation or mutagenic chemicals result in random mutations
• some of which may produce an improved stain of microorganism with desirable qualities

Question 3

What is recombinant DNA technology?

Answer 3

the use of recombinant plasmids and artificial chromosomes as vectors

Question 4

What is a vector?

Answer 4

• a DNA molecules used to carry foreign genetic information into another cell
• both plasmids and artificial chromosomes are used as vectors

Question 5

When are artificial chromosomes preferred to plasmids as vectors?

Answer 5

when larger fragments of foreign DNA are require to be inserted

Question 6

What is the role of the enzyme restriction endonuclease?

Answer 6

-cut open plasmids and cut specific genes out of chromosomes, leaving sticky ends

Question 7

when are complementary sticky ends produced?

Answer 7

-when the same restriction endonuclease is used to cut open the plasmid and cut the gene from the chromosome.

Question 8

What is the role of Ligase in in recombinant DNA technology?

Answer 8

ligase seals the gene into the plasmid

• to seal complimentary DNA fragments into place
• complementary DNA fragments are required to insert them into a plasmid or chromosome

Question 9

What are the five different sections to recombinant plasmids and artificial chromosomes?

Answer 9

• restriction sites
• regulatory sequences
• origin of replication
• selectable marker gene
• safety gene

Question 10

What is a restriction site?

Answer 10

• contain target sequences of DNA where
• specific restriction endonuclease cut (the same one used to extract the gene from the chromosome)
• leaving sticky ends

Question 11

What is a regulatory sequence?

Answer 11

DNA sequence which controls gene expression

Question 12

What is the origin of replication?

Answer 12

allows self-replication of the plasmid/artificial chromosome

Question 13

What are selectable marker genes?

Answer 13

• protect the microorganism from a selective agent that would normally kill it or prevent it growing
• ensures that only the micro-organisms which have taken up the vector grow in the presence of the selective agent

Question 14

What safety mechanism is often used in recombinant DNA technology?

Answer 14

genes are introduced that prevent the survival of the microorganism in an external environment

Question 15

Why are recombinant yeast cells used in recombinant DNA technology?

Answer 15

• plant or animal recombinant DNA expressed in bacteria may result in polypeptides being incorrectly folded
• recombinant yeast cells produce active forms of the protein which are inactive in bacteria

Question 16

What is mutagenesis?

Answer 16

the process of inducing mutations

Question 17

What could improved microorganisms refer to when being used in an industry setting?

Answer 17

• cultured in a low cost medium

- production of required product is increased

Question 18

How can microorganisms be transformed?

Answer 18

by transferring plant or animal gene sequences to them

Question 19

What is the definition of recombinant DNA technology?

Answer 19

the joining together of DNA molecules from two different species

Question 20

What gene sequences can be transferred to microorganisms? and to produce what?

Answer 20

• plant or animal gene sequences

- produce plant or animal proteins

Question 21

describe the process of genetic engineering?

Answer 21

-DNA is extracted and then the required gene is cut out using restriction endonuclease

• isolation of bacterial plasmid
• plasmid extracted and cut open using the same restriction endonuclease
• DNA ligase seals required gene into plasmid
• recombinant plasmid taken up by host cell
• host cell then replicates itself

Question 22

What can plant or animal recombinant DNA expressed in bacteria result in?

Answer 22

the production of polypeptides that are folded incorrectly and are non-functional