2.7 Genetic control of Metabolism in microorganisms

Question 1

How can wild strains of microorganisms with the potential to be used in industry in the production of a desired product be improved?

Answer 1

by mutagenesis, selective breeding and culture, or recombinant DNA technology (genetic engineering)

Question 2

What is mutagenesis?

Answer 2

process of inducing mutations

Question 3

how can mutagenesis be increased?

Answer 3

can be increased artificially by exposing organisms to mutagenic agents such as
- exposure to UV light, other forms of radiation or mutagenic chemicals results in random mutations, some of which might introduce an improved strain with desirable qualities

Question 4

What are improved microorganisms?

Answer 4

improved microorganisms for an industrial application could refer to their ability to be culture in a low - cost medium or to the fact the production of the desired product is increased.

Question 5

What are mutant strains?

Answer 5

often genetically unstable and revert to the wild type in continuous culture

Question 6

The transfer of DNA using bacteria?

Answer 6

some bacteria can transfer plasmids or pieces of chromosomal DNA to each other or take up DNA from their environment to produce new strains

Question 7

New strains of bacteria species can arise from horizontal transfer of DNA. What are the processes that produce new strains of microorganisms with different genotypes?

Answer 7

transformation
transduction
conjugation

Question 8

What is transformation?

Answer 8

a fragment of DNA or a plasmid from one bacterium is taken up from the environment by another bacterium

Question 9

what is conjugation?

Answer 9

a bridge forms between two different bacteria and a fragment of DNA or a plasmid is passed across

Question 10

what is transduction?

Answer 10

a virus carries genetic information from one bacterium to another

Question 11

how can new genotypes be brought about in fungi and yeast?

Answer 11

by sexual reproduction between existing strains

Question 12

Explain recombinant DNA technology?

Answer 12

RDT involves the joining together of DNA molecules from two different species
plant or animal gene sequences can be transferred to microorganisms to produce plant or animal proteins
genes that remove inhibitory control or amplify specific steps in a metabolic pathway can be introduced to increase the yield of the desired protein
as a safety mechanism, genes are often introduced that prevent the survival of a modified microorganism in an external environment

Question 13

What is selective breeding?

Answer 13

wild strains of the organisms are grown in culture under optimal conditions
pure strains for the required task can be then isolated and selected for subculture
bacteria reproduce asexually and so variation does not arise due to reproduction

Question 14

What is recombinant DNA technology?

Answer 14

RDT or genetic engineering involves the transfer of one or more genes from the genome of one organism (human) to the genome of another organism (bacteria)

Question 15

What do scientists use plasmids and artificial chromosomes as?

Answer 15

Vectors - to transfer genes coding for proteins that are useful to humans into microorganisms

Question 16

Location of desired genes?

Answer 16

uses gene probes

Question 17

What are plasmids?

Answer 17

small circular pieces of DNA 25-30 genes found in most bacterial cells and in some fungi

Question 18

What should plasmids have?

Answer 18

origin of replication
several marker genes
self replication and regulatory sequences

Question 19

What is the origin of replication?

Answer 19

refers to a specific set of genes within a plasmid that controls replication of the plasmid during cell growth and expression of the transferred gene, resulting in the generation of the required product

Question 20

What is a marker gene?

Answer 20

a gene that acts as a recognisable ‘tag’ for another closely linked gene
a specific marker gene within a recombinant plasmid can be detected, identifying which bacterial cells contain the transferred gene following cell division and growth
Marker gene can code for the production of fluorescent proteins or give the cell antibiotic resistance
The marker gene and transferred gene travel together in a plasmid

Question 21

What are artificial chromosomes?

Answer 21

artificial chromosomes are constructed in the laboratory using free DNA nucleotides and are able to carry a much larger gene into a host cell
both artificial chromosomes and plasmids acts as vectors, transporting a gene from the DNA of one species to the DNA of another species

Question 22

What is restriction endonucleases?

Answer 22

enzymes that recognise specific nucleotide sequences (restriction sites) on a DNA molecules and cut the DNA into fragments by breaking bonds at specific points along the nucleotide sequence

Question 23

How are blunt ends produced?

Answer 23

if the cut goes straight across the DNA molecule, the two strands of nucleotides will be cut at the same place producing blunt ends

Question 24

How are sticky ends produced?

Answer 24

if the nucleotides are cut at different points, several nucleotides apart, each fragment ends with a short, single stranded segment ( a sticky end)

Question 25

As each restriction enzyme will always produce fragments with the same shape of sticky ends what can be done?

Answer 25

fragments of two different DNA molecules cut with the same restriction enzyme can be joined together, forming hydrogen bonds between base pairs on the complementary sticky ends

Question 26

What is the function of DNA ligase?

Answer 26

once in position DNA ligase is used to form new bonds combining the two types of DNA more permanently

Question 27

CHECK DIAGRAM IN NOTES

Answer 27

XXXX

Question 28

TOP TIP

Answer 28

DNA restriction endonuclease acts as “scissors” cutting out a gene
DNA ligase acts as “glue” sealing the transferred gene into place

Question 29

Argument against genetic engineering?

Answer 29

microorganisms carrying a dangerous gene may escape or be stolen
GM organisms or gene sequences should not be the property of companies that develop them, but should be available to all

Question 30

Counter argument?

Answer 30

manufacturers carry out detailed risk assessments and maintain suitable standards to ensure that manufacturing processes and produces are safe
It is expensive to develop the GM organsims if parents cannot be taken out companies will not invest money to develop this technology

Question 31

Arguments in favour of technology?

Answer 31

it might improve nutrition and food security by increasing quantity and quality of food
It might improve the environment by allowing reduction of the use of pesticides or fertilisers
It might improve health by the production of drugs that are otherwise difficult to produce

Question 32

Arguments against technology?

Answer 32

the potential impact of the technology is unknown and many aspects of it such as the safety of foods or drugs remain to be understood.
the risks of the organisms or the genes they contain escaping are too great and could not be reversed
Genes are self-perpetuating and the risks they may bring about in the future are unknown

Question 33

what is a hazard?

Answer 33

a danger that could arise when carrying out a microbiological procedure

Question 34

what is a risk?

Answer 34

the likliehood of the hazard actually arising

Question 35

Why should microbiological procedures be risk assessed before they are undertaken?

Answer 35

to identify hazards and reduce risks

Question 36

TOPTIP

Answer 36

it is probably better to answer q’s about ethical issues using examples such as these rather than talking about “playing god”