Higher Biology Unit 2 2.7 Genetic Control of Metabolism - PowerPoint Presentation

Slide1

Higher Biology

Unit 2

2.7 Genetic Control of Metabolism

Slide2

Wild Type Microbes

W

ild type

is the typical

form

of a species found in

nature

.

A wild type microbe can be selected for use in industry due to it exhibiting a

desirable genetic trait

.

Even with this desirable trait, it may lack other important traits.

S

cientists try to

improve

the microbe to include the genetic material for these other traits.

Slide3

Wild Type Microbes

Examples of traits hoped to be gained by

strain improvement

include;

the ability

to grow on low cost growth

medium

g

enetic stability

production of large quantities of secondary

metabolites

Slide4

Wild Type Microbes

Wild types of microbes are improved for use in biotechnology by

altering the microbe’s

genome.

This can be done in different ways;

Mutagenesis

Selective Breeding

Recombinant DNA

Slide5

Mutagenesis

Mutagenesis is the creation

of

mutations

.

In nature, mutations;

a

re rare

o

ccur spontaneously and at randomare usually detrimental to the organism

Slide6

Mutagenesis

The

rate of

mutation can

be increased by the use of

mutagenic

agents

.

Examples include;

radiation e.g. UV light and

X rays

c

hemicals such as mustard gas

Slide7

Mutagenesis

On

very rare occasions,

a

mutant

allele can arise

that confers an advantage

to the

organism or endows it with a new property that

is useful to humans.

Therefore, mutagenesis can be useful during industrial processes as a microbe may develop a new property that proves useful to humans.

Slide8

Mutagenesis

Unfortunately, mutated

strains of

microbes tend to be

genetically unstable

.

This means

they

sometimes undergo a reverse mutation

, reverting to

the

original (and less useful) wild type.This would be very costly in terms of time and

resources

.

In industry, an improved

strain of

microbe must be

monitored regularly to ensure that

it is

still in its mutated

form before

it is

used.

Slide9

Selective Breeding

Sexual

Reproduction

Two parents

Fusion of

male & female

gametes,

forming a

zygote

Offspring show variation

Some eukaryotic cells e.g. yeasts

Asexual

Reproduction

One parent

No gametes involved

Offspring are clones

Some eukaryotic cells e.g. yeasts

Bacteria

Slide10

Selective Breeding

By

deliberately crossing different strains

during breeding

programmes, scientists are able to

produce new strains of microbes.

On

some

occasions,

a new strain combines two desirable characteristics, one from each parent.

Slide11

Selective Breeding

Slide12

Selective Breeding

Horizontal Transfer

Although bacteria

don’t

reproduce sexually, new strains can arise as a result of

horizontal transfer

of genetic material.

During this, plasmids

or pieces of

DNA can be

transferred from one strain to

another via a

conjugation tube.

Slide13

Selective Breeding

Horizontal Transfer

New strains are also produced by bacteria taking up

DNA

fragments from their environment.

Scientists try to

produce new strains of useful bacteria by culturing

existing strains

together in conditions where horizontal transfer of DNA is most likely to

occur.

Slide14

Recombinant DNA

This is the transfer of genes

from

one organism

to

another (can be of different species).

Think:

genetic engineering

from National 5

.This allows bacteria to produce plant

or animal proteins e.g. human insulin.

The bacterium is

said to be artificially transformed

.

Slide15

Enzymes

In recombinant DNA, two different types of enzyme are used

;

restriction endonucleases

ligase

Slide16

Restriction Endonucleases

These enzymes are taken from microbes

They are used

to cut DNA

from both the donor and the receiving plasmid

They recognise

specific sequences

of DNA bases

called restriction sites

Slide17

Restriction Endonucleases

The

same

restriction endonuclease

must be used to cut both donor and plasmid

This ensures the

ends of

both

DNA fragments have DNA bases that are complementary

to each other

The ends of the cut DNA fragments are

described as “sticky”

Slide18

Restriction Endonucleases

The

sticky ends

of the required gene and plasmid

stick

together because their DNA bases are

complimentary

Slide19

Ligase

These enzymes stick the DNA fragments together.

This seals the desired gene into the plasmid

Each end of the fragments must have complementary bases

Slide20

Vectors

In recombinant DNA, the gene is transferred

by a

vector

.

The vector is usually a

plasmid

or an

artificial chromosome.

Artificial chromosomes can transfer much longer DNA sequences

Slide21

Vectors

To be an effective vector, a plasmid must have three

features;

r

estriction site

marker gene

o

rigin of replication

Restriction

site

Marker

gene

Origin

of

replication

Slide22

Restriction site

M

ust

be able to be

opened

with the

same

restriction endonuclease

used

to cut open the donor DNAThis ensures that the sticky ends of both donor DNA and the plasmid DNA are

complementary

Slide23

Marker gene

This gene

shows if the cell

has

taken

up the

plasmid.

It is usually a gene that gives the bacterium resistance

to an antibiotic

.A

ny cell

that

hasn’t taken up the plasmid will die as it has no resistance to the antibiotic

Slide24

Origin of replication

This consists of genes that control

self replication

of the

plasmid

It is needed to make many

copies of the plasmid

(carrying

the desired gene) within the

bacterial cell

.

Slide25

Recombinant DNA

Improvements made to microbes include;

Amplifying specific

steps in a metabolic

pathway or removing

inhibitors to

increase the yield of desired product

.

The ability to secrete product into the

surrounding medium. This allows

it to be collected

easily,

saving resources.Ensuring it can’t

survive in

the

external environment. This is a

safety precaution

.

Slide26

Recombinant Y

east Cells

Sometimes there are problems with bacterial cells producing the desired protein e.g.

They don't secrete the

protein into the

surrounding medium

T

hey degrade the protein before it can be collected

Slide27

Recombinant Y

east Cells

In these cases,

genetically transformed eukaryotic cells

e.g. yeast is a preferable option.

This is despite eukaryotic cells having more demanding cultural conditions.