Genetic engineering and biotechnology - LancyBiologyIB

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Dec 12, 2012 (4 years and 4 months ago)

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Genetic engineering and biotechnology



4.4.1

Outline

the

use

of

polymerase

chain

reaction

(PCR)

to

copy

and

amplify

minute

quantities

of

DNA.

Polymerase

chain

reaction

is

used

to

copy

and

amplify

minute

quantities

of

DNA.

It

can

be

useful

when

only

a

small

amount

of

DNA

is

available

but

a

large

amount

is

required

to

undergo

testing.

We

can

use

DNA

from

blood,

semen,

tissues

and

so

on

from

crime

scenes

for

example.

The

PCR

requires

high

temperature

and

a

DNA

polymerase

enzyme

from

Thermus

aquaticus

(a

bacterium

that

lives

in

hot

springs).



4.4.2

State

that,

in

gel

electrophoresis,

fragments

of

DNA

move

in

an

electric

field

and

are

separated

accor
ding

to

their

size.

In

gel

electrophoresis,

fragments

of

DNA

move

in

an

electrical

field

and

are

separated

according

to

their

size.




4.4.3

State

that

gel

electrophoresis

of

DNA

is

used

in

DNA

profiling.

Gel

electrophoresis

of

DNA

is

used

in

DNA

profiling.



4.4.4

Describe

the

application

of

DNA

profiling

to

determine

paternity

and

also

in

forensic

investigations.

Organisms

have

short

sequences

of

bases

which

are

repeated

many

times.

These

are

called

satellite

DNA.

These

repeated

sequences

vary

in

length

from

person

to

person.

The

DNA

is

copied

using

PCRand

then

cut

up

into

small

fragments

using

restriction

enzymes.

Gel

electrophoresis

separates

fragmented

pieces

of

DNA

according

to

their

size

and

charge.

This

gives

a

pattern

of

bands

on

a

gel

whic
h

is

unlikely

to

be

the

same

for

two

individuals.

This

is

called

DNA

profiling.

DNA

profiling

can

be

used

to

determine

paternity

and

also

in

forensic

investigations

to

get

evidence

to

be

used

in

a

court

case

for

example.


4.4.5

Analyse

DNA

profiles

to

draw

conclusions

about

paternity

or

forensic

investigations.

For

a

suspect

look

for

similarities

between

the

DNA

found

at

the

crime

scene

and

the

suspect.

For

a

paternity

test,

look

for

similarities

between

the

child

and

the

possible

father.



4.4.6

Outline

th
ree

outcomes

of

the

sequencing

of

the

complete

human

genome.



It

is

now

easier

to

study

how

genes

influence

human

development.




It

helps

identify

genetic

diseases.



It

allows

the

production

of

new

drugs

based

on

DNA

base

sequences

of

genes

or

the

structure

of

proteins

coded

for

by

these

genes.



It

will

give

us

more

information

on

the

origins,

evolution

and

migration

of

humans.



4.4.7

State

that,

when

genes

are

transferred

between

species,

the

amino

acid

sequence

of

polypeptides

translated

from

them

is

unchan
ged

because

the

genetic

code

is

universal.

When

genes

are

transferred

between

species,

the

amino

acid

sequence

of

polypeptides

translated

from

them

is

unchanged

because

the

genetic

code

is

universal.



4.4.8

Outline

a

basic

technique

used

for

gene

transfer

involving

plasmids,

a

host

cell

(bacterium,

yeast

or

other

cell),

restriction

enzymes

(endonucleases)

and

DNA

ligase.

The

human

gene

that

codes

for

insulin

can

be

inserted

into

a

plasmid

and

then

this

plasmid

can

be

inserted

into

a

host

cell

such

as

a

bac
terium.

The

bacterium

can

then

synthesis

insulin

which

can

be

collected

and

used

by

diabetics.

This

is

done

as

follows.

The

messenger

RNA

which

codes

for

insulin

is

extracted

from

a

human

pancreatic

cell

which

produces

insulin.

DNA

copies

are

then

made

fro
m

this

messenger

RNA

by

using

the

enzyme

reverse

transcriptase

and

these

DNA

copies

are

then

given

extra

guanine

nucleotides

to

the

end

of

the

gene

to

create

sticky

ends.

At

the

same

time,

a

selected

plasmid

is

cut

using

restriction

enzymes

which

cut

the

D
NA

at

specific

base

sequences.

Then

extra

cytosine

nucleotides

are

added

to

create

sticky

ends.

Once

we

have

both

the

plasmid

and

the

gene

ready,

these

are

mixed

together.

The

two

will

link

by

complementary

base

pairing

(between

cytosine

and

guanine)

and

t
hen

DNA

ligase

is

used

to

make

the

sugar

phosphate

bonds.

The

plasmids

with

the

human

insulin

gene

(called

recombinant

plasmids)

can

then

be

mixed

with

host

cells

such

as

bacterium.

The

bacterium

will

take

in

the

plasmid

and

start

producing

insulin

which

c
an

then

be

collected

and

purified.



4.4.9

State

two

examples

of

the

current

uses

of

genetically

modified

crops

or

animals.



The

transfer

of

a

gene

for

factor

IX

which

is

a

blood

clotting

factor,

from

humans

to

sheep

so

that

this

factor

is

produced

in

the

sheep’s

milk.



The

transfer

of

a

gene

that

gives

resistance

to

the

herbicide

glyphosate

from

bacterium

to

crops

so

that

the

crop

plants

can

be

sprayed

with

the

herbicide

and

not

be

affected

by

it.




4.4.10

Discuss

the

potential

benefits

and

possible

harmfu
l

effects

of

one

example

of

genetic

modification.

It

is

quite

common

to

see

genetic

modifications

in

crop

plants.

An

example

of

this

is

the

transfer

of

a

gene

that

codes

for

a

protein

called

Bt

toxin

from

the

bacterium

Bacillus

thuringiensis

to

maize

crops.

This

is

done

because

maize

crops

are

often

destroyed

by

insects

that

eat

the

corn

and

so

by

adding

the

Bt

toxin

gene

this

is

prevented

as

the

toxin

kills

the

insects.

However

this

is

very

controversial

as

even

though

it

has

many

positive

ad
vantages,

it

can

also

have

some

harmful

consequences.

The

table

below

summarizes

the

benefits

and

possible

harmful

effects

of

genetically

modifying

the

maize

crops.






Benefits

Harmful

Effects

Since

there

is

less

damage

to

the

maize

crops,

there

is

a

higher

crop

yield

which

can

lessen

food

shortages.

We

are

not

sure

of

the

consequences

of

humans

and

animals

eating

the

modified

crops.

The

bacterial

DNA

or

the

Bt

toxin

itself

could

be

harmful

to

human

as

well

as

animal

health.

Since

there

is

a

higher

crop

yield,

less

land

is

needed

to

grow

more

crops.

Instead

the

land

can

become

an

area

for

wild

life

conservation.

Other

insects

which

are

not

harmful

to

the

crops

could

be

killed.

The

maize

pollen

will

contain

the

toxin

and

so

if

it

is

blown

onto

near

by

plants

it

can

kill

the

insects

feeding

on

these

plants.


There

is

a

reduction

in

the

use

of

pesticides

which

are

expensive

and

may

be

harmful

to

the

environment,

wild

life

and

farm

workers.


Cross

pollination

can

occur

which

results

in

some

wild

plants

b
eing

genetically

modified

as

they

will

contain

the

Bt

gene.

These

plants

will

have

an

advantage

over

others

as

they

will

be

resistant

to

certain

insects

and

so

some

plants

may

become

endangered.

This

will

have

significant

consequences

on

the

population

of

wild

plants.




4.4.11Define

clone.

Clone:

a

group

of

genetically

identical

organisms

or

a

group

of

genetically

identical

cells

derived

from

a

single

parent

cell.


4.4.12

Outline

a

technique

for

cloning

using

differentiated

animal

cells.

Dolly

the

sheep

was

cloned

by

taking

udder

cells

from

a

donor

sheep.

These

cells

were

than

cultured

in

a

low

nutrient

medium

to

make

the

genes

switch

off

and

become

dormant.

Then

an

unfertilized

egg

was

taken

from

another

sheep.

The

nucleus

of

this

egg

cel
l

was

removed

by

using

a

micropipette

and

then

the

egg

cells

were

fused

with

the

udder

cells

using

a

pulse

of

electricity.

The

fused

cells

developed

like

normal

zygotes

and

became

embryos.

These

embryos

were

then

implanted

into

another

sheep

who’s

role

was

to

be

the

surrogate

mother.

One

lamb

was

born

successfully

and

called

Dolly.

Dolly

was

genetically

identical

to

the

sheep

from

which

the

udder

cells

were

taken.

4.4.13

Discuss

the

ethical

issues

of

therapeutic

cloning

in

humans.

There

are

many

ethical

iss
ues

involving

therapeutic

cloning

in

humans.

Below

is

a

table

summarizing

the

arguments

for

and

against

therapeutic

cloning

in

humans.






Arguments

for


Arguments

against

Embryonic

stem

cells

can

be

used

for

therapies

that

save

lives

and

reduce

pain

for

patients.

Since

a

stem

cell

can

divide

and

differentiate

into

any

cell

type,

they

can

be

used

to

replace

tissues

or

organs

required

by

patients.

Every

human

embryo

is

a

potential

human

being

and

should

be

given

the

chance

of

developing.

Cells

can

be

taken

from

embryos

that

have

stopped

developing

and

so

these

cells

would

have

died

anyway.


More

embryos

are

generally

produced

than

are

needed

and

so

many

are

killed.


Cells

are

taken

at

a

stage

when

the

embryos

have

no

nerve

cells

and

so

they

cannot

fee
l

pain.

There

is

a

risk

of

embryonic

stem

cells

developing

into

tumour

cells.