In Vivo Gene Cloning - The Use Of Vectors Flashcards Preview

Biology-21-Recombinant DNA technology > In Vivo Gene Cloning - The Use Of Vectors > Flashcards

Flashcards in In Vivo Gene Cloning - The Use Of Vectors Deck (27)
Loading flashcards...

What are the two ways in which a gene can be cloned for medial or commercial use

In vivo - transferring the fragments to a host cell using a vector

In vitro - using the polymerase chain reaction


How do we use sticky ends to
Combine DNA from different sources

Restriction endonuclease cuts out a dna fragment

DNA from other source is added ( DNA from other source cut with same restriction endonuclease)

DNA Ligase joins the two sections

Making recombinant DNA


Why are sticky ends important

Because provided the same restriction is used, we can combine the DNA of one organism with that of any other organism


What are the sequences of DNA that are cut by restriction endonucleases are called

Recognition sites


How is the DNA fragment prepared for insertion

It involves the addition of extra lengths of dna.


What happens for the the transcription of any gene to take place

the enzyme that synthesise mRNA (rna polymerase) must attach to the DNA near a gene


What’s the binding site for rna polymerase

Region of DNA, known as promoter


What is essential if we want our dna fragment to transcribe mRNA in order to make a protein

That we attach it to the necessary promoter region to start the process


What’s a terminator

releases rna polymerase and ends transcription.


Why do we need a terminator

To stop transcription at the appropriate point


What is the vector used for. Give an example

Transport the DNA into the host cell

A plasmid


Where are the endonucleases used to do in the plasmid

They are used at one of the antibiotic resistance genes to break the plasmid loop


The restriction endonuclease used for the plasmid is the same as the one that cut of the DNA fragment. What does this ensure

That the sticky ends of the opened up plasmid are complimentary to the sticky ends of the DNA fragment.


What happens when the DNA fragments are mixed with with opened up plasmids

They become incorporated into them

Where they are incorporated, the join is made permanent using the enzyme DNA ligase. These plasmids now have recombinant dna


What happens during transformation

Introduction of DNA fragment into suitable host cell


Describe transformation

It involves the plasmids and bacterial cells being mixed together in a medium containing calcium ions.

The calcium ions, and changes in temperature, make the bacterial membrane permeable, allowing plasmids to pass through the cell surface membrane into the cytoplasm


What are the reasons for not all bacterial cells possessing the DNA fragments with the desired gene for the protein.

Only a few bacterial cells take up the plasmids when the two are mixed together

Some plasmids will have closed up again without incorporating the DNA fragment

Sometimes the DNA fragment ends join together to form its own plasmid


The first task is to identify which bacterial cells have taken up the plasmid. How do we do this

Using the fact bacteria have evolved mechanisms for resisting the effects of antibiotics, typically by producing an enzyme that breaks down the antibiotic before it can destroy the bacterium. The genes for the production of these enzymes are found in plasmids


Describe the process of finding out which bacterial cells have taken up the plasmids entail using the gene for antibiotic resistance, which is unaffected by the introduction of the new gene

All the bacterial cells are grown on a medium that contains the antibiotic ampicillin

Bacterial cells that have taken up the plasmids will have acquired the gene for ampicillin resistance

These bacterial cells are able to break down the ampicillin and therefore survive

The bacterial cells that have not taken up the plasmids will not be resistant to ampicillin and therefore die


What do marker genes do

They identify whether a gene has been take up by bacterial cells. They all involve using a second, separate gene on the plasmid.


How is the second gene easily identifiable for one reason or another. For example what...?

It may be resistant to an antibiotic

It may make a fluorescent protein that is easily seen

It may produce an enzyme whose action can be identified


What does replica plating do

It identifies those cells with plasmids that have taken up the new gene

It uses the other antibiotic resistance gene in the plasmid: the gene that was cut in order to incorporate the required gene.


What’s a positive of replica plating

It is possible to identify living colonies of bacteria containing the required gene


How are fluorescent markers used from the transfer of a gene from a jellyfish into the plasmid

The gene in question produces a green fluorescent protein. (GFP

The gene to be cloned is transplanted untinthr centre of the GFP gene.

Any bacterial cell that has been take up the plasmid with the gene that is to be cloned will not be able to produce GFP

Bacterial cells that have not taken up the gene will continue to produce GFP and to fluoresce. Unlike the cells that have not taken up the gene, these cells have taken it up will not fluoresce

As the bacterial cells with the desired gene are not killed, there is no need for replica plating.

Results can be obtained by simply viewing the cells under a microscope and retaining those that do not fluoresce. This makes the process more rapid


Describe how the enzyme marker lactase works

It will turn a Particular colourless substrate blue.

Again, the required gene is transplanted into the gene that makes lactase.

If a plasmid with the required gene is present in a bacterial cell, the colonies grown from it will not produce lactase.

Therefore when these bacterial cells are grown on the colourless substrate they will be unable to change its colour.

Where the genes has not been take up by the bacteria, they will not turn the substrate volume. These bacteria can be discounted



To show which cells (bacteria) have taken up the plasmid (gene)



Results can be obtained more easily and quickly - because, with antibiotic resistance markers, the bacterial cells with the required gene are killed, so replica plating is necessary to obtain the cells with the gene. With fluorescent gene markers, the bacterial cells are not killed and so there is no need to carry out replica plating