Download DNA Technology - 2 What are plasmids?

DNA Technology - 2
What are plasmids?
Small, circular DNA molecules
(Found in bacteria)
They are separate from the bacterial chromosome
Why are plasmids useful?
They are used to manipulate genes in the lab
They are small
Contain genes useful to the bacteria
And, are easily taken up by bacterial cells
When they are taken up they are called vectors
What happens when the bacterial cell
replicates its chromosome?
It also replicates the plasmid DNA
(including any foreign DNA as well)
vector A DNA carrier that move genes from one cell to another
What does cutting and pasting
of DNA mean?
 Enzymes are involved
e.g., A T C G
For cutting, what are they called?
Restriction enzymes
They recognize specific sequence of: A T C G
Hundreds have been isolated from bacteria
For pasting, what are they called?
DNA ligases
Its the last step to make recombinant DNA
They bind cut ends back together
(by covalent bonds between adjacent nucleotides)
So, this cutting and pasting of DNA
is used to:
Cut gene sequence of interest (e.g., from human DNA)
Enzyme name?
Cut a plasmid (from a bacterium)
Enzyme name?
Create a recombinant DNA molecule
By using the plasmid
And ‘pasting’ a human gene sequence into it
Enzyme name?
Polymerase Chain Reaction
Or PCR
• PCR is a technique
• In which any segment of DNA
can be copied
• Quickly and precisely
Why is it so important?
Use minute amounts of blood or other tissue
To generate enough DNA for analysis
e.g., DNA from the follicle of ONE stand of hair
How does PCR work?
Make a mixture of:
• the DNA sample,
• some nucleotides,
• an enzyme, DNA polymerase
Treat the mixture to:
• cycles of heating
Allows separation of DNA strands
• cycles of cooling
Allows DNA strands to re-form duplexes
DNA Replication occurs during cooling cycle
In each cycle, the DNA is DOUBLED
How many copies of DNA after each cycle?
How many copies after a 5th cycle?
___1st cycle
Within a few hours:
___2nd cycle
PCR can generate billions of copies
From a SINGLE DNA molecule
___3rd cycle
___4th cycle
Enough to do extensive analyses
The Human Genome Project
1990 - 2003
What was the goal of HGP?
To determine the nucleotide sequence all the DNA
In any given human cell
To identify the location & sequence of every gene
What was discovered?
Our DNA contains ~ 2.9 billion nucleotide pairs
About 25,000 genes
There is a LOT of DNA that isn’t made up of genes
About 97% is non-coding DNA
Learning check
1. Why is only the slightest trace of DNA at a crime
scene often sufficient for forensic analysis?
2. A carrier that moves DNA from one cell to
another, such as a plasmid, is called a ________
3. What features of a DNA fragment causes it to move
through a gel during electrophoresis?
a.
b.
c.
d.
Its nucleotide sequence
The hydrogen bonds between its base pairs
Its double helix shape
The electrical charges of its phosphate groups
4. A paleontologist has recovered a bit of organic
material from the 400 year old preserved skin of an
extinct dodo. She would like to compare DNA from
the sample with DNA from living birds. The most
useful method for increasing the amount of dodo
DNA available for testing is __________
5. Why is golden rice pale yellow in color?
a It is rich in chlorophyll a.
b It is nutrient-poor.
c It is rich in beta-carotene.
d It is rich in chlorophyll b.
e It is rich in phycobilins.
What does this figure show?
2
4
7
3
1
5
What does each ‘band’ consist of?
8
6
Some Review
Structure and Function?
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2.
3.
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Name molecule
Name molecule
Name molecule
Name the reaction
5.
6.
7.
8.
9.
Name of molecule
What does the arrow refer to?
Name of molecule
Name of molecule
Where does this take place?
15
4
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1
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9
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