DNA Technology - 2

What are plasmids?

Small, circular DNA molecules

They are separate from the bacterial chromosome

(Found in bacteria)

Why are plasmids useful?

They are small

And, are easily taken up by bacterial cells

When they are taken up they are called vectors

vector A DNA carrier that move genes from one cell to another

They are used to manipulate genes in the lab

What happens when the bacterial cell replicates its chromosome?

It also replicates the plasmid DNA

Contain genes useful to the bacteria

(including any foreign DNA as well)

What does cutting and pasting of DNA mean?

Enzymes are involved

For cutting, what are they called?

Restriction enzymes

For pasting, what are they called?

DNA ligases

They recognize specific sequence of: A T C G

e.g., A T C G

Hundreds have been isolated from bacteria

They bind cut ends back together

(by covalent bonds between adjacent nucleotides)

Its the last step to make recombinant DNA

So, this cutting and pasting of DNA is used to:

Cut gene sequence of interest (e.g., from human DNA)

Cut a plasmid (from a bacterium)

Create a recombinant DNA molecule

By using the plasmid

And ‘pasting’ a human gene sequence into it

Enzyme name?

Enzyme name?

Enzyme name?

Polymerase Chain Reaction

Or PCR

• In which any segment of DNA can be copied

• Quickly and precisely

• PCR is a technique

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 coolingAllows DNA strands to re-form duplexes

DNA Replication occurs during cooling cycle

Within a few hours:

In each cycle, the DNA is DOUBLED

___1st cycle

___2nd cycle

___3rd cycle___4th cycle

How many copies of DNA after each cycle?

How many copies after a 5th cycle?

PCR can generate billions of copiesFrom a SINGLE DNA molecule

Enough to do extensive analyses

The Human Genome Project

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

1990 - 2003

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. Its nucleotide sequenceb. The hydrogen bonds between its base pairsc. Its double helix shape d. 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.

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What does each ‘band’ consist of?

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What does this figure show?

Some Review

Structure and Function?

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1. Name molecule2. Name molecule3. Name molecule4. Name the reaction

5. Name of molecule6. What does the arrow refer to?7. Name of molecule8. Name of molecule9. Where does this take place?

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