Nucleotide codes: What is a Codon?

Series of three nucleotides is called a codon.

What does a codon code for? Each codon codes for a

specific amino acid in a protein.

Amino acids are assembles into proteins

What do these codons have to do with proteins?

Each codon represents an amino acid that will eventually form a protein that is used within a cell.

Proteins are made up of hundreds of amino acids in a specific sequence.

When they get “out of order’ a mutation occurs.

Long string of amino acids will form

DNA ReplicationDNA duplicates itself

prior to cell division.

DNA replication begins with the unwinding of the DNA strands of the double helix.

Each strand is now exposed to a collection of free nucleotides that will be used to recreate the double helix, letter by letter, using base pairing.

PCR Many enzymes and proteins, such as DNA polymerases,

are involved in unwinding the DNA, keeping the DNA strands apart, and assembling the new DNA strands.

PCR is a technique for replicating small quantities of DNA or broken pieces of DNA found at a crime scene, outside a living cell.

sample size is no longer a limitation in characterizing DNA recovered at a crime scene

DNA Thermal Cyclerinstrument that automates the rapid and precise

temperature changes required to copy a DNA strand

Within a matter of hours, DNA can be multiplied a billionfold

How does DNA Replication begin?

unwinding of DNA

double helix is recreated with proper order of base pairs

PCR for replicating

Recombinant DNARecombinant DNA relies on

the ability of restriction enzymesto cut DNA into fragmentscan later be incorporated

into another DNA strand.

Restriction enzymes highly specialized scissorscut a DNA molecule when it

recognizes a specific sequence of bases.

Once a portion of the DNA strand has been cut

the next step in the recombinant DNA process is to insert the isolated DNA segment into a foreign DNA strand

usually that of a bacterium.

As the bacteria multiply rapidly, copies of the altered DNA are passed on to all descendants

Examples of Recombinant DNA

Human insulin

Chymosinfound in rennet, which is an enzyme required to make

cheese

Human Growth Hormoneadministered to patients whose pituitary glands

generate insufficient HGHoriginally obtained from pituitary glands of cadavers

Hepatitis B vaccineprevention of hepatitis B infection

Diagnosis of infection with HIVeach of the three widely used methods for diagnosing

DNA TypingTandem Repeats

Portions of the DNA molecule contain sequences of bases that are repeated numerous times

offer a means of distinguishing one individual from another through DNA typing.

seem to act as filler or spacers between the coding regions of DNA.

What is important to understand is that all humans have the same type of repeatsbut there is tremendous variation in the

number of repeats each of us have.

Figure 9-6  A DNA segment consisting of a series of repeating DNA units. In this illustration, the fifteen-base core can repeat itself hundreds of times. The entire RFLP segment is typically hundreds to thousands of bases long.

An example would be:

A-T-T-C-G-A-T-T-C-G-A-T-T-C-G

in which the sequence A-T-T-C-G is repeated three times

Such repeated sequences facilitate the genetic fingerprinting of individuals.an individual may inherit a certain number of

repeats at one locus from their mother, and a different number of repeats at the same locus, from their father.

http://www.rvc.ac.uk/review/DNA_1/4_VNTRs.cfm