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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?.
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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 Replication • DNA 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 Cycler • instrument 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 DNA • Recombinant DNA relies on the ability of restriction enzymes • to cut DNA into fragments • can later be incorporated into another DNA strand. • Restriction enzymes • highly specialized scissors • cut 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 • Chymosin • found in rennet, which is an enzyme required to make cheese • Human Growth Hormone • administered to patients whose pituitary glands generate insufficient HGH • originally obtained from pituitary glands of cadavers • Hepatitis B vaccine • prevention of hepatitis B infection • Diagnosis of infection with HIV • each of the three widely used methods for diagnosing
DNA Typing • Tandem 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 repeats • but 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
