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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
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
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 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.
  • 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
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
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
  • 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
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
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:


  • 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.