Nucleotide codes
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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.

Nucleotide codes


  • 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.

Nucleotide codes

  • 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.

Nucleotide codes

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.

Nucleotide codes

  • 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.


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