DNA Transcription and Translation - PowerPoint

							  DNA Transcription
   and Translation
How are proteins made from the
          DNA code
       Components of DNA
Nucleotide = nitrogenous base
           + 5-carbon sugar
           + phosphate
    Step One: Protein Synthesis
1. Copy DNA into RNA
What is RNA?

DNA                     RNA
deoxyribonucleic acid   ribonucleic acid

sugar is deoxyribose    sugar is ribose
double stranded         single stranded
contains thymine        contains uracil
1 type                  3 types
            Types of RNA
Messenger RNA (mRNA) – carries the DNA
 “message” from nucleus to the rest of the
 cell
                    Types of RNA
Messenger RNA (mRNA) – carries the DNA “message” from nucleus to the rest
  of the cell

Ribosomal RNA (rRNA) – ribosomes, where
  proteins are assembled, are made of RNA
                    Types of RNA
Messenger RNA (mRNA) – carries the DNA “message” from nucleus to the rest
   of the cell
Ribosomal RNA (rRNA) – ribosomes, where proteins are assembled, are made
   of RNA

Transfer RNA (tRNA) – transfers amino
  acids (components that make up proteins)
  to the ribosome where they are assembled
  into a protein chain
     Step Two: Transcription
2. Like replication DNA is unwound and a
  copy is made…this time it is made into
  RNA strand NOT an identical DNA strand.




                                 Similar to figure
                                 12.14 in text
              Promoters
• How does cell know where to start
  transcribing DNA into RNA (and where to
  stop)?
• There are “start” areas called promoters
  and “stop” areas
         Step Three: Editing
3. Pieces of the RNA (introns) are removed
  (these are currently thought to be
  nonfunctional) and then it is reassembled
  with just the exons
      Step Four: Translation
4. RNA needs to be translated into amino
  acids. Amino acids are then strung
  together and…
Voila! A protein is made!
(Ok, but it’s kind of complicated)
          The Genetic Code
• Proteins are made by
  joining amino acids
  into strands called
  polypeptides
• There are 20 different
  amino acids
• Genetic code is read
  in groups of 3 bases
• Each group of 3 bases
  is a codon
• Each codon
  corresponds to an
  amino acid
                             Fig. 12.17 in text
       How to use the code…
Glycine is coded for by
  GGU, GGC, GGA, or       See glycine again here? (a
  GGG                       different way to show the
                            same code)
  Try to translate this code…
           Use Fig 12.17 in text

      AUGUCUCGACGUGGGUAG

Start, Serine, Arginine, Arginine, Glycine, Stop


AUG…UCU…CGA…CGU…GGG…UAG