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DNA and Protein Synthesis

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DNA and Protein Synthesis DNA Does 2 Important Things in a Cell: 1)DNA is capable of replicating itself. Every time a cell divides, each DNA strand makes an exact ... – PowerPoint PPT presentation

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Title: DNA and Protein Synthesis


1
DNA and Protein Synthesis
2
DNA Does 2 Important Things in a Cell
  • 1)DNA is capable of replicating itself. Every
    time a cell divides, each DNA strand makes an
    exact copy of itself.
  • 2)DNA directs the production of proteins in the
    cell. DNA contains the instructions on how to
    make proteins.

3
The Importance of Proteins
  • Proteins are the workhorses of the cell. They
    build all of the important structures and carry
    on most of the important cellular functions.
  • What types of proteins are made determine
    everything about the organism and how it
    functions.

4
Review of Protein Structure
  • Proteins are large polymers made of long chains
    of amino acids.
  • Amino Acids bind together with peptide bonds.
  • A proteins final shape determines its function.
    This shape is determined by its amino acid
    sequence.

5
Protein Structure
  • Proteins are made by ribosomes.
  • Amino acids are put together in a long chain
    which then folds and bends to determine the final
    shape.
  • Remember Shape equals function!
  • So, it is VERY important that the amino acid
    sequence is correct!

6
What determines the correct amino acid sequence
in a protein?
  • The DNA in a cell determines the sequence of
    amino acids in a protein.
  • The DNA sequence is a code that determines which
    amino acid is first, which is second, etc.

DNA determines protein
7
DNA leads from afar..
  • The DNA in a cells nucleus determines the
    sequence of amino acids that are put together at
    the ribosome.
  • Yet, the DNA never leaves the nucleus!
  • How does the DNA do this?

8
Chromosomes to Genes
9
Messenger RNA (mRNA)
  • DNA is able to tell the ribosome how to build
    the protein by sending a messenger.
  • This comes in the form of an RNA molecule.
  • Therefore, this is called messenger RNA, or mRNA.

10
From DNA to Protein
  • Protein Synthesis has 2 main processes
  • 1) Transcription (to write) making a mRNA
    molecule
  • 2) Translation (to read) making the protein,
    using the mRNA as a guide.
  • Together, these are called Gene Expression

11
RNA A Major Player
  • Three types of RNA are used in protein building
  • mRNAmessenger RNA (made in nucleuscarries the
    genetic code)
  • tRNAtransfer RNA (brings amino acids to the
    ribosome)
  • rRNAribosomal RNA (what ribosomes are made of)

Ribonucleic Acid
12
RNA Vs. DNA
  • RNA differs from DNA in 3 ways
  • RNA is single-stranded DNA is double-stranded
  • RNA has Ribose DNA has Deoxyribose
  • RNA has Uracil DNA has Thymine

Uracil is found in RNA only
13
  • RNA Vs. DNA

14
Transcription Reading the Gene
  • During transcription, the information in a
    particular segment of DNA (a gene) is copied into
    mRNA
  • Step 1
  • RNA polymerase binds to a specific sequence of
    bases on the DNA called the Promoter. This is the
    start code.

15
Transcription Reading the Gene
  • Step 2 Helicases unwind the DNA strand in front
    of the promoter region.
  • Step 3 RNA polymerase adds and links
    complementary RNA bases on one side of the DNA,
    following base pairing rules. (Exception Adenine
    in DNA bonds to Uracil)

16
Transcription
  • The RNA polymerase eventually reaches a stop
    location in the DNA.
  • This stop signal is a sequence of bases that
    marks the end of each gene.
  • The result is a single strand of RNA

17
The Genetic Code
  • To make a correct protein, the amino acids must
    be put in the proper sequence.
  • Each segment of 3 nucleotides in DNA codes for 1
    amino acid.
  • Each triplet of DNA bases makes a triplet of mRNA
    basescalled a Codon.

18
Codons of mRNA
What amino acid comes from the code AUC? GGG? CGA?
19
Translation RNA to Proteins
  • Translation is the process of converting the
    language of RNA into the language of proteins
    (amino acid sequences.)
  • Translation involves mRNA, tRNA, and rRNA.

20
tRNA Transfer RNA
  • Each tRNA is folded into a compact shape.
  • There are 2 important places on each tRNA
  • Terminal endhas 3 bases which match up to mRNA.
    This is the Anticodon.
  • Amino Acid attachment site

21
Translation, Step 1 Start Codon
  • After leaving the nucleus, the mRNA joins with a
    ribosome and tRNA.
  • The mRNA start codon, AUG, signals the beginning
    of a protein.
  • The tRNA carrying Methionine binds to the start
    codon.

22
Translation Step 2A new tRNA arrives.
  • A new tRNA arrives and binds to the next codon on
    the mRNA.
  • A peptide bond forms between the first amino acid
    and the second amino acid.
  • The first tRNA detaches and leaves its amino acid
    behind.

23
The Ribosome Moves down the mRNA
  • The ribosome moves one codon down the mRNA
    strand.
  • Because the anticodon (on the tRNA) is attached
    to the codon, they move together as a unit.
  • The amino acid chain grows as each new one binds.

24
Translation, Step 3 Releasing the protein
  • The process ends when a stop codon is reached.
  • The amino acid chain is released, the ribosome
    complex and mRNA strand fall apart.

25
Protein Synthesis Animations
  • http//bioweb.uwlax.edu/genweb/molecular/theory/tr
    anslation/trans1.swf
  • http//www.youtube.com/watch?v983lhh20rGYfeature
    related
  • http//www.youtube.com/watch?NR1featureendscree
    nvIkq9AcBcohA
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