RNA and Protein Synthesis - pcmac

Document Sample
RNA and Protein Synthesis - pcmac Powered By Docstoc
					RNA and Protein Synthesis




                            1
            The Function of DNA
• The DNA molecule
  contains all of your
  hereditary information in
  the form of genes.
• Genes are portions of the
  DNA molecule that code
  for the production of
  specific types of proteins.
• However, DNA is confined
  to the nucleus, while
  proteins are made by
  ribosomes in the
  cytoplasm.
• Thus, a messenger             http://www.accessexcellence.org/RC/VL/GG/images/genes.gif


  molecule is needed.
                                                                                            2
        Comparing DNA and RNA
• RNA is the nucleic acid that
  acts as a messenger
  between DNA and the
  ribosomes.
• The RNA produced during
  transcription is structurally
  different from DNA in 3
  basic ways:
   – 1. The sugar in RNA is ribose
     whereas the sugar in DNA is
     deoxyribose.
   – 2. RNA is single stranded
     while DNA is double stranded.
   – 3. RNA contains a base called
     uracil instead of thymine.      http://www.dkimages.com/discover/previews/769/85011519.JPG
                                                                                                  3
         The Role of RNA
• RNA molecules have many functions, but
  in the majority of cells, most RNA
  molecules are involved in protein
  synthesis.
• Protein synthesis is the assembly of
  amino acids into proteins.



                                           4
                       Types of RNA
• The RNA produced during transcription is modified into 3 basic
  types:
   – 1. messenger RNA (mRNA) is responsible for copying one strand of
     DNA in the nucleus and carrying that information to the ribosomes in the
     cytoplasm.
   – 2. ribosomal RNA (rRNA) makes up a large part of the ribosome and is
     responsible for reading and decoding mRNA.
   – 3. transfer RNA (tRNA) carries amino acids to the ribosome where they
     are joined to form proteins.




                                                                                                         5
                        http://images.encarta.msn.com/xrefmedia/zencmed/targets/illus/ilt/T068340A.gif
          Protein Synthesis
• During protein synthesis, genes copied
  onto RNA are expressed by the production
  of specific types of proteins.
• Protein synthesis involves two processes:
  – 1. Transcription – the process where a portion
    of the DNA sequence is copied into a
    complementary RNA sequence.
  – 2. Translation – the decoding of an mRNA
    message into a polypeptide chain (protein).
                                                 6
  Transcription and Translation
• Transcription occurs   • Translation is
  on the DNA in the        completed by the
  nucleus.                 ribosomes located in
• Transcription Demo       the cell’s cytoplasm.
                         • All three types of RNA
                           work together during
                           translation to produce
                           polypeptides
                           (proteins).

                                                7
              Decoding mRNA
• The sequence of bases in an mRNA molecule
  serves as instructions for the order in which amino
  acids are joined to produce a polypeptide.
• Ribosomes decode these instructions by using
  codons, sets of 3 bases that each code for 1 amino
  acid.
• Each codon is matched to an anticodon, or
  coplementary sequence on the tRNA to determine
  the order of the amino acids.
• Translation Demo




                              http://www.gwu.edu/~darwin/BiSc150/One/codon.gif
                                                                                 8
                                                           Using a Codon Chart
                           • A codon chart can be used to determine
                             the sequence of the amino acids in the
                             polypeptide.
                           • The mRNA bases or CODONS are used
                             to find the amino acid.
http://www.safarikscience.org/biologyhome/7_dna/codon_qu
estion.png




                                                                                 9
                 Decoding Practice
• For the following examples, give the appropriate
  mRNA sequence and amino acid sequence.
  (Remember: U replaces T in mRNA.)

 Example 1:
 DNA:            TAC GCA TGG AAT
 mRNA:           AUG CGU ACC UUA
 Amino Acids:    Met    Arg   Thr   Leu

  Example 2:
  DNA:           CGT GGA GAT ATT
  mRNA:          GCA CCU CUA UAA
  tRNA:          CGU GGA GAU AUU
  Amino Acids:    Ala   Pro   Leu   stop
                                                     10
    What is a gene mutation?
• Sometimes during replication, an error is
  made that causes subsequent changes in
  the mRNA and proteins that are made
  using that DNA.
• These errors or changes are called
  mutations.



                                              11
    Types of Gene Mutations
• Point mutation:
  – changes in only 1 or a few nucleotides of
    DNA.
  – Substitutions, in which one base is changes
    to another, are a type of point mutation.
• Frameshift mutation:
  – When one base is deleted (deletion) or
    added (insertion) into a DNA sequence.
  – This causes the entire sequence of codons to
    shift over by one base.
                                               12
What are Chromosomal Mutations?
• Mutations involving a long segment of
  DNA.
  – These mutations can involve deletions,
    insertions, or inversions of sections of DNA.
  – In some cases, deleted sections may attach to
    other chromosomes, changing both the
    chromosomes that lost the DNA and the one
    that gained it, also called a chromosomal
    rearrangement.

                                               13
     What is the significance of
            mutations?
• Mutations in DNA cause changes in the
  sequence of amino acids which ultimately
  creates changes in proteins and their
  function.




                                             14

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:0
posted:4/9/2013
language:Unknown
pages:14