Docstoc

12-3 RNA and Protein Synthesis - Moreno Valley High School

Document Sample
12-3 RNA and Protein Synthesis - Moreno Valley High School Powered By Docstoc
					Chapter 12
DNA & RNA
Section 12-3
RNA & Protein Synthesis
Objectives
n   What are the three main types of RNA?

n   What is transcription?

n   What is translation?
The Structure of RNA
n   Long Chains of Nucleotides
    ¨5  Carbon Sugar ( Ribose )
    ¨ Phosphate Group
    ¨ Nitrogenous Base
      n   A, G, C, U ( no T )
    ¨ Single   Stranded
Types of RNA
   RNA Mostly For Protein Synthesis
        Three Types of RNA
Messenger RNA, mRNA

Ribosomal RNA, rRNA

Transfer RNA,   tRNA
Types of RNA
                  mRNA
  Template to construct protein from the DNA
                to the ribosome.
                   rRNA
          Part of ribosome structure
                   tRNA
Transports amino acids from cytoplasm to the
                 ribosomes
Transcription
The process of copying part of the DNA
       nucleotide sequence into a
   complementary sequence of RNA

Requires enzymes e.g. RNA Polymerase
RNA Polymerase
Transcription
Key Concept:
  During transcription, RNA
   polymerase binds to DNA and
   separates the DNA strands. RNA
   Polymerase then uses one strand
   of DNA as a template to
   assemble nucleotides into RNA
Transcription

Promoters
 ¨Regions  on DNA that show where
  RNA Polymerase must bind to begin
  the Transcription of RNA
 ¨Specific base sequences act as
  signals
 ¨Other base sequences indicate
  stopping points
Transcription

RNA Splicing
 ¨After the DNA is transcribed into RNA
  editing must be done to the
  nucleotide chain to make the RNA
  functional
 ¨Introns
   n Snippedout of the chain in the nucleus,
    non-functional segments
mRNA Splicing
RNA Splicing

          Exons

    Remaining, active
  segments of nucleotides
The Genetic Code
Proteins are long chains of amino acids.

   There are 20 different amino acids

The order of amino acids in the protein
   determine its shape and function
The Genetic Code
 There are 20 amino acids but only
          4 bases in RNA

          Adenine       A
          Cytosine      C
          Guanine       G
          Uracil        U
The Genetic Code

  The genetic code consists of
    “words” three bases long


Each “word” is called a Codon:
 three consecutive nucleotides that
     specifies a single amino acid
The Genetic Code
For Example:
UCGCACGGU = RNA Sequence
  UCG-CAC-GGU = Codons
     UCG codes for Serine
    CAC codes for Histidine
    GGU codes for Glycine
Code Wheel
The Genetic Code
4 Bases
  Codons Defined with 3 Bases
    There Are 64 Possible
    3-base codons

  Since there are only 20 amino acids,
  some amino acids are represented by
             multiple codons
             See Figure 12-17
Translation

 Translation is the process of of
    decoding the mRNA into a
       polypeptide chain

n Ribosomes
 ¨Read  mRNA and construct the
  proteins
Translation Step A
Translation Step B
Translation
Step C
  ¨ Ribosome    connects the
    amino acids together as
    they come into the
    ribosome
  ¨ Ribosome disconnects
    the the 3rd amino acid
    from the ribosome to
    float into the cytoplasm
Translation
n   Step D
    ¨ Polypeptide  chain
      grows until the
      mRNA STOP Codon
      is reached
    ¨ The ribosome then
      releases the
      polypeptide chain
      into the cytoplasm
The Roles of RNA & DNA

          DNA =
        Master Plan

          RNA =
Blueprints of the Master Plan
Genes & Proteins

n Genes  are instruction for
  assembling proteins
n Proteins are enzymes that catalyze
  and regulate chemical reactions
  ¨Pigments,  antigens, regulators
  ¨Proteins are keys to function

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:1
posted:9/11/2013
language:
pages:25