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  • 1. DNA and RNA relationship
    • A gene is a genetic sequence that codes for an RNA .
    • In protein coding genes, RNA codes for a protein.
  • 2.
    • During protein synthesis a working copy of the code is made from RNA
    • Overall scheme: DNA -> RNA -> protein
  • 3.
    • HOW ?
  • 4. Processes involving the two..
    • TRANSCRIPTION = The transfer of the coded information from the nucleus to the cytoplasm.
    • TRANSLATION = The conversion of that info into polypeptides on ribosomes.
    • Both these reaction involves DNA + RNA .
  • 5. Transcription
    • nucleus.
    • major components = DNA, RNA polymerase 
    • Importance = Gene is activated.
    • = A copy of the code is made from RNA (m-RNA)
    • = m-RNA leaves the nucleus, goes to cytoplasm. 
  • 6. Transcription
    • Formation of m-RNA molecule
    • RNA polymerases
    • Separate the 2 DNA strands and link RNA nucleotides as they base pair along the DNA template
    • Can only add nucleotides to the 3' end; thus mRNA goes in the 5' to 3' direction
  • 7. Translation
    • cytoplasm, on the ribosomes m-RNA
    • Major components = Ribosomes Peptidyl transferase enzyme Transfer RNAs 
    • Importance = Ribosome decodes the m-RNA and makes the correct protein.
  • 8. Transcription
      • a Working Copy of the Code is Made From RNA
    • The RNA copy of the code is complementary:
    •   DNA Base RNA Base  A U, C G, G C, T A
    • Note that U replaces T in RNA (U = uracil)
    • RNA leaves the nucleus and goes into the cytoplasm, attaches to a ribosome to make protein (translation)
  • 9. Transcription…
    • DNA acts as template for the synthesis of RNA
    • RNA polymerase attaches to the double helix.
    • H+ bonds are broken = DNA unwinds.
    • Coding strand acts as a template and is copied by base pairing of nucleotides.
    • A complementary polynucleotide strand of mRNA is built.
    • The mRNA detaches and leaves the nucleus through the nuclear membrane pore.
    • In the cytoplasm, mRNA becomes attached to ribosomes .
  • 10.  
  • 11. Close up…
    • Eukaryotic genes contains 2 regions: “exons” and “introns”.
    • Exons – code for amino acids.
    • Introns - DO NOT . Fx?
    • During transcription, both E+I are copied from the DNA.
    • DNA sequence coding for proteins exons may be interrupted by non coding DNA i ntrons.
  • 12. During RNA synthesis, non-coding sequences of base pairs needs to be subtracted from the coding sequences of a gene in order to transcribe DNA into (mRNA.) So that.. mRNA that leaves now consists of a continous coding region
  • 13.
    • Before mRNA leaves the nucleus, introns are removed
  • 14. RNA splicing..
    • Process to remove unwanted materials.
    • i. In the nucleus, DNA that includes the E + I is first transcribed into a complementary nuclear RNA copy (nRNA)
    • ii. Introns are removed from nRNA by a process called RNA splicing.
    • The edited sequence is called mRNA
  • 15. Vital steps
    • Initiation
    • Elongation
    • Termination
  • 16. Transcription
    • Initiation
    • RNA polymerases bind to DNA at promoters (initiation site);
    • Enzyme separates the 2 DNA strands and transcription begins
    • Elongation
    • RNA polymerases move along the DNA
    • 1- untwists and opens a short segment of DNA (DNA template)
    • 2- links incoming RNA nucleotides to the 3' end the elongating strand
    • 1 at a time in the 5' to 3' direction
    • the non-coding strand of DNA reforms a DNA-DNA double helix by pairing with the coding strand
  • 17. Termination
    • RNA polymerases reaches a termination site on the DNA
    • RNA molecule is then released