Transcrption
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Transcrption

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Transcrption Transcrption Presentation Transcript

  •  
  • TRANSCRIPTION BY SHUMAILA IQBAL BS[MLT3RD YEAR] 6TH SEMISTER
  • INTODUCTION.
    • The biosynthesis of RNA, called transcription .
    • RNA synthesis, or transcription, is the process of transcribing DNA nucleotide sequence information into RNA sequence information
    View slide
  • WHAT IS RNA?
    • RNA is a polymer composed of alternating units of ribonucleotides connected through a 3’-5’ phosphodiester bond.
    • It is a single stranded nucleic acid that involves in protein synthesis.
    View slide
  • WHAT IS RNA.?
    • In contrast with DNA, ribonucleotides contain:
    • Hydroxl group on the 2’ carbon of the ribose sugar.
    • The base uracil in place of thymine.
  • TYPES OF RNA.
    • There are three major types of RNA:
    • Ribosomal RNA.
    • Transfer RNA.
    • Messenger RNA.
  • TYPES OF RNA.
    • Minor types:
    • Small nuclear RNA.
    • Small interfering RNA.
    • Micro RNAS.
    • Other small RNAS.
  • RIBOSOMAL RNA.
    • Ribosomal RNA (rRNA)-is the most abundant form of RNA,
    • nucleotides are in a globular form,
    • combine with proteins to make ribosomes.
    • Ribosomes- are organelles where proteins are made
  • TRANSFER RNA.
    • Transfer RNA (tRNA)- consist of a single chain of about 80 RNA.
    • nucleotides folded into a hairpin shape that binds to specific aminoacids.
    • Adopter molecule that carry specific amino acid to the ribosome.
  • MESSENGER RNA.
    • Messenger RNA (mRNA)- consists of RNA nucleotides in the form of a single uncoiled chain.
    • carries genetic information from the DNA
    • in the nucleus to the cytosol of a eukaryotic cell.
  • DNA TRANSCRIPTION
    • DNA is transcribed into RNA by DNA-dependent RNA polymerase (usually just called RNA polymerase ).
    • After binding to its start site in DNA, a specific sequence of base called the promoter, RNA polymerase & its supporting accessory proteins synthesize RNA using the base sequence of one strand of double helix DNA.
  • Transcription requirements
    • Transcription requires:
    • a promoter sequence on a DNA template.
    • RNA polymerase and accessory transcription factors.
    • Nucleotide triphosphates.
  • promoter sequence
    • A region on the DNA that determines the specificity of transcription of a particular gene.
    • Promoters contain specific DNA sequences and response elements which provide a binding site for RNA polymerase and for proteins called transcription factors that recruit RNA polymerase.
  • RNA polymerase
    • is a complex multisubunit enzyme, responsible for the transcription .
    • interacts with the promoter regions of genes as well as with a variety of elements and transcription factors to determine essentially all of the parameters that govern transcription.
  • Classess of RNA polymerase.
    • RNA polymeraze 1 : synthesizes the precursor of rRNA named pre rRNA .
    • RNA polymerase 2: synthesizes pre mRNA.
    • RNA POLYMERASE 3: synthesizes pre Trna.
    • All these enzymes synthesize what is called primary transcript or immature RNAs (pre form) which by some modifications occur after transcription, will give the mature rRNA, mRNA and tRNA.