HOW GENES WORK

Transcription
1. Transfer of genetic info into an INTERMEDIATE message, which CARRIES the info to the RIBOSOME (protein-synthesizing factory) where a PROTEIN is made by TRANSLATION
2. DNA --> RNA
  1. DNA = 4 letters = A,T,G,C
  2. RNA = 4 letters = A,U,G,C
3. 3 types of RNA transcribed from genes by RNA polymerase
  1. mRNA (messenger RNA)
    1. each is a POLYMER OF NUCLEOTIDES that contain info to be CONVERTED by TRANSLATION INTO A POLYPEPTIDE (protein)
  2. tRNA (transfer RNA)
    1. TRANSPORT specific amino acids to the RIBOSOME, the protein synthesizing complex (like trucks)
      1. Each has a different amino acid on it and has a slightly different structure
      2. Activating enzymes put the specific amino acid onto the specific tRNA end
      3. Down in the anticodon loop, there's a string of 3 nucleotides that are SPECIFIC to the tRNA which are complementary to the bases in the codon that is complementary to the other string of nucleotides.
      4. Amino acid does NOT interact directly with the codon
      5. Base pairing between anticodon and codon because there's a tRNA in between! Goes on in the ribosome.
  3. rRNA (ribosomal RNA)
    1. complexed with proteins to FORM ribosome
      1. Ribosome is the site of protein synthesis
        contains sites where RNA can sit in the ribosome
        2 subunits
Translation
1. RNA --> Protein
  1. RNA = 4 letters = A,U,G,C
  2. Protein = 20 letters = amino acids
2. Initiation
  1. Binding site = certain site of mRNA where it doesn't get translated
  2. Initiator tRNA comes in carrying Met (start) cause it has the complementary base
  3. Requires energy
  4. Elongation
    1. where polypeptide gets elongated
    2. Termination
      1. Protein release factor triggers a dissociation of the whole complex so the polypeptide is released, tRNA is released, and the ribosome subunits separate
The genetic code
1. Triplets of nucleotides are called CODONS b/c they code for specific amino acids
2. UNIVERSAL
3. Redundancy --> genetic code is DEGENERATE
4. Consists of nucleotide bases that are read LINEARLY, 3 at a time, the sequence of each TRIPLET (codon) specifying an AMINO ACID
  1. Hydrogen bonding between DNA and RNA
DNA --> Protein (polypeptides)
1. Enzymes can catalyze formation of bonds between chromosomes
2. Enzymes are involved in metabolism of the cell
  1. Metabolism can be divided into 2 pathways
    1. Catabolic pathways
      1. Break things down
      2. Substrate --> B+C
    2. Anabolic pathways
      1. Build things up
      2. A --> B --> C--> D--> end product
        at each step, there's an enzyme/polypeptide required
Stages in gene expression
Structure of a gene
1. Coding sequences recognized by RNA polyermase:
  1. Start --> stop
    1. START = PROMOTER
      1. Why doesn't it start anywhere?
        Because we want a SPECIFIC sequence of nucleotides to occur in the message so that it'll appear in the polypeptide
      2. RNA polymerase binds, and the DNA strand is broken open so the base is free in the template strand for complementary base pairing with the newly synthesized RNA
      3. Initiation of transcription by RNA polymerase: PROMOTER RECOGNITION
        1) RNA polymerase moves along DNA until it reaches PROMOTER. Binds tightly and opens up the double helix.
        2) Nucleoside triphosphate with a complementary base comes along and bonds via HYDROGEN BONDING
        Elongation
        Process of incorporating nucleotides into the TRANSCRIPT
        RNA polymerase keeps moving down the gene at each DNA base in the template. Newly synthesized strand of RNA is being made in the 5' --> 3' direction.
        Termination
        RNA polymerase falls off the DNA and releases the completed RNA transcript.
    2. STOP = TERMINATOR
  2. Puts polymers of RNA nucleotides together
More types of genes, than there are those that code for proteins

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	Creado por julia guk hace más de 9 años