Zusammenfassung der Ressource
HOW GENES WORK
- Transcription
- 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
- DNA --> RNA
- DNA = 4 letters = A,T,G,C
- RNA = 4 letters = A,U,G,C
- 3 types of RNA
transcribed from genes
by RNA polymerase
- mRNA (messenger RNA)
- each is a POLYMER OF
NUCLEOTIDES that
contain info to be
CONVERTED by
TRANSLATION INTO A
POLYPEPTIDE (protein)
- tRNA (transfer RNA)
- TRANSPORT
specific amino
acids to the
RIBOSOME,
the protein
synthesizing
complex (like
trucks)
- Each has a different amino acid on it and has a slightly different structure
- Activating enzymes put the specific
amino acid onto the specific tRNA
end
- 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.
- Amino acid does NOT interact directly with the codon
- Base pairing between anticodon and codon
because there's a tRNA in between! Goes on
in the ribosome.
- rRNA (ribosomal RNA)
- complexed with proteins to FORM ribosome
- Ribosome is the site of protein synthesis
- contains sites where RNA can sit in the ribosome
- 2 subunits
- Translation
- RNA --> Protein
- RNA = 4 letters = A,U,G,C
- Protein = 20 letters = amino acids
- Initiation
- Binding site = certain site of mRNA where it doesn't get translated
- Initiator tRNA comes in carrying Met (start) cause it has the complementary base
- Requires energy
- Elongation
- where polypeptide gets elongated
- Termination
- 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
- Triplets of nucleotides are
called CODONS b/c they
code for specific amino acids
- UNIVERSAL
- Redundancy --> genetic code is
DEGENERATE
- Consists of nucleotide bases that are read
LINEARLY, 3 at a time, the sequence of each
TRIPLET (codon) specifying an AMINO ACID
- Hydrogen bonding between DNA and RNA
- DNA --> Protein (polypeptides)
- Enzymes can catalyze formation
of bonds between chromosomes
- Enzymes are involved in metabolism of the cell
- Metabolism can be divided into 2 pathways
- Catabolic pathways
- Break things down
- Substrate --> B+C
- Anabolic pathways
- Build things up
- A --> B --> C--> D--> end product
- at each step, there's an
enzyme/polypeptide required
- Stages in gene expression
- Structure of a gene
- Coding sequences
recognized by
RNA polyermase:
- Start --> stop
- START = PROMOTER
- 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
- 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
- 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.
- STOP = TERMINATOR
- Puts
polymers of
RNA
nucleotides
together
- More types of genes, than there are those that code for proteins