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Biology 1201A Study Guide - Midterm Guide: Start Codon, Peptide, Transfer RnaPremium

3 pages67 viewsFall 2016

Course Code
Biology 1201A
Vera Tai
Study Guide

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Biology 1201 Test 1 Outcomes Part 5
Central Dogma, Basic concepts associated with protein synthesis (transcription, translation, codons,
genetic code, link between genes and proteins)
Transcription: a mechanism by which the information encoded in the DNA is converted into a
complementary RNA copy (information of one nucleic acid is transferred to another; going from
DNA to messenger RNA (mRNA))
For the section of DNA, you will be trying to create a RNA (mRNA) this is so that the
information is able to leave the nucleus in the form of RNA
RNA polymerase (enzyme that assembles the nucleotides into an RNA strand) creates
an RNA sequence that is complementary to the DNA template strand (however, in RNA,
thymine is replaced with Uracil)
RNA polymerase will read the DNA teplate stad 3 to 5 ad eate the
complementary RNA strand that MATCHES the sequence of the non-template DNA
stad 5 to 3
The mRNA molecule serves as a template for protein synthesis
Now this new mRNA can leave the nucleus, attach to a ribosome and that RNA code can
then be used to code for proteins via translation
Translation: it uses the information that is encoded in the RNA to make amino acids into a
polypeptide (information of nucleotides is converted into amino acids)
o The ribosome moves along the mRNA and for every 3 bases of the RNA codes
for a specific amino acid (UAC 3 bases and that is called a CODON); you have
64 possible codons
o 3 letter sequence of RNA nucleotide is designated an amino acid which leads to
the creation of a polypeptide
In prokaryotes, cells can transcribe [immediately available] and translate a given gene
simultaneously but in eukaryotes, the cells transcribe and the mRNA needs to be processed in
the nucleus first before it can go to the cytoplasm and attach to ribosomes for translation
Genetic Code: the nucleotide information that specifies the amino acid sequence of a
polypeptide (the code uses 3 letter words, so the potential is 64 codons but there are only 20
amino acids DEGENERACY)
θ There is a start codon (AUG methionine) it helps identify the starting place because
there is ONLY ONE CORRECT reading frame for each mRNA
θ There are also stop codons that identify the end of polypeptide-encoding sequence and
that new polypeptide chain is released from the ribosome
θ This code is UNIVERSAL this indicates that it was established very early in the
evolution of life and has remained virtually unchanged through billions of years of
evolutionary history (same codons specify the same amino acids in all living organisms)
The ribosome moves along the mRNA and for every 3 bases of the RNA codes for a specific
amino acid (UAC 3 bases and that is called a CODON)
mRNA binds to the ribosome which would cause tRNA (which are linked to an amino acid) to
bind to the ribosome; the tRNA are a special case of RNA molecules that bring amino acids to
the ribosome for assembly into the polypeptide chain
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