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Protein Synthesis
Chapter 10
RNA
• ribonucleic acid
• contains the sugar ribose, uses uracil
instead of thymine
• is single stranded
• usually much shorter in length than DNA
(about the length of one gene)
RNA & Transcription
During transcription,
RNA polymerase
binds to DNA and
separates the DNA
strands.
RNA polymerase then
uses one strand of
DNA as a template
from which
nucleotides are
assembled.
RNA vs. DNA
RNA
• Single-stranded
molecule in most of its
biological roles and has
a much shorter chain of
nucleotides.
• Contains ribose
• Complementary
nucleotide to adenine is
uracil
DNA
• Double-stranded helix
• Contains deoxyribose
• Complementary
nucleotide to adenine is
thymine
So why the
big diff?
How Genes Work
• Genes are coded DNA
instructions that control
the production of proteins
with in the cell.
• The first thing that needs
to happen is for DNA to
be copied into RNA.
(transcription)
• Now the RNA contains
the coded information for
making proteins.
The many faces of RNA
• Messenger RNA (mRNA): carries
copies of instructions for assemble of
amino acids into proteins from DNA to
the rest of the cell
• Ribosomal RNA (rRNA): makes up the
major part of the ribosome
• Transfer RNA (tRNA): transfers amino
acids to ribosomes during protein
synthesis
Vocab!! Yes!!
The Genetic Code
• mRNA has a “4”
letter alphabet: A,
U, C, G
• “words” (codes) are
only 3 letters long
• each 3 letter “word”
is called a codon
The Genetic Code
• Start codon: AUG
– mRNA: indicates where translation should
begin
• Stop codons: UAA, UAG, UGA
– Signal for translation to end
The Genetic Code
UCGCACGGU
UCG-CAC-GGU
Serine-Histidine-Glycine
Translation
Definitely
a
definition.
• Decoding of a mRNA message into a
polypeptide chain (amino acids)
• Takes place on the ribosomes.
DNA replication
RNA transcription
polypeptide
mRNA translation
Translation
• mRNA has the codon
• tRNA has the anticodon
Summary