Bio1151b
Chapter
17
From Gene to Protein
A major function of DNA is to direct the
synthesis
of
in two
steps:
and
.
In prokaryotes, transcription and translation take place
simultaneously.
In eukaryotes, an intermediate
step
of RNA
is needed due to the
presence
of the
.
Transcription
has three stages:
initiation,
elongation.
and
termination.
In eukaryotes, the "pre-mRNA" requires modification before it can be used in
translation.
The 5
'
end receives a modified nucleotide
, and the 3
'
end gets a
tail.
are removed from the
pre-mRNA
and its
are
spliced
together.
The mRNA exits the nucleus, and translation takes
place
on
.
The genetic information on mRNA is encoded as a sequence of RNA
triplets,
or
. The
possible codons constitute the genetic
code.
The
RNA
(tRNA)
binds with the mRNA
to add a specific amino acid to the polypeptide chain through
bonds.
Translation
also has three stages:
initiation,
elongation,
and
termination.
Summary.
Review.
are changes in the DNA of a cell which may lead to an abnormal
.
mutations
are changes in one base pair of a gene.
A
base-pair
mutation changes one pair of nucleotides.
Insertions and deletions of nucleotide pairs may produce
mutations.