Chapter 9
Animations
ESP
Study Guide
Part 3: The Continuity of Life
Mitosis
Review
DNA is made of
molecules
which are composed of
.
The physical
structure
of DNA is a double
: two
strands of
twisted
around
each other.
DNA
involves these steps:
The
enzyme
unwinds the double helix, and
lays down an RNA
.
DNA
adds
nucleotides
to each
strand.
DNA
joins the fragments
together.
DNA replication summary.
The cellular flow of genetic information can be summarized as the
central
: information encoded in
is converted into
in two steps: transcription and translation, resulting in the
of a gene.
Transcription takes place in the
.
RNA
binds to a region on the DNA called the
to assemble a
RNA transcript which contains coding regions called
and noncoding regions called
.
The
exons
are
together to form mature
RNA (mRNA) which exits the nucleus.
Sequences of 3 nucleotides on the mRNA serve as
to translate the genetic code into sequences of
acids, using a
genetic
.
Translation takes place in the
on
.
The ribosome binds mRNA; in turn a
RNA
(tRNA), whose
is complementary to the
on the mRNA, binds to the complex.
The tRNA moves from the
site to the
site and exits at the
site,
adding
a specific amino acid to the growing
chain, until a
codon on the mRNA is reached.
Translation summary.
Gene expression can be turned on or off by regulating access to the
, which controls a cluster of genes that are transcribed together as a unit called an
, as shown in the prokaryotic
lac
operon.
A
mutation
is a change in the
, due to errors in DNA
or to damage from physical or chemical agents called
.
Mutations
that change a single base pair are called
mutations, while insertions and deletions can lead to
mutations.
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Aug 3, 2009
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