Gene Regulation & Mutations
Vocabulary Terms
Gene regulation
Operon
Promoter
Operator
Gene
Transcription Factor
Mutagen
Mutation
Point Mutation
Substitution
Missense
Nonsense
Frameshift
Deletion
Insertion
First:
Regulating Genes
An operon is a segment of DNA that has a
promoter, an operator, structural genes, and
regulatory genes.
Structural genes are genes that code for
polypeptides that are needed for various cellular
functions.
Regulatory genes are genes that code for
polypeptides that “regulate” structural genes.
Gene Turned On
•The promoter is the section of DNA where the
RNA polymerase binds to start transcription.
•It “promotes” (or encourages) the attachment
of RNA polymerase to the DNA.
Gene Turned Off
•The operator section of DNA is like the “on/off switch” for
the gene.
•When the operator has a repressor protein attached to it,
the RNA polymerase is blocked from starting transcription.
•Without transcription, translation and protein synthesis
cannot take place.
Transcription factors are proteins that regulate
transcription.
•Help RNA polymerase bind to the promoter (“general”
transcription factor).
•Block RNA polymerase from binding to the promoter
(repressor protein).
•Speed up the rate of transcription (activator protein).
Second:
Mutations
•A mistake in the DNA replication process
(mismatched base pairs) that results in a change to
the DNA is called a mutation.
•Mutagens are chemicals or radiation that cause
mutations.
A point mutation is a change in a single nucleotide
in a gene.
•Exchanging a nucleotide for a different one is a
substitution mutation.
•Removing (deletion) or adding (insertion) a
nucleotide causes a frameshift mutation.
Keep in mind the
central dogma of
biology:
DNA>RNA>Protein
Point mutations
change DNA.
The altered DNA
creates a different
mRNA transcript.
The altered
mRNA codes for
a different
amino acid.
A polypeptide
chain with an
altered amino
acid sequence
will be created.
The deformed
protein might
not work
properly.
Point Mutation
Normal
Substitution
(Missense)
Substitution
(Nonsense)
Fake Gene
RED FOX HAS SOX
RED FOX HHS SOX
RED SOX
“F” replaced with
“S” (creating a stop codon)
RED FOX HSS OX
“A” removed
RED FOX HAT SSO X
“T” added
“early termination”
Frameshift
(Deletion)
Frameshift
(Insertion)
Change
none
“A” replaced with
“H”
Point Mutation
mRNA Sequence
Normal
Substitution
(Missense)
Substitution
(Nonsense)
AUG UAC GAU UAA
AUG UAC GGU UAA
AUG UAG GAU UAA
“early termination”
Frameshift
(Deletion)
Frameshift
(Insertion)
AUG UAC AUU AA
AUG GUA CGA UUA
Amino Acid
Sequence