Chapter8 Gene
Regulation & Mutations
Gene Regulation
• All cells have all the instructions in their DNA to
make all proteins, but they only use the sections
of DNA or genes that they need.
-Promoters are essential to the initiation of
transcription
-Regulatory sites also exist near the promoter
that can regulate transcription
-These proteins can decide whether a gene
gets turned on or off
*Makes gene expression a regulated process
Gene Regulation
• Examples in organisms:
Prokaryotes –
contain operons which are groups of
genes that operate together
-presence of a certain sugar or protein will
activate transcription and the gene will be
expressed
-repressor proteins exist that can inhibit
transcription and turn the gene off
Gene Regulation
Eukaryotes :
- no operons
- utilize a DNA sequence called a TATA box that
helps position RNA polymerase after promoter
sequence
- other enhancer sequences exist to regulate
transcription- wide variety of protein binding can
take place
- DNA binding proteins can still block access to
genes and act like a repressor
Differentiation
Eukaryotic differences:
*Cell specialization requires genetic specialization
- During embryonic development cells differentiate –
meaning they will specialize in structure and function
to an area of the body needed
Hox genes- series of genes that develop in the embryo
and serve master control genes of differentiation
*mutation to a hox gene will completely change
the organs in specific parts of the body
ex: fruit fly with legs on head instead of
antennae
Epigenome
• The epigenome consists of chemical
compounds that modify, or mark, the genome
in a way that tells it what to do, where to do
it, and when to do it.
• Different cells have different epigenetic marks.
• The environment causes changes in our
epigenetics.
http://video.pbs.org/video/1525107473#
Development and
Differentiation
• Similarities exist in the way organisms regulate
genes
*Transcription is the regulating process
which will determine what is turned on and
off
-series of genes work together to shape the
organism (either operons or hox type genes)
-common patterns of genetic control exist
because all these genes descended from one
common ancestor
MuTaTiOnS
• Mutations- changes in the genetic material
- caused by mistakes in copying DNA
- skipped base or incorrect bases can slip
by undetected by the proofreading
polymerase
- can be product of a single gene or a
whole chromosome
Types of Mutations
• Gene Mutations
1. Point mutations
2. Frameshift mutation
• Chromosomal Mutations
1. Deletion
2. Duplication
3. Inversion
4. Translocation
Gene Mutations
• Point mutation – change in one of the base pairs
in the sequence
Ex: substitution of a base will change the
amino acid that is coded
The fat cat ate the wet rat.
The fat cat ate the wee rat.
• What kind of effect would result?
• Overall effect may not even be noticeable or
change anything about the cell
Gene Mutations
• Frameshift mutations - alteration of the
reading frame of the genetic message from
the insertion or deletion of a nucleotide.
Insertion – adds an extra codon or base in
original sequence
The fat cat ate the wee rat.
The fab tca tat eth ewe era t.
• Notice any changes?
Gene Mutations
• Deletions – removes a codon or base from the
sequence
The fat cat ate the wee rat.
The fat cat att hew eer at.
• Where is the change?
• Will these be the same amino acids?
Chromosomal Mutations
• Involves changing the number or structure of
the chromosome
-can change the location of certain genes
and even the number of copies of that
gene
Chromosomal Mutations
• 4 types of mutations:
1. Deletions- involve loss of all or part of
chromosome
2. Duplication – produces extra copies of parts of the
chromosome
3. Inversions – reverses the direction of parts of the
chromosome.
The fat cat ate the wee rat.
The fat tar eew eht eta tac.
4. Translocation – part of one chromosome breaks
off and attaches to another.
The fat cat ate the wee rat.
e the wee rat.The fat cat at
Overall Result
• Mutation will improperly group codons
downstream
• unless at the end, will likely produce a
nonfunctional protein
• it may be transmitted to offspring and to
future generations
• If adversity is great enough to effect the
phenotype of organism it is referred to as a
genetic disorder