Section 3:
What is a
gene?
Genes
First let’s compare
Chromosomes to a towel
Chromosome
Chromatin = Long
strands of DNA
Chromosome : coiled up
strand of chromatin
The “X” shape is where
the chromosome has
been copied.
Chromatin
Chromosome
How many chromosomes do
we have in our nucleus?
How many chromosomes do
we have in our nucleus of
each of our cells?
a.
b.
c.
d.
23
52
108
46
What is a Gene?
 Gene: functional unit that controls
inherited trait expression that is
passed on from one generation to
another generation.
Genes
 In other words, Genes are pieces of our DNA that
code for our traits.
Proteins from Genes
• Gene: Part of chromosome that
codes for a protein
The Human Genome
• How many paired nucleotides do
we have? (i.e. how many base
pairs do we have?)
In 1964, Friedrich Vogel
estimated that the total number
of genes in the human genome
to be ~ 6.7 million
Trait
What is a Trait?
Trait = Any characteristic
Inherited Trait
Inherited trait = a characteristic that you
get from your biological parents
and….
• a trait you are born with.
• It’s in your DNA!
• What are some examples?
EX: (Write down one of your inherited
traits)
Acquired Trait
Acquired trait = a characteristic that you
develop in your lifetime
• a trait you learn or pickup after you
are born (not inherited from your
parents) like you lost an arm, you got
a tattoo, you learned a skill like piano
• What are some examples?
EX: (Write down one of your acquired
traits)
Section 5:
Mutations
Mutations
Evr made a mitsake
in yourr spelng?
MUTATIONS!
A mess up in the DNA
sequence
Where do mutations occur?
IN THE DNA!!
(not the RNA)
When do mutations occur?
During replication
MUTATIONS!
Gene Mutations (2 types):
Changes in a single base
Chromosomal Mutations (4 types):
Changes in whole chromosomes
Gene Mutations,
there are two
types:
Point Mutations
Frameshift Mutations
Point Mutation
A T G AA T A G C T G G A G G G A T T T T
TACTTATCGTCCTCCCTAAAA
Think about what would happen if the nitrogen
bases paired incorrectly.
How are proteins made? If you try and make a
protein when you have an incorrect nitrogen
base you will end up with the protein in the end.
Point Mutation
A T G AA T A G C T G G A G G G A T T T T
A UG A A U A G C A G G A G G GA U U UU
TACTTATCGTCCTCCCTAAAA
This is showing the bottom DNA strand, with
the wrong nitrogen base, being transcribed
into an mRNA strand. Because the T was in
the DNA strand, we now have an A instead of a
U in our mRNA strand. What will that do to the
sequence of amino acids?
Point Mutation
These happen at only ONE POINT or base
Usually
oneamino
base
is does
replaced
by a different
What
acid
the AGG
base codon code for??
What amino acid does the UGG
End result:
codon code for??
Are theyacid
the same
amino
acid? chain is
ONE amino
in the
protein
wrong
MET
ASP
SER
ARG
ARG
ASP
A
PHE
A UG A A U A G C A G G A G G GA U U UU
Point Mutation
These happen at only ONE POINT or base
Usually one base is replaced by a different
base
End result:
ONE amino acid in the protein chain is
wrong
MET
ASP
SER
ARG
ARG
ASP
A
PHE
A UG A A U A G C A G G A G G GA U U UU
A A Frameshift mutation will
occur when you have a missing
nucleotide.
Frameshift
A T G AA T A G C T G G A G G G A T T T T
TACTTATCGTCCTCCCTAAAA
Frameshift
A T G AA T A G C T G G A G G G A T T T T
A UG A A U A G C A G G A G G GA U U UU
TACTTATCGTCCTCCCTAAAA
The mRNA will be missing a
nucleotide too.
Frameshift
A UG A A U A G GU G G U G G GA U U UU
Frameshift
A UG A A U A G G G G U G G G A U U UU
Frameshift
MET
ASP
SER
TRY
ARG
ASP
A
PHE
A UG A A U A G C U G G A G G GA U U UU
Frameshift
This causes a SHIFT in the rest of the
sequence following the mutation
End result:
Every amino acid after the mutation is
wrong!
MET
ASP
SER
GLY
GLY
ISO
A UG A A U A G C G G A G G GA U U UU
MUTATIONS!
Chromosomal Mutations (4)
Changes in whole chromosomes
Chromosomal Mutations
1. Deletion:
part of the chromosome is lost
Chromosomal Mutations
1. Deletion:
part of the chromosome is lost
2. Duplication:
part of the chromosome is repeated
Chromosomal Mutations
1. Deletion:
part of the chromosome is lost
2. Duplication:
part of the chromosome is repeated
3. Inversion:
part of the chromosome gets reversed
Chromosomal Mutations
1. Deletion:
part of the chromosome is lost
2. Duplication:
part of the chromosome is repeated
3. Inversion:
part of the chromosome gets reversed
4. Translocation:
two chromosomes that are NOT pairs
switch information
What you should be able to
answer for the quiz:
1.
2.
3.
4.
5.
6.
7.
What are the two types of gene mutations?
What are the four types of chromosomal mutations?
What is the difference between a gene mutation and a chromosomal
mutation?
Be able to identify examples of the four types of chromosomal mutations?
Be able to translate an mRNA strand from DNA and be able to code the
amino acid sequence that would result from the mRNA sequence.
Know what a codon is and what an anticodon is.
What is the difference between Transcription and Translation.