Download DNA lecture Notes

Genetics
The Importance of DNA
The Genetic Code
• What is DNA exactly?
– It’s a chemical code made up of many molecules
• aka macromolecule (nucleic acid)
– All inherited instructions of life are contained in
these molecules
DNA
• DNA needs to store info
to be passed on from
generation to generation
• It needs to be able to
copy itself
• It must be strong and
stable
• It must be able to mutate
or change slightly from
time to time
– Why do you think?
DNA
• If testing your DNA
could predict your
potential for contracting
a serious disease, would
you do it?
– Why?
– Why not?
DNA Structure
• DNA is made of
billions of subunits
called nucleotides.
• Each subunit has 3
parts;
– Sugar
– Phosphate
– One of 4 bases (A, T,
C, G).
Describe the arrangement of
molecules in this close-up
view of DNA.
DNA Structure (2)
• Because DNA is
double strand,
subunits are paired.
• Chemically, A bonds
only with T and C
only with G.
• This will help explain
how it copies itself
Why does adenine only bond
with thymine? Cytosine with
guanine?
DNA Structure (2)
• Fill in the blanks
DNA
• How does our body
make use of the genetic
info stored in DNA?
– They need to change that
information into proteins,
which are made up of
amino acids
– This is all dependent on
the sequence of DNA
subunits
• So how does this all
happen?
DNA Replication
• If weak chemical bonds hold the base pairs
together, then the DNA can also separate at those
bonds as well
• The base pairs split apart when DNA is copied,
making two templates.
DNA Replication
• Free-floating subunits bind with each
exposed end, resulting in two identical
pieces of DNA.
– Why would DNA need to create
an identical copy of itself?
What is happening in this
picture? What do you think
the ending “-ase” mean?
DNA Replication
Replication Problems
• A mutation occurs
when there is a
RANDOM change to
the DNA sequence .
• Most mutations are
repaired; of the rest,
most have no effect,
many are harmful,
but a rare few are
helpful.
Are these mutations good, bad,
or neither? What is the
importance of mutations in
regard to species survival?
Mutation Types
• Substitution =
changing one or
more bases
• Deletion/addition =
losing or gaining
bases
• Inversion = flipping
over a segment of
bases
BRCA 1 & 2 Video
Mutation Animation Video
Effects of Mutations
• Some mutations
change an organism’s
survival advantage,
possibly leading to
new species.
• Other mutations result
in different ways that
DNA instructions are
carried out.
A random mutation gives people another
way to make RBC, leading to resistance to
malaria. What happened to the
incidence of this gene?
Cancer as a Mutation
Proteins Review
• Carries out the work of a cell
– They build materials, transport substances, send
signals, provide defense, and control metabolic
activities
• Molecules formed as long chains
• Formed from various combinations of 20 kinds
of amino acids
– Arranged in a specific sequence (order)
20 Amino Acids
Proteins Review
• Amino acid (a.a.)
sequence determines
protein shape
– Bends or folds a certain
way based on what binds
to what within the chain
• Final folded shape
allows for protein to
carry out its function in
the cell
Proteins Review
• Many proteins made by
cells become enzymes
– Remember, they were
those things that ended
in “ase”
– What do they do again?
Protein Synthesis
Protein Synthesis
• DNA, found in the
nucleus, has
instructions for how
to make protein.
DNA
RNA
Protein Synthesis (1)
• The instructions are copied onto a
messenger–RNA – before entering the
cytoplasm (watery fluid inside cell).
Transcription
• The process by
which DNA is copied
into mRNA
Figure 17.3b-1
Nuclear
envelope
TRANSCRIPTION
DNA
Pre-mRNA
(b) Eukaryotic cell
Figure 17.3b-2
Nuclear
envelope
TRANSCRIPTION
RNA PROCESSING
mRNA
(b) Eukaryotic cell
DNA
Pre-mRNA
Protein Synthesis (2)
• The mRNA attaches to a ribosome in the
cytoplasm and attracts transfer- RNA.
Protein Synthesis (3)
• tRNA anticodon binds to mRNA at the codon
Figure 17.UN04
Polypeptide
Amino
acid
tRNA
E
A
Anticodon
Codon
Ribosome
mRNA
Protein Synthesis (3)
• Each piece of tRNA
brings one amino acid
to the ribosome.
Translation
• The process of
assembling amino acid
chains from information
in mRNA
Figure 17.3b-3
Nuclear
envelope
TRANSCRIPTION
RNA PROCESSING
DNA
Pre-mRNA
mRNA
TRANSLATION
Ribosome
Polypeptide
(b) Eukaryotic cell
Protein Synthesis (4)
• Each amino acid is
attached in the
sequence as called for
by the mRNA.
• A long chain of amino
acids makes up a
protein.
Figure 17.3b-1
Nuclear
envelope
Let’s
Review
the
Process
TRANSCRIPTION
DNA
Pre-mRNA
(b) Eukaryotic cell
Figure 17.3b-2
Nuclear
envelope
TRANSCRIPTION
RNA PROCESSING
mRNA
(b) Eukaryotic cell
DNA
Pre-mRNA
Figure 17.3b-3
Nuclear
envelope
TRANSCRIPTION
RNA PROCESSING
DNA
Pre-mRNA
mRNA
TRANSLATION
Ribosome
Polypeptide
(b) Eukaryotic cell
Figure 17.4
DNA
template
strand
5
3
A C C
A A
A C
T
T
T
G G
T
C G A G
G G C
T
T
C A
3
5
DNA
molecule
Gene 1
TRANSCRIPTION
Gene 2
U G G
mRNA
U U
U G G C U
C A
5
3
Codon
TRANSLATION
Protein
Trp
Phe
Gly
Ser
Gene 3
Amino acid
The Importance of Protein
• Most body parts are
made of protein
(“structures”).
• Most enzymes are
proteins (control of
bodily reactions).
If our body can create
proteins, why do we
need to eat them?
Food
Amount of
protein (grams)
Spirulina, 1 cup
64
Tempeh, 1 cup
41
Dried Parsley, 1 cup
31
Lentils, cooked 1 cup
18
Black Beans, cooked 1 cup
15
Tofu, 3.4 oz
20
Quinoa, cooked 1 cup
9
Peanut Butter, 2 tbsp
8
Almonds,1/4 cup
8
Sun-dried Tomato, 1 cup
8
Brown Rice, cooked 1 cup
5
Broccoli, cooked 1 cup
4
Potato, 1 med.
4
Lambs quarters, 1 cup
4