Transcript DNAppt

DNA
Deoxyribonucleic Acid
The blueprint of the cell
Building Blocks of Life Recap:
• Quarks and Leptons which make up
• Atoms which make up
• Molecules
– DNA and RNA Bases are Molecules
– 3 bases make a Codons, each codon codes
for a specific Amino Acid
– Amino Acids link to form proteins
Quarks and Leptons
• Proton: 2 up quarks + 1 down quark
– +2/3 +2/3 -1/3 = +3/3 or +1 charge
• Neutron: 2 down quarks + 1 up quark
– -1/3 -1/3 + 2/3 = 0/3 = 0 charge
• Electron: 1 electron lepton, -1 charge
Atom
- 3 types of subatomic particles
- Each element has a specific number of protons
Artistic representation of DNA Base Molecules
Key is
C = Carbon atom
N = Nitrogen
O = Oxygen
H = Hydrogen
Base Pairing
Artistic representation of DNA
molecules
(Adenine, Guanine, Cytosine, Thymine)
• milkywaytoquarks
Historical Background
• In 1952, Rosalind Franklin used an x-ray
method to photograph DNA molecules
James Watson
and Francis
Crick used
Rosalind’s
photographs
to figure out
the doublehelical
structure of
DNA in 1953
Structure of DNA
DNA is shaped like a twisted ladder.
This shape is called a double helix.
• The sides of the helix are made of
sugars and phosphates
• The “rungs” are paired chemical
structures called “bases”
DNA has four bases
1: Adenine
2: Thymine
3: Guanine
4:Cytosine
Adenine always bonds with
Thymine, and Guanine always
bonds with Cytosine.
The bases fit together
like puzzle pieces
Imagine you have a
piece of DNA, and
you cut it down the
middle. You would
be left with two
strands.
If we have one strand
or side of a DNA
sequence, we can
tell what the other
side is. It works just
like a code.
If you had this half, you would look
at the bases (T stands for Thymine,
A for Adenine, C for Cytosine, and
G for Guanine), and then think of
which bases pair with them.
• Thymine bonds with Adenine, Adenine with
Thymine, Cytosine with Guanine, etc…
Each section of DNA on a chromosome is called
a gene. (p 130) Each gene directs the making of
a specific protein. Genes are responsible for
what you look like, for example, it determines
your eye and hair color, and how tall you are,
what shape your nose is, etc…
Groups of three bases are called codons.
Each codon stands for an amino acid.
Amino acids make up proteins, which are
necessary for building and repairing body
tissues.
3 bases = codon
each codon is the instructions for an amino acid
• Primary Structure:
order of amino
acids
• Tertiary Structure:
3-D structure of
protein (the way the
amino acids roll up
together, like a wad
of string)
RNA
• Before protein synthesis can take place, a
“messenger” must first carry the genetic
code from the DNA inside the nucleus into
the cytoplasm. This genetic messenger is
called RNA, which stands for ribonucleic
acid. RNA is a lot like DNA, but is has one
strand instead of two. It also has a
different base, called Uracil, in the place of
the base Thymine.
There are several types of RNA
• Messenger RNA (mRNA) – copies the
coded message from the DNA in the
nucleus, and carries the message to the
ribosome in the cytoplasm.
• Transfer RNA (tRNA) carries amino acids
to the ribosome and adds them to the
growing protein.
Replication Process
during the
Replication Process
DNA’s double helix
unzips into 2 strands.
Each strand’s bases
are paired with new
complimentary bases
forming 2 identical
strands of DNA, each
half old and half new.
transcription
Sometimes mistakes are made
during replication, for example, an
base might be substituted for a
wrong base. Or part of the strand
might be duplicated or deleted.
• These mistakes are called mutations. Mutations are
unimportant or bad, causing children or animal babies to
be born with extra fingers, albinism, problems with sight,
deformities of the heart, cleft palate, muscular dystrophy,
color blindness, etc…
Review of DNA and transcription
1. Refer to page 133. Raise your hand if you
think that the strand on the top is RNA.
Raise your hand if it is DNA.
DNA
CCT-GAT-TAC
2. What are the complimentary
bases?
GGA-CTA-ATG
3. What happens if there is a
mistake made when the DNA is
copied?
mutation
4. What are the rungs on the DNA
ladder called?
Bases
What are some differences
between DNA and RNA?
DNA has two strands and the base Thymine
RNA has one strand and the base Uracil
Sections of DNA on the
chromosome responsible for
different physical characteristics
are called …
Genes (not to be
confused with
jeans)
How many bases in a codon?
• Three
Extra Material
• DNA video Bill Nye