D.N.A.
DeoxyriboNucleic Acid
A molecule that contains our
genetic information
Is found in the nucleus of almost
all cells wound up into
chromosomes.
DeoxyriboNucleic Acid
Double Helix (Twisted Ladder)
Watson and Crick
Double stranded
Made of Nucleotides: Sugar,
Phosphate, Base
Has 4 nitrogen bases: Adenine,
Guanine, Thymine, Cytosine
Combination of these bases (order)
is what makes up our traits
Nucleotides
What are the 3 parts to a
nucleotide?
Base Pair
Base Pair
Complete the DNA strand
TACGCCCGTTATCATA
A??????? ??? ?? ???? Hydrogen
Bonds!!!
Purines (Adenine, Guanine)
double ring
Pyrimidines (Thymine, Cytosine)
single ring
Replication
Why Replicate (copy)?
STEPS TO COPY DNA:
1. DNA UNWINDS
2. DNA UNZIPS
3. BASE PAIRS ARE ADDED TO BOTH STRANDS
4. 2 NEW DNA MOLECULES
Replication
DNA Polymerase – adds new bases
Helicase – unzips (breaks hydrogen bonds) DNA
DNA molecule
http://www.dnai.org/index.html
Base Pairing
http://gslc.genetics.utah.edu/units/basics/
Replication
http://www.pbs.org/wgbh/aso/tryit/dna/index-nojs.html
RNA
Ribonucleic acid
RNA is a messenger for DNA.
RNA takes the genetic information from
DNA and takes it to the ribosomes
where it makes the proteins
3 differences between
RNA and DNA
1. RNA = ribose (does
have oxygen)
DNA – deoxyribose
(does not have oxygen)
2. RNA has a single strand
DNA has a double
strand
3. RNA has uracil as a
base instead of
Thymine like DNA has
RNA
3 types
messenger RNA – takes info from
nucleus to ribosome
transfer RNA – transfers amino acids to
ribosome to make proteins
Ribosomal RNA – makes up ribosomes
RNA
Protein Synthesis
http://www.pbs.org/wgbh/aso/tryit/dna
/index-nojs.html
Protein synthesis is
transferring the
information that
DNA gives to mRNA.
mRNA transfers that
information to
ribosomes
Why ribosomes?
Because ribosomes makes
proteins which is the
foundation for all cells.
Yo! Ribo!
Once the mRNA
leaves the nucleus,
it travels in the cell
looking for a
ribosome
When the mRNA
finds the ribosome,
the ribosome binds
onto the mRNA
ribosomal-RNA
Notice the split in the
ribosomes – there is a
small part and a large
part. Each of those two
parts is called a
'subunit' and is made
up of many proteins
and RNAs.
It's a special RNA made
expressly for the
purpose of using in
ribosomes, called
'ribosomal-RNA‘ or
rRNA.
Let's watch them make a protein, then we'll
see the secret code and how it works.
The ribosome crawls
along messenger-RNA
and translates the
genetic code into
which amino acid
belongs where.
Then it super glues the
amino acids together.
The chain of super
glued amino acids is
called a protein.
ONS The ribosome only looks
at three nucleotides in
a row.
These three
nucleotides are the
code. They are like
three letter words. In
English, 'dog' and 'cat'
and 'you' are three-
letter words that mean
different things.
Those scientists call a
three-nucleotide 'word'
a 'codon'.
Looky! Code is part of
the word codon.
Lets make our own message
using three-letter words
If we made this chain,
someone would read
the message and tell
each person or animal
where to get in line.
As each one got in the
right order, the reader
would tell them to hold
hands, or paws, to keep
them in the right order.
“The Code”
The ribosome does
it slightly differently.
The ribosome needs
help with the
reading part. It gets
that help from its
cousins, the
transfer-RNAs.
The transfer-RNA
The transfer-RNAs, help
the ribosome read the
three letter 'words' by
having three
nucleotides exposed on
their bottoms.
These three nucleotides
are called an anti-
codon.
anti-codon because
they fit exactly, like a
puzzle piece, with my
three-letter 'words'
called codon.
So, that's really all there is to the
genetic (secret) code
The secret is that
messenger-RNA is
really a string of
three-letter 'words'
that tell the
ribosome what the
correct order of the
amino acids are in a
protein
Here's the whole crew, doing their
thing! Watch what happens!
The transfer-RNA floats
in and if its anti-codon
matches up with
mRNA’s codon, it gives
up the amino acid it
was carrying. Then the
ribosome super glues
the new amino acid to
the end of the amino
acid chain it has been
growing.