Bellwork:
• Place DNA Molecule in the
collection folder.
Describe how the structure
of DNA relates to its
function.
DNA Replication
DNA Replication
•
•
•
•
http://www.youtube.com/watch?v=hfZ8o9D1tus
http://www.youtube.com/watch?v=4jtmOZaIvS0
http://www.johnkyrk.com/DNAreplication.html
http://highered.mcgrawhill.com/sites/0072437316/student_view0/chapter
14/animations.html#
From DNA to Protein
Using the information encoded in
the DNA to:
Producing Proteins!
= “Protein Synthesis”
Why are Proteins Important?
--help build cell organelles (cell
membrane)
--are used as enzymes to promote
reactions
--are found in muscles, blood, skin,
bones, etc.
Figure UN15-5
(information storage)
Transcription
(information carrier)
Translation
(active cell machinery)
Making a protein is like reading a
library book.
Cell
Neighborhood
Nucleus
Library

-----------------------------------------------------------------
---------------------------------
Homework
Making a protein is like reading a
library book.
Cell
Neighborhood
Cytoplasm
Nucleus
Library
?
New
Protein

---------------------------------
Home
?
Homework
Information Flows in One
Direction:
DNA RNA Proteins.
Transcription
(Nucleus)
Translation
(Cytoplasm)
Transcription:
A modified copy of the DNA
A. Keeping the DNA
‘encyclopedia’ safe in the
nucleus.
B. Copying only the necessary
information (‘pages’).
C. Only when the information is
required.
DNA and RNA
Compare DNA to RNA:
Structure
# of Strands:
Sugar:
Bases:
DNA
RNA
2
1
Deoxy- Ribose
Ribose
ACGT ACGU
Thymine Uracil
TRANSCRIPTION
translation
Takes place in the
nucleus
Moves out of nucleus
into the cytoplasm &
attach to ribosome
(information storage)
Transcription
(information carrier)
Translation
(active cell machinery)
RIBONUCLEIC ACID
(RNA)
• HOW IS RNA
DIFFERENT
FROM DNA??
Let’s review DNA
•Contains the sugar
DEOXYRibose
• ADENINE pairs with
Thymine
• GUANINE pairs with
Cytosine
•Double Stranded
RNA is different
from DNA…
•Contains the sugar
Ribose
• Uracil Substitutes for
Thymine (A pairs with U)
•Single Stranded
Fill in Your Chart…
Differences Between DNA and RNA:
DNA
RNA
SUGAR
Deoxyribose
Ribose
NITROGEN
BASES
A, T, C, G
A, Uracil, C, G
SHAPE
Double Helix
Single Strand
• RNA is the same structure as
DNA, it is rearranged in the
complementary order.
DNA = A T T G C A C
RNA = U A A C G U G
How is RNA made?
Through TRANSCRIPTION!
Here’s a Summary:
Transcription: RNA is made from DNA to
use during protein synthesis. Same
process as replication, but only one side
of the DNA strand is copied. This occurs
in the nucleus. When RNA is made it
leaves the nucleus (through pores in the
membrane) and the DNA strand zips back
up.
Why is RNA important?
• It contains the code from
DNA that is needed to
make proteins!
What are proteins?
• Organic Compounds that are made
from amino acids linked together by
covalent, peptide bonds
Ex. AA1 + AA2 + AA3 = a protein/
polypeptide
Why are Proteins Important?
--help build cell organelles (cell
membrane)
--are used as enzymes to
promote reactions
--are found in muscles, blood,
skin, bones, etc.
Three Types of RNA
• Messenger RNA (mRNA) – transcribes the code from
DNA and takes it from the nucleus into the cytoplasm to
the ribosome.
• Transfer RNA(tRNA) – translates the message by
transferring amino acids from the cytoplasm to the
ribosomes to the mRNA.
• Ribosomal RNA (rRNA) – structural component
of ribosome that binds mRNA and tRNA
together; makes up 80% of all RNA in the cell.
Protein
Synthesis –
THE
MAKING OF PROTEINS
2 Processes in Protein Synthesis
• Transcription
• Translation
Transcription
mRNA copies the code
from DNA
TRANSCRIPTION –
the details
Transcription
• Segments of DNA are separated by RNA
polymerase, one of the strands is used as a
template to make the molecule of mRNA
• RNA polymerase adds mRNA nucleotides as it
reads the code and binds them with their
complementary nucleotides on the DNA
LET’S DO TRANSCRIPTION!
DNA = A
mRNA = U
G
C
C
G
T
A
G
C
A
U
TRANSCRIPTION
•The base sequence in mRNA is a code that
enables the tRNA to collect the right amino
acids and assemble them in the correct
sequence to synthesize a protein.
•Codon: Every combination of three
“letters” (nitrogen bases).
• 1 CODON = 1 AMINO ACID = 3 NUCLEOTIDES
what do the codons
code for?
The genetic codethe correspondence between
triplets in DNA and the amino
acids in proteins
Each amino acid is coded for by 3
mRNA bases arranged in a specific
sequence
Translation (tRNA)
• Translates the mRNA bases into amino acids that
will make up a protein.
• Ribosome attaches to the mRNA
• tRNA picks up specific amino acids in the
cytoplasm and carries them to the mRNA at the
ribosomes
•tRNA contains the anticodon
that complements the codon on
the mRNA
TRANSLATION—
The Details
1. mRNA strand (made of codons) leaves
the nucleus, enters cytoplasm,
attaches to ribosome
2. tRNA molecules pick up amino acids in
cytoplasm and carries them to ribosome
3. tRNA anticodon pairs with mRNA codon,
joining the two molecules
4. When 2 amino acids are in place a
polypeptide bond forms
5. Once an amino acid has joined the
chain, the tRNA detaches from the
mRNA strand
6. The process continues until a chain of amino
acids is formed and stops once a stop codon
on the mRNA is reached.
7. The chain of amino acids is called a protein
or polypeptide.
TRANSLATION (tRNA)
• DNA
=A T G
C T
A
• mRNA = U A C G A U
(Codon)
• tRNA = A U G C U A
(Anticodon)
Let’s summArize
Protein synthesis!
TRANSCRIPTION
translation
Takes place in the
nucleus
Moves out of nucleus
into the cytoplasm &
attach to ribosome
SUMMARY: 5 Steps of Protein Synthesis
1. Transcription: DNA makes RNA (in the nucleus)
2. RNA now becomes mRNA which will leave the
nucleus (take the code to ribosome)
3. mRNA tells ribosomes what proteins to make
4. mRNA attaches to ribosome and forms a pattern
(codon) to make a protein
5. tRNA in cytoplasm comes to ribosome. It
“translates” the code (codon=three base pairs) and
goes and gets the specific amino acid that matches
up with the codon. This is the anticodon. When
amino acids are combined together (by covalent,
peptide bonds) they break off and form the
specific protein needed by the cell. This part is
called Translation.
Steps to figure out the genetic code
1. Obtain a DNA Template. (a row of DNA bases)
2. Transcribe DNA into mRNA
3. Translate mRNA into tRNA
4. Use the codons (mRNA) to translate into amino acids
Why do some amino acids have
more than one code?
• 4 nucleotide bases, 3 at a time = 43 = 64
• 20 different amino acids and 64 code
words, so some AA are specified by
more than one code word.
Let’s prActice!
DNA
ATG
mRNA (Codon)
UAC
tRNA Strand
(anticodon)
AUG
Amino Acids
Tyrosine
More practice needed?
DNA= TAC -GAT-GCC-ATC
-CUA- CGG-UAG
mRNA= AUG
________________
tRNA= ________________
UAC -GAU-GCC-AUC
START-LEU-ARG-STOP
Amino Acids= _________________