Download Transcription Translation Notes

What do we know about DNA?
Where is DNA located in the cell? Nucleus
What does DNA stand for? Deoxyribonucleic acid
DNA is a polymer. What is DNA made of?
Nucleotides = monomers
Function: Stores genetic information = CODE
Nucleotide:
Hydrogen
bonds
• Deoxyribose sugar
• Phosphate group
• Nitrogenous base
(A, T, C or G)
What do we know about RNA ?
What does RNA stand for?
Ribonucleic acid
What is the name of RNA sugar?
Ribose
RNA has Uracil instead of Thymine.
How many strands does RNA have?
One
mRNA, rRNA, tRNA
The three main types of RNA
mRNA carries coded instructions for protein synthesis
from nucleus to ribosomes
rRNA – ribosome (site of protein synthesis)
tRNA – carries specific amino acids to ribosomes during
protein assembly
What do we know about proteins ?
What are proteins made of? Amino acids?
What are some examples of proteins?
Enzymes, antibodies, hemoglobin, hormones,
muscles.
What do we know about the genetic
code (for a protein)
There are four DNA bases:
Adenine, Thymine, Cytosine, Guanine
The DNA bases complimentary to each other:
A-T & C-G
Three nitrogenous bases code for one amino acid
(triplet = codon, or a 3-base code)
Gene is a section of DNA that codes for a specific
protein (sequence of amino acids).
Each codon is made up of 3 letters and
there are 4 possible letters:
How many codons are possible?
4 x 4 x 4 = 43 = 64 possible combinations of codons
- Only 20 amino acids are found in proteins
Possibilities:
- 44 codons (64 – 20) do not code for any amino acid
(wasteful)
More than 1 codon can code for
the same amino acid
Universal Genetic Code
Learning Check
What does the sequence of nitrogenous bases
code for?
Sequence of amino acids in protein (polypeptide).
What is genetic code based on?
Codons (triplet bases)
What is a gene?
A segment of DNA - a code for making a protein.
Code Breaker
Decode the message hidden in the words
Clue: CAPITAL
Life Overcomes Nothing Greater Than Itself
Minus Everything. Now Only Seems Extremely
Easy. Jumping Under Something Terrible, Another
Quirkily Useless Idiot Crafted Knives. Verify it
Stayed In There To Hurt Openly Unique Goat
Herders.
The Central Dogma
TRANSCRIPTION
Nucleus
TRANSLATION
Ribosome
(cytoplasm)
Transcription
DNA  mRNA
gene is copied into mRNA
A section of DNA (_____)
1. An enzyme unwinds and unzips DNA (breaks
it’s ___________
hydrogen bonds) on the section to be
transcribed.
Transcription
DNA  mRNA
2. An enzyme, RNA polymerase, READs the DNA by
adding new RNA nucleotides (A; U; C; G) to the
_______________
complimentary DNA bases on the DNA template
strand.
Ex. DNA triplet: TTC GGC ATT
AUG CCG UAA
mRNA:
Transcription
DNA  mRNA
3. Hydrogen bonds holding mRNA strand to DNA
are broken.
retwists
double helix
4. DNA __________
into its ______________.
Transcription
DNA  mRNA
5. mRNA splicing – before it leaves the nucleus:
 Introns - noncoding regions (“junk”)
 Exons – coding regions (will be expressed)
Transcription
DNA  mRNA
6. Transcription is complete.
7. Mature mRNA leaves the nucleus through a
nuclear pore and travels to the __________
ribosome in the
cytoplasm
Learning Check
Where in the cell does transcription take place?
Nucleus
What is the purpose of transcription?
Make a copy of the DNA message (instructions)
for synthesizing a protein.
What is the product of transcription?
mRNA
Why does DNA need a messenger?
DNA never leaves the nucleus (too big to exit)
TRANSLATION
mRNA  Protein
Process of READING the ________________and
mRNA Codons
translating them into the language of
______________
AMINO ACIDS (protein).
TRANSLATION
mRNA  Protein
Process of READING the ________________and
mRNA Codons
translating them into the language of
______________
AMINO ACIDS (protein).
TRANSLATION
mRNA  Protein
1. mRNA brings genetic sequence (instructions) to
ribosome
the ____________
(rRNA) in the cytoplasm to
make a _____________.
protein
AMINO ACIDS
TRANSLATION
mRNA  Protein
2. The rRNA (ribosome) decodes the copy of the
DNA code carried by the mRNA in 3 letter chunks
called a codon:
|**AUG| CCG|UAA|
Translation begins with a ***AUG - START codon
(Methionine)
TRANSLATION
3. Each codon (3 bases) on mRNA corresponds to a
specific Amino Acid (AA). There are 20 different AA.
TRANSLATION
4. Transfer RNA (tRNA) picks up a floating AA in the
cytoplasm and brings it to the ribosome.
5. Here tRNA anticodon meets the mRNA codon to
align according to the rules A-U; C-G.
6. Once aligned, tRNA drops its AA off and leaves the
ribosome. Another tRNA brings the next AA.
TRANSLATION
7. Peptide bonds form between amino acids
Protein Sequence = Order of the amino acids
TRANSLATION
Translation termination
8. Process repeats. Translation continues until it hits a
STOP codon (Ex. UAA) and the polypeptide (protein) is
released.
STOP codons: UAA, UAG or UGA
Learning Check
Where in the cell does translation take place?
Cytoplasm on the ribosome
What is the purpose of translation?
Translate the language of mRNA codons (bases)
to the language of amino acids (protein).
What is the product of translation?
Protein (polypeptide)
An overview of protein secretion in eukaryotic cells:
Most protein gets transferred from a RIBOSOME on the
ROUGH ER to the Golgi apparatus.
Ribosome
Step 1: Protein (polypeptide) is transported to the ER.
Modification of a protein begins here.
Step 2: Transport vesicle
Step 3: Intra-
take proteins to the Golgi
apparatus
Golgi vesicle
transport
Step 4: Proteins that will leave
the cell are packaged in
secretory vesicles. Proteins
that remain in the cell are
packaged in lysosomes
(digestive enzymes) or storage
vesicles.
Universal Genetic Code