Transcription -Translation

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DNA Transcription and Translation
HS-LS3-1. Ask questions to clarify relationships about the role of DNA
and chromosomes in coding the instructions for characteristic traits
passed from parents to offspring.
The students will be able identify and describe the processes of
translation and transcription
Warm up Check
Watch the video and answer the following questions
https://www.youtube.com/watch?v=2zAGAmTkZNY&t=198s
https://www.youtube.com/watch?v=2zAGAmTkZNY&t=198s
1- What are the two processes that are involved in the formation of Protein?
2- Where in the cell does each process happen ?
Task1
Read the given passage and answer the following questions
1-Define transcription
2-What is stated in the central dogma?
3-What are the three main types of RNA? Which is translated into a protein?
Task2
Read the given passage and answer the following questions
Define translation
What is a codon?
What role does tRNA play in translation?
What forms the bond between neighboring amino acids?
Task3
https://www.youtube.com/watch?v=2zAGAmTkZNY&t=198s
https://www.youtube.com/watch?v=WvZ1PK8Uxao
Refer to the link and answer the following questions
List the types and function of the three types of RNA
Summarize the process of translation and transcription
Soon after his discovery of DNA structure, Francis Crick defined the central dogma of
molecular biology, which states that information flows in one direction, from DNA to
RNA to proteins.
The central dogma involves three processes
. • Replication, as you just learned, copies DNA
• Transcription converts a DNA message into an intermediate molecule, called RNA
Translation interprets an RNA message into a string of amino acids, called a
polypeptide.
-
In prokaryotic cells, replication, transcription, and translation all occur in the cytoplasm
at approximately the same time.
In eukaryotic cells, these processes are separated both in location and time. Replication
and transcription occur in the nucleus, whereas translation occurs in the cytoplasm
Types of RNA
Definition: Transcription
Transcription
Nucleus
Location
DNA
Template
(What is read)
To change DNA into a form that
can make a protein
Purpose
Messenger RNA
(mRNA)
Outcome
(End result)
Definition: Translation
Translation
Location
Cytoplasm (by ribosome)
Template
(What is read)
mRNA
Purpose
Amino acids assembled in particular
order to make a protein
Outcome
(End result)
Protein (polypeptide)
(Amino acid)
Start and Stop Codons
Start Codon:
 Begins translation

AUG (universal start codon)


ALSO Codes for methionine(amino acid) (Met)
Sometimes GUG or UUG
Stop Codon:
 Ends translation

UGA, UAA, UAG
Transcription(To copy) occurs in 3 steps
Initiation:
 RNA polymerase binds to DNA at ‘promoter’
 untwists the double helix 10 to 20 bases at a time
Elongation:
 RNA polymerase builds mRNA
DNA:
A
Uses complimentary base pairing
RNA:
Remember: thymine (T) is replaced by uracil (U)
Termination:



RNA polymerase reaches end of gene.
Stops transcribing
Double helix reforms as mRNA molecule peels away.
End Result:

mRNA breaks away from DNA

mRNA exits nucleus
T G C A A
U A C G U U
Translation: ‘new language’
Initiation:
 Ribosome binds at a specific sequence on the mRNA.
 The ribosome moves along the mRNA three nucleotides at a time. This is called a codon.
Each set of three codon) codes for an amino acid.
Elongation:







Ribosome moves along mRNA

From mRNA 5’ end

3 nucleotides of mRNA = codon = amino acid

The “interpreter” tRNA delivers the proper complimentary base to the ribosome.
The anticodon( tRNA) binds by complimentary base pairing to the nucleotides of the codon.
Example: if the codon on a mRNA is UUU, a tRNA with an AAA anticodon will bind to it.
The ribosome links adjacent amino acids with a peptide bond, causing the amino acid to let go of it tRNA.
The finished protein has a sequence of amino acids that have been determined by the mRNA base sequence which has been
translated by the tRNA.
The ribosome then adds each amino acid and the polypeptide chain is elongated.
Elongation occurs until a stop signal occurs.
Termination:

Ribosome reaches stop codon and stops translating
End Result:

Ribosome falls off mRNA and Protein (polypeptide chain) is released
The
Whole
Picture
Next amino
acid to be
added to
polypeptide
Growing
polypeptide
tRNA
mRNA
B. Copying down information in DNA into an mRNA molecule
C. tRNA forming a sequence of amino acids in a protein
d. Anticodons being linked from tRNA in a specific sequence
exit ticket
2. Translation is the process where
A. the code information in mRNA is translated into a sequence of amino acids in a
protein
B. DNA is making a copy of itself
C. Changes are being made to DNA
D. DNA is making RNA
3. What type of molecule being produced is shown below?
A. New DNA
B. mRNA
C. Protein
D. Lipid
4. For the diagram shown on the left,
describe what process is taking place and
where this process takes place inside of the
cell.
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