Download RIBONUCLEIC ACID (RNA) NOTES

RNA and Protein Synthesis NOTES
RNA Structure
HOW IS RNA DIFFERENT FROM DNA?
DNA (Deoxyribonucleic Acid)
o Contains the sugar deoxyribose
o Adenine pairs with thymine
o Guanine pairs with cytosine
o Double stranded
RNA (Ribonucleic acid)
o Contains the sugar ribose
o Uracil substitutes for thymine (A pairs with
U) and G pairs with C
o Single stranded
Differences between DNA and RNA
DNA
RNA
5-carbon sugar
Nitrogen bases
Shape of Molecule
RNA and Protein Synthesis
Define a gene.
Think of DNA as a prisoner inside the nucleus of the cell. DNA can never leave the nucleus as it must stay there to
control all cell functions.
 To make a protein, DNA needs a helper called ______________________________ = RNA, which can enter and
leave the nucleus
Three Types of RNA
1. Messenger RNA (mRNA) –
Remember, amino acids are the monomers of proteins
2. Transfer RNA (tRNA) –
3. Ribosomal RNA (rRNA) –
It makes up 80% of all RNA in the cell.
How is RNA made?
Here’s a Summary:
________________________: RNA is made from _________. Same process as replication, but only _______ side of the
DNA strand is copies. This occurs in the _________________. When RNA is made it leaves the nucleus (through nuclear
pores in the membrane) and the DNA strand zips back up.
Why is RNA Important?
What are Proteins?




Ex. AA1 + AA2 + AA3 = a protein ( also known as a ________________________)
Each polypeptide can have a combination of any or all of the 20 different AA
One protein is different from another by the ____________ in which the different AA are joined together to
produce a polypeptide
Why are Proteins Important?


 are found in muscles, blood (hemoglobin), insulin, antibodies and other body structures (hair, skin, bones,
ligaments, tendons)
Protein Synthesis – the making of proteins
What are the two processes of protein synthesis?
TRANSCRIPTION:
Describe the process of transcription.

So RNA polymerase uses one strand of DNA as a template/model to assemble a strand of RNA.
Here is a diagram showing transcription.
Let’s do transcription!
If DNA =
Then mRNA =
3’
A G C T G A5’
_________________
How does RNA polymerase know where to start and stop making an RNA copy of DNA?
What is the genetic code?

The Genetic Code
Since RNA has only 4 nitrogen bases (A, U, G, C), the code is written in a “language” that only has 4 letters
How is the genetic code read?
Define codon.
TRANSCRIPTION:



The sequence/order of bases in _________ has a code that enables them _______ to find the right
___________________ and assemble them in the correct sequence to synthesize/make a _____________
_____________: Every combination of ___________ “letters” (nitrogen bases or 3 nucleotides) on _________
1 CODON will specify for ___________________
TRANSLATION:




It involves the translation of the ______________________ into amino acids that will make up a protein.
_________________ attaches to the __________
__________ picks up a specific ________________ in the cytoplasm and carries it to the _________ at the
ribosome
___________ contains the _________________ which is 3 unpaired nitrogen bases which will pair with the
______________________
Translation – the details
1.
2.
3.
4.
5.
6.
7.
DNA =
A
T
G
C
T
A
mRNA (codon) =
___________________________
tRNA (anticodon) = ___________________________
SUMMARY of Protein Synthesis
Takes place in the
nucleus
Moves out of the nucleus
into the cytoplasm &
attaches to the ribosome
Chain of AA (a
polypeptide)
SUMMERY: STEPS OF PROTEIN SYNTHESIS
1.
2.
3.
4.
________________________: ___________ makes __________ ( in the _________________)
RNA now becomes mRNA which will leave the nucleus (take the genetic code to ribosome)
mRNA tells ribosome what protein to make
__________ attaches to _________________ and forms a pattern called a __________ to make a
________________.
5. __________ in _____________________ comes to ribosome. It “translates” the codon (codon = 3 nitrogen base
pairs on mRNA) and gets the specific amino acid that matched up with the codon. This is the
____________________. When amino acids are combined together (by peptide bonds) they break off and form
the specific protein needed by the cell. This part is called _______________________
Translation:
Translation is when an mRNA molecule is “read” in the cytoplasm at a ribosome, and tRNA molecules bring amino acids in
the order indicated by the nucleotide sequence of the mRNA molecule to be hooked together into a polypeptide (protein).
Here is a diagram showing translation.
Write the number of the structure indicated in
the diagram next to the correct name.
amino acids
__________
anticodon
_________
mRNA
_________
polypeptide
_________
ribosome
_________
1
2
5
4
3
STEPS TO FIGURE OUT THE GENETIC CODE
1.
2.
3.
4.
A row of DNA bases
Transcribe DNA into mRNA
Translate mRNA into tRNA
Use the codons (mRNA) to translate into
amino acids
Let’s Practice!
DNA
=
mRNA (codon) =
tRNA (anticodon) =
Amino Acid =
Why do some amino acids have more than one code?
 4 nucleotide bases, 3 at a time = 43 = 64
 _____ different amino acids and ____ code words, so
some AA are specified by more than one code word
More Practice!
A T G
___________
___________
____________
DNA =
TAC-GAT-GCC-ATT
mRNA =
____________________
tRNA =
____________________
Amino Acids = _______________________________
Let’s practice translating a message. Start by transcribing the DNA sequence into a molecule of mRNA. Divide the mRNA
into codons by drawing a line between every 3 nucleotides in the mRNA code. Then, write the anticodons that would be
found on the corresponding tRNA molecule. Finally, use the codon chart to determine which amino acid is coded for by
the sequence in the mRNA.
DNA Sequence:
T A C G G G T T C A A C T T G A C T
mRNA Sequence:
_________________________________________________
tRNA Sequence:
_________________________________________________
Amino Acid Sequence:
_________________________________________________
How many codons did you write? __________ How many anticodons did you write? __________ How many amino
acids were coded for (BE CAREFUL!)? ______________
Overview of Protein Synthesis (Gene Expression):
What are the structures labeled 1 & 2?
1. ____________________
2. ____________________
1
This diagram shows only 1 ribosome
translating the message from the mRNA into
the polypeptide (amino acid sequence). Is
this accurate? ___________ Explain why.
_____________________________________
_____________________________________
_____________________________________
When there is an error in the DNA (a
mutation), what can happen to the protein?
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________
If you inherited a trait from one of your
parents, where is this trait coded for in you?
_____________________________________
2
Mutations
-
What would happen if nucleotides did not pair correctly?
What would happen if a nucleotide got squeezed out?
What would happen if an extra nucleotide got put in?
These are all types of DNA, RNA, or protein sequence ______________________.
Mutations are __________________ in the _________________________________.
Types of Mutations
1. Point Mutation –
Remember that the genetic code is read in ____________________________
Normal RNA:
Protein:
ACC
thr
Mutated RNA 1:
Protein:
thr
ACC
leu
Mutated RNA 2:
Protein:
thr
ACC
leu
CUG
leu
UAC
tyr
GGU
gly
CUG
ser
UCC
gly
GGU ACU
thr
UAU
gly
GGU ACU
thr
CUG
tyr
ACU
thr
* NOT ALL MUTATIONS CHANGE THE FINAL OUTCOME*
2. Frame Shift Mutation –
By shifting the sequence, every amino acid will be _______________ following the point of the mutation.
Normal RNA:
Protein:
ACC CUG UAC CGU ACU
thr leu tyr gly thr,
Mutated RNA 1: ACC UGU CCG GUA CU
Protein:
thr cys pro val
___________________ of C & A
Mutated RNA 2: ACC CUG UAC UCG UAC U ____________________of U
Protein:
thr leu tyr try tyr
Chromosomal Mutations
A chromosome is found in the nucleus of a cell and it contains all the genetic information that is passed down from one
generation of cells to the next
What is a chromosomal mutation?
Types of Chromosomal Mutations:
1. Deletion A B C D E F original chromosome
A C D E F deletion of B
2. Duplication ABCDEF
ABCDDEF
original chromosome
duplication of an extra D
3. Inversion ABCDEF
AEDCBF
original chromosome
inversion of B C D E
4. Translocation ABCDEF
ABCJKL
original chromosome
translocation of J K L from another completely different chromosome
Significance of Mutations
1. Harmful Mutations
- What will these types of mutations cause?
These mutations will cause changes in protein structure or gene activity
2. Neutral Mutations
- What effect will they cause on the function of the protein which they code or the expression of genes?
3. Provide a Source of Genetic Variability
-
produce proteins with new or altered activities that can be _________________ to organism in different or
changing environments
mutations are one source of evolution
responsible for developing new and better varieties of crops