RNA & Protein Synthesis
Essential Question:
How do our cells determine who we are?
Why are proteins important to living things?
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•
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Control rate of chemical reactions as _e__________
nzymes
Building materials for skin, bone, and _m_________
uscles
ntibodies
Help fight infections as _a__________________
Help control what goes in and out of cell through cell
_m____________________
embranes
1. What is a gene?
• Small section of DNA that holds code for making a
particular protein, or for particular trait.
2. What is RNA? How is it different from DNA?
• Ribonucleic acid.
• DNA has two strands, RNA only has one.
• RNA has U (uracil) instead of T (thymine). The
other bases are the same (A, G, C).
3. What happens to DNA in the process of transcription?
• DNA in nucleus is “unzipped.” A copy of one
strand is made in the form of messenger RNA
(mRNA)
Adenine (DNA and RNA)
Cystosine (DNA and RNA)
Guanine(DNA and RNA)
Thymine (DNA only)
Uracil (RNA only)
mRNA
DNA
4. Proteins are made by joining ___________________
amino acids
into long chains called polypeptides.
Protein
molecule
5. Each polypeptide
contains a combination
of how many different
amino acids?
20
__________
6. “Words” in the genetic code of DNA and RNA are
3
made up of how many bases? __________
7. How are codons translated into different amino acids?
• Codon made up of
3 nucleotide bases,
e.g. AAG, CUA, etc.
• Each set of 3 bases
translates into
different amino
acid, e.g. AAG =
lysine,
leucine
• CUA = _________
8. What do “start” and “stop” codons do?
• Start = beginning of
polypeptide
• Stop = end of polypeptide.
• If protein = paragraph,
polypeptide = sentence,
amino acids = words.
Quick Lab: How does a cell interpret DNA?
1. A certain gene has the following sequence of
nucleotides:
GACAAGTCCACAATC
Write this sequence on your sheet of paper.
2. From left to right, write the sequence of the
mRNA molecule transcribed from this gene:
C UGUUC AGGUGUU AG
Quick Lab: How does a cell interpret DNA?
3. Look at Figure 12-17.
Reading the mRNA
codons from left to right,
write the amino acid
sequence of the
polypeptide translated
from the mRNA.
CUGUUCAGGUGUUAG
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CUG = ______________
Leucine
Phenyl-alanine
UUC = ______________
Arginine
AGG = ______________
UGU = ______________
Cysteine
Stop
UAG = ______________
Quick Lab: How does a cell interpret DNA?
4. Repeat step 3, reading
the codons from right to
left.
CUGUUCAGGUGUUAG
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•
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Aspartic acid
GAU = ______________
Cysteine
UGU = ______________
GGA = ______________
Glycine
Leucine
CUU = ______________
GUC = ______________
Valine
Analyze and Conclude
1. Why did steps 3 and 4
produce different
polypeptides?
Reading bases from left to
right produces different
codons from reading right
to left.
Analyze and Conclude
2. Do cells usually
decode nucleotides in
one direction only or in
either direction?
Usually one direction only
9. What happens to messenger RNA (mRNA) in the process
of translation?
• mRNA is translated into chains of amino acids that
form proteins.
9. What happens to messenger RNA (mRNA) in the process
of translation?
• mRNA is translated into chains of amino acids that
form proteins.
10. Explain the role of the following in protein synthesis:
a. gene
Contains code for making a protein
10. Explain the role of the following in protein synthesis:
b. mRNA
Copy of gene that can be taken out of nucleus into
cytoplasm.
Adenine (DNA and RNA)
Cystosine (DNA and RNA)
Guanine(DNA and RNA)
Thymine (DNA only)
Uracil (RNA only)
mRNA
DNA
10. Explain the role of the following in protein synthesis:
c. tRNA
Transfers amino acids over to mRNA, where they can be
joined together to form protein.
10. Explain the role of the following in protein synthesis:
d. codon
3-letters/bases on mRNA that holds code for 1 amino
acid
10. Explain the role of the following in protein synthesis:
e. anticodon
3 letters/bases on tRNA that match with codon on mRNA
anticodon
codon
10. Explain the role of the following in protein synthesis:
f. ribosome
Helps join amino acids together to form protein/polypeptide
ribosome
10. Explain the role of the following in protein synthesis:
g. amino acid
Molecules that join together to form protein
Protein
molecule
Video: Protein Synthesis
http://www.youtube.com/watch?v=D3fOXt4MrOM
Pop Quiz: Copy the codons below and identify the corresponding
amino acids. p. 303
1.
2.
3.
4.
5.
GCU = __________
alanine
CAA = __________
glutamine
UGG = __________
tryptophan
AUG = __________
methionine
histidine
CAU = __________
Your name at bottom