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Integrated Science Worksheet
Chapter 8
Name ___________________________
Period _____________
Protein Synthesis
/10
Protein synthesis is a complex process. In this activity you will trace the steps that are involved in the synthesis of
a protein molecule called oxytocin. Oxytocin is the pituitary hormone that helps regulate blood pressure, stimulates
the uterus to contract during childbirth, and stimulates the production of milk after childbirth.
A. Transcription. Protein synthesis begins with DNA in the nucleus. Below is a DNA base sequence that could
code for part of a molecule of oxytocin. Write the sequence of messenger RNA (mRNA) codons that would result
from the transcription of this portion of DNA. The arrow marks the starting point.
ACA
DNA:
ATA
1
TAG
2
CTT
3
4
TTG
5
ACG
GGG
6
7
AAC
CCC
8
ATT
9
10
mRNA: ________ ________ ________ ________ ________ ________ ________ ________ ________ ________
B. Translation. After transcription, mRNA leaves the nucleus and attaches to a ribosome, where translation takes
A
G
U
C
Lysine
Lysine
Asparagine
Asparagine
Glutamic Acid
Glutamic Acid
Aspartic Acid
Aspartic Acid
“Stop” codon
“Stop” codon
Tyrosine
Tyrosine
Glutamine
Glutamine
Histidine
Histidine
Arginine
Arginine
Serine
Serine
Glycine
Glycine
Glycine
Glycine
“Stop” codon
Tryptophan
Cysteine
Cysteine
Arginine
Arginine
Arginine
Arginine
Isoleucine
Methionine/Start
Isoleucine
Isoleucine
Valine
Valine
Valine
Valine
Leucine
Leucine
Phenylalanine
Phenylalanine
Leucine
Leucine
Leucine
Leucine
G
U
Second Letter in Codon
A
Threonine
Threonine
Threonine
Threonine
Alanine
Alanine
Alanine
Alanine
Serine
Serine
Serine
Serine
Proline
Proline
Proline
Proline
A
G
U
C
A
G
U
C
A
G
U
C
A
G
U
C
Third Letter in Codon
First Letter in Codon
Genetic Code Chart
place. Each mRNA codon bonds with an anticodon of transfer RNA (tRNA) and each tRNA carries a specific amino
acid. The genetic code chart below shows the mRNA codons and the amino acids for which they code. For
example, if you were given the codon AGA, you can see that these bases code for the amino acid arginine.
C
Use your mRNA sequence from Part A to write the sequence of amino acids in this part of the oxytocin molecule.
1_________________
2_________________
3_________________
4_________________
5_________________
6_________________
7_________________
8_________________
9_________________
10_________________
1. How many amino acids make up this portion of the oxytocin molecule? ________________________________
2. What is the purpose of the UAA codon?__________________________________________________________
C. Overall Process of Protein Synthesis
Label the structures on the diagram using the
structures listed below.
ribosome
tRNA
mRNA
Cell Membrane
DNA
Nucleus
1.
Amino Acid
Sequence
2.
3.
4.
mRNA