PROTEIN SYNTHESIS – (putting our genes to work!) Chapter 8.4-8.5 in online textbook
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Proteins are composed of_________________. They are the building blocks of all
proteins.
The genetic information encoded within the DNA molecule is the information necessary
for the manufacture of______________. There are _______different amino acids found
in the proteins of living organisms. All the different proteins in an organism are made of
these same ______ amino acids.
Each sequence of _______ nucleotide bases forms a chemical “code word”
or_________, which codes for a particular amino acid. The order in which the code
words are ______________in the DNA molecule determines the order of the amino
acids in the protein molecule that the DNA codes for.
THE ____________________________________________OF AMINO ACIDS
DETERMINE THE SHAPE OF A PROTEIN. THE _________________OF A PROTEIN
gives it certain chemical properties and therefore, DETERMINES
ITS________________!
Proteins are synthesized in the cytoplasm at the_______________. The encoded
instructions however, are located in the_____________, where the DNA molecule
resides. The instructions in the DNA molecule are not used directly to manufacture the
protein. Instead, protein synthesis is a two-step process and is the job
of_______________.
RNA, _______________________________
RNA is found both in the _________________and____________. It has some
similarities with DNA but there are some important differences. Both similarities and
differences can found in the following chart:
Characteristic
Building block
Location
Nitrogen bases
Sugar
Number of strand
Types
DNA
Nucleotides
Nucleus only
Guanine, Cytosine, Adenine,
& Thymine
deoxyribose
Two (double stranded)
DNA
RNA
Guanine, Cytosine, Adenine,
&
STEPS OF PROTEIN SYNTHESIS:
The first stage of protein synthesis is____________________. TRANSCRIPTION is the process of
transferring the genetic code in DNA to_________________________________. (Performed
in_____________)
1. A gene (one section of DNA) is unzipped by the enzyme _________ breaking the
___________ _________ between the nitrogen bases. Another enzyme called
_____ _____________ binds to “read the exposed gene. Only ___________of the DNA
strands, designated as the “_______________” strand, actually encodes information for
making the___________________.
2. The ______________nucleotides are aligned in a complementary manner to the DNA
____________strand. ________________in RNA pairs with adenine in DNA. As the
mRNA nucleotides line up along the DNA template, the sugars & phosphates are joined
together by ___________________bonds by an enzyme called
____________________________ to form a ____________long strand. The synthesis of
the mRNA can only occur in a _______________________direction!
3. The completed mRNA molecule __________________from the DNA, leaves the nucleus
& moves through the cytoplasm out to a_____________________. The DNA strands
come back together & coil back up into their _______________________form.
Figure 1: Pairing of mRNA with DNA
DNA sense
strand
Exercise 3: Transcription
1. Refer to Exercise 3 of the data sheet. The right-handed strand represents the sense strand of the DNA. The left-hand
strand represents the messenger RNA that is being produced off the DNA template.
2. Fill in the DNA bases on the sense strand. Use the original sequence of bases from the right side of the DNA molecule
in Exercise 1. Color and label all the components of the DNA sense strand using the same color code as in Exercise 1.
3. Next, color the mRNA molecule. Color the ribose sugar brown to distinguish it from the purple deoxyribose. Label all the
ribose sugars with an “R” and all the phosphates with a “P”.
4. To complete the mRNA molecule, draw in bases that are complementary to the bases in the DNA sense strand. Use
the same symbols as in Exercise 1 EXCEPT substitute the base uracil in place of Thymine in the RNA molecule. Use the
symbol for uracil shown at the left. Color and label the mRNA bases. Use the same color code as in Exercise 2, BUT use
orange for uracil, instead of yellow for Thymine.
5. Show the hydrogen bonds between the paired bases, as in Exercise 1 and 2. Next, label the 3’ and 5’ ends of the newly
synthesized mRNA molecule and the sense strand of the DNA molecule.
6. The finished mRNA should have 3 sets of nitrogen bases. Each set of three is a codon, that is a “code word” for a
single amino acid. On the mRNA molecule, indicate each codon with a bracket and label them from top to bottom (5’ to 3’)
as C#1, C#2, and C#3.
The second stage of Protein Synthesis is_____________________.
TRANSLATION is when the information in the mRNA is “______________” and the
________________assembled. ______________________are brought in, positioned in the correct
sequence, and joined together to form a protein. (continued from #3 of transcription)
1. The ___________ end of the ____________molecule and the
_________________________combine.
2. The ribosome moves along the mRNA molecule in a __________________direction, reading one
______________at a time. For example, in Figure 6 below, the first codon at the 5’ end is read as
“AUG” not “GUA”. MRNA is approximately 1000 or more bases long but read in groups of
______________which make a _______________- the code word for an amino acid.
Amino acid
Figure 2: Direction Translation of mRNA – 5’ to 3’
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___________________RNA (rRNA) consists of one large and one small subunit for each
ribosome. A ribosome also contains____________. These subunits hold the
____________and ___________in the right position so ____________________can be
joined. Several ribosomes often move along a single mRNA.
3.As the ribosome moves down the mRNA molecule, a third type of RNA called
_____________________(tRNA) brings specific ____________________to the mRNA/ribosome
complex to be joined together. Although it is single-stranded, it is folded back on itself and has a
___________________shape. (See Figure 7).
Figure 3: Diagram of tRNA molecule
4. _____________acts as a “___________” for amino acids,
picking them up in the __________________and carrying
them to the_________________. At the _________ end of
the tRNA molecule is an area called the
____________________attachment site where the amino
acid binds to the tRNA. Each tRNA only carries
___________particular type of amino acid.
5. At the _____________of each tRNA molecule in the
bottom “loop”, is a special sequence of 3 nucleotides called
the_________________. The anticodons in the tRNA are
complementary to the ________________in mRNA. When
the tRNA brings an amino acid to the ribosome, it is
positioned in the proper place (sequence) by
__________________its anticodon with the codon in the
message of mRNA. After “dropping off” an amino acid, the tRNA’s are _________________and can
combine to another molecule of the _____________amino acid to repeat the process if needed.
 As the _______________come in, they are linked together by
_____________________and this chain of amino acids forms a
___________________chain.
 The process continues until a _____________codon is reached.
 If the polypeptide chain is functional, it forms a_____________. However, many
times, it takes _____________polypeptide chains to form a protein.
Exercise 4: Translation
1. Refer to Exercise 4 of the data sheet. The strand on the left side of the page is the mRNA molecule. Fill in the missing
bases on the mRNA using the same mRNA sequence from Exercise 3.
2. Color and label the bases, sugars, and phosphates using the same color code as in Exercise 3. Indicate the codons in
the message with brackets and label them C#1, C#2, and C#3 as in Exercise
3. The objects drawn to the right of the mRNA represent three molecules of tRNA. Like mRNA, each tRNA is composed of
a long chain of nucleotides but only the anticodon portion is shown in detail here. Fill in the missing bases in the anticodon
region. Remember, they must be complementary to the bases in the mRNA molecule. Color and label the 3 nucleotides of
the anticodons, using the same color code as above.
4. The last step is to determine which amino acids these three tRNA molecules are carrying. Refer to the chart provided to
determine the identity of these three amino acids. Note that the chart provided is set up for mRNA codons, not DNA
code words or tRNA anticodons!!! When determining the amino acids, make sure to refer to the codons in the mRNA,
NOT the anticodons in the tRNA. In Figure 8, the first codon is AGC, which codes for the amino acid serine. Write the
names of the three amino acids being carried by each tRNA in the space provided using your codon wheel.
Mutations in DNA: Chapter 8.7 in online textbook
A _________________is any alteration in the nucleotide base sequence in the DNA molecule.
Significance of Mutations
 Some mutations occur spontaneously due to random errors that occur
during___________________. More often, however, mutations are caused by
______________________(chemicals or radiation) that damage the DNA.
Mutation)- In a substitution, ____nucleotide base is substituted for another in the DNA,
changing the ____________of bases.
• When such damage occurs, if the damage is not repaired correctly, a mutation results.
• Mutations result in _________ _ __ _________within a species. Even though mutations are
rare, they are the ultimate source of _____ _________within a species.
One common type of mutation is the ___________________(OR POINT MUTATION).
•The consequences of such a mutation vary.
– Ex. GACTGACTG
GACTGCCTG
Types of Point Mutations:
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Substitution mutations:
Some amino acids have ________________word that codes for them. In some cases, the
new code word codes for the ______________amino acid as the original. This is referred to
as a _______________________mutation because even though the DNA code has changed,
there is ______________in the ___________________sequence of the protein.
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In other cases, the new code word codes for a _________amino acid than the original code
word. When this happens the protein coded for will have a different amino acid sequence than
the original and may or may not function properly. This type of mutation is called a
____________________mutation.
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Occasionally, the new code word is a _______________________codon that causes a
premature stop signal at the wrong place in the message. In this case, the encoded protein is
_________produced at all. This type of mutation is referred to as a
____________________mutation.
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FRAMESHIFT MUTATION. In this type of mutation, a nucleotide is either ____________or
____________ to the strand at some point along the strand. If this occurs,
____________amino acid from the point of the mutation will be changed.
When many nucleotides are involved mutations are called CHROMOSOMAL MUTATIONS.
These occur during sex cell (sperm & egg) formation.
Chromosomal Mutations
Involves changes in the _____________________of chromosomes or the total number of
chromosomes (which are large portions of DNA) which can cause severe deformities and many times
death.
Types of Chromosomal Mutations:
____________ – part of chromosome is permanently
missing
____________ – part of chromosome is copied and
repeated
___________ – chromosome breaks off and reattaches in
reverse
______________– chromosome breaks off and attaches to
another chromosome.
Mutations Exercise:
Use the following DNA molecule to answer the following questions.
AATGCCAGTGGTTCGCAC
1. Write the base sequence of the complementary DNA strand.
2. Using the original DNA code, write the base sequence that would appear on an mRNA strand
after transcription.
3. Determine the order of amino acids in the resulting protein fragment. There is no start or stop
in the sequence.
4. If the forth base in the original DNA strand were changed from G to C, how would this affect
the resulting protein fragment?
5. If a G were added to the original DNA strand after the third base, what would the resulting
mRNA look like?
How would this addition affect the protein? Give the sequence of amino acids.
6. Which change in DNA was a point mutation?
Which was a frameshift mutation?
7. In what way did the point mutation affect the protein?
8. How did the frameshift mutation affect the protein?
OR