Download Protein Synthesis and Mutations Review Explain the differences and

Protein Synthesis and Mutations Review
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Explain the differences and similarities between DNA and RNA.
Nucleic Acid
Sugar
Bases
Strands
DNA
Deoxyribose
ATGC
2-double helix
RNA
Ribose
AUGC
1-single strand
Given a sequence of DNA, be able to write the DNA copy, the RNA transcript, the codons,
the anticodons and use a table to determine the amino acids.
a. Transcribe the following DNA sequence into mRNA (codons):
A – G –– A – T – A – C – G– C – G –C – C –T –A
U – C -- U – A – U – G – C – G – C – G –G –A –U
b. Below is a list of the mRNA codons for each amino acid.
Alanine: GCU
Arginine: CGU
Asparagine: AAU
Aspartic Acid: GAU
Cysteine: UGU
Glutamic Acid: GAA
Glycine: GGU
Histidine: CAU
Isoleucine: AUU
Leucine: UUA
Lysine: AAA
Methionine: AUG
Phenylalanine: UUU
Proline: CCC
Serine: UCU
Threonine: ACU
Tryptophan: UGG
Tyrosine: UAU
Valine: GUU
Terminator: UAA
If the sequence on the DNA molecule calls for a protein with the following DNA codons, (1)
what would be the sequence on the mRNA and (2) what would be the amino acid sequence
of the protein being made?
DNA
TAC
TTA
mRNA
AUG
UUA GUU UGG UAU UAA
Amino Acids:
Met
Leu
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CAA ACC ATA ATT
Val
Trp
Tyr
Terminator (Stop)
In the DNA sequence : TACTTACAAACCATAATT
a. What would be the effect if one of the bases were deleted in the very first mRNA
codon? Frameshift Mutation, which would cause a change in 1 or more amino acids,
altering the protein possibly causing a faulty or nonfunctional protein.
b. What would happen if there was a substitution of one base for another in one of the
mRNA codons? Point mutation, which could cause a change in 1 amino acid, cause a
premature stop codon causing a faulty protein to be made, or no change at all could
occur.
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Mutations that occur at one single nitrogen base are referred to as __point__ mutations. A
mutation involving the insertion or deletion of a nucleotide is called a ___frameshift_____
mutation.
In DNA what are the complementary nucleotide pairs? In RNA what are the complementary
nucleotide pairs? A-T & G-C; A-U & G-C
What are the three types of RNA? Include the functions and shapes of
each.
rRNA-along with protein, makes up the ribosomes
tRNA-transfers amino acids to the ribosomes where proteins are
synthesized
mRNA-copies DNA’s code & carries the genetic information to the
ribosomes
Draw or explain the structure of the ribosome? What is the purpose
of the ribosome? Protein Synthesis
Explain the process for protein synthesis to occur, in detail. Where does each stage occur
and what are the steps at each stage?
In the Nucleus: First the DNA must be unpackaged (unwrapped) from the proteins so that
the gene becomes exposed. Then Transcription factors must help bind the RNA polymerase
to the promoter region on the DNA. RNA polymerase will then unwind the DNA chain while
walking down using the template strand to transcribe the DNA sequence into a mRNA
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strand. Once finished the mRNA strand may be further processed by alternative splicing (if
needed) to create the final mRNA strand that is then taken out of the nucleus into the
cytoplasm where the small ribosomal subunit will bind with it. The small ribosomal subunit
(with the mRNA strand) will then bind with the large ribosomal subunit. The ribosome will
then scan the mRNA strand looking for the “Start” codon (AUG). tRNA will bring in the
amino acids by matching the codons on the mRNA with their anticodons. This process
begins at a site called the P site in the ribsosome (where the polypeptide (protein) strand
will grow). Next another tRNA will come in with the correct anticodon to the next codon in
the A site and a peptide bond will form between the two amino acids. The ribosome will
then move down the mRNA sequence so the next codon is in the A site, and then next tRNA
can come in bringing in the next amino acid. This will continue until the ribosome comes
upon to a terminator codon, thus causing the ribosome to release both the protein (amino
acid strand) and the mRNA.
In the diagram below, label which process is Transcription and which is Translation.
a. For Transcription label the template strand, the mRNA, and draw in where the RNA
polymerase would be
b. For Translation label the start codon, the tRNAs, the amino acids, the mRNA and the
ribosome
c. Below each diagram write Define Transcription. Define Translation.
What is a codon? How many nucleotides make up a codon? What is an anticodon? Where
are codons and anticodons found? A codon is sequence of 3 nucleotides that together form
a genetic code in DNA & RNA. 3 nucleotides make up one codon. An anticodon is the
complementary sequence on the tRNA that matches the codon on the mRNA. Codons are
found in DNA and mRNA, anticodons are found on tRNA.
Briefly describe how eukaryotes and prokaryotes control their gene expression.
Eukaryotes regulate their gene expression through 1)DNA/Gene packaging where the DNA is
wound around proteins limiting access to the RNA polymerase for transcription. 2)
Transcription Factors are proteins that bind to the DNA and help RNA polymerase bind to
the promoter region in order to transcribe the gene into mRNA. 3) RNA Alternative Splicing
is where after DNA is transcribed, intron (noncoding sequences) are cut out of the gene and
removed while the exons (coding sequences) are pieced back together to make the protein.
Some genes have the ability to have 2-3 different proteins pieced back together from their
exons.
Prokaryotes have their genes under the control of an operon (which is a sequence of DNA
that contains an operator sequence, promoter sequence, and the gene). Repressors bind to
the operator sequence preventing RNA polymerase from being able to bind to the promoter
sequence and transcribe the DNA. There are two types of operons, 1) Repressible operons
which are normally transcribing the DNA into mRNA to create protein and when we need to
turn off the gene a repressor is activated and binds to the operator region preventing
further transcription. 2) Inducible operon where the gene is normally turned off because the
repressor is bound and when the gene needs to be turned on to make the protein, a inducer
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binds to the repressor removing it from the operator sequence and therefore allows RNA
polymerase to bind and make the mRNA transcript.
Describe what an operator is and its function. What does a repressor protein do? An
operator is sequence of DNA that transcription factors/repressors bind to in order to
regulate the gene expression (turn the genes on or off). A repressor protein binds to the
operator sequence and blocks RNA polymerase from being able to bind and transcribe the
DNA.
Describe exons and introns. What are the functions of each? Exons are the part of a gene
that code for protein. Introns are nucleotide sequences that are removed during RNA
splicing.
Describe Alternative RNA splicing. Why do we need alternative splicing? RNA Alternative
Splicing is where after DNA is transcribed, intron (noncoding sequences) are cut out of the
gene and removed while the exons (coding sequences) are pieced back together to make
the protein. Some genes have the ability to have 2-3 different proteins pieced back together
from their exons.
What are the two types of mutations and their subtypes? Point Mutation  Substitution
(where a nucleotide is swapped for a different nucleotide); Frameshift  Insertion(the
addition of 1 or more extra nucleotides) or Deletion (the removal of 1 or more nucleotides
from the DNA sequence).
a. Which type of mutation is most likely to have the least effect on protein synthesis?
Point mutation
b. Which type of mutation is most likely to have the most harmful effect on protein
synthesis? Frameshift mutation
Amino acids
Template Strand
Ribosome
tRNAs
RNA polymerase
Transcription
Start codon
Ribosome
Translation