ZOO2144/2544 Practical 2: Transcription and Translation [121]
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Student number:
Video: Transcription
https://www.dnalc.org/resources/3d/12‐transcription‐basic.html
Question 1
What are the main types of RNA? What are their functions? [6]
Question 2
Describe the differences between DNA and RNA. [6]
Question 3
Compare and contrast the structures of prokaryotic and eukaryotic mRNAs. [4]
Question 4
What is the function of the promoter? [2]
Question 5
What effect would a mutation in an intron section of a gene have on the expression of the gene?
Explain. [2]
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Practical 2 – Principles of Genetics – ZOO2544 – 2021 – University of Venda
Question 6
The following is a segment of DNA containing the beginning of a gene
3‐ CGTCTACCTATCAGCAGCTGATTAA ‐5
5‐ GCAGATGGATAGTCGTCGACTAATT‐3
6.1 If an RNA polymerase were to transcribe the gene from left to right, is the top or the bottom strand
serving as the template? [1]
6.2 What will be the sequence of the mRNA produced (be sure to label the 5 and 3 ends of your RNA
molecule)? [3]
Question 7
Working with an animal cell culture system, a researcher created random point mutations in the genes
for the RNA polymerases. Individual cells with RNA polymerase mutations were isolated and used to
generate a cell line that expressed that particular mutation. There was only one problem; she did not
know which RNA polymerase was affected in each of the cell lines. To help resolve this question, she
analyzed the levels of different RNAs expressed in each of the cell lines. The results she obtained are
presented below.
Cell Line
Unmutated cells
Cell line A
Cell line B
Cell line C
mRNA
100
100
20
98
RNA expression (%) relative to unmutated cells
U4 snRNA
18S rRNA
Tyrosine tRNA
100
100
100
30
98
40
90
100
95
96
43
100
Which type of RNA polymerase (I, II, or II) appears to be mutated in each one of the cell lines. Explain.
[8]
Question 8
What types of modifications, if any, are done to RNA pol II transcripts? [6]
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Practical 2 – Principles of Genetics – ZOO2544 – 2021 – University of Venda
Question 9
Below is a schematic of gene Y, which encodes protein Y. The promoter region is indicated by the
dotted box. Transcription begins immediately following the promoter.
Promoter
Transcriptional terminator
5’
Exon 1
3’
1 100
Intron 1
2100
Exon 2
4100
Intron 2
6100
Positions 200-203 = Start codon
Exon
8100
10100 base pairs
Positions 8800-8802 = Stop codon
9.1 The transcript first produced by this gene would be approximately how many nucleotides long? [1]
9.2 The transcript from this gene that is used for translation would be approximately how many
nucleotides long? [1]
Question 10 [20]
Fill in the table:
Transcription
Translation
Where does this process occur in
eukaryotic cell?
What is the enzyme that carries out
this process?
What is the template that is read
during this process?
In what direction is the template
read?
What is the start signal/sequence
for this process?
What is the polymer that is formed?
What monomer is used to form this
polymer?
What type of bond is formed
between monomers?
In what direction is the new
polymer formed?
What is the stop signal/sequence for
this process?
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Practical 2 – Principles of Genetics – ZOO2544 – 2021 – University of Venda
Question 11
Below is the double‐stranded DNA sequence of part of a hypothetical yeast genome, which happens to
contain a very small gene. Transcription starts at the Transcription Start Site (TSS) after the promoter
(shown in yellow), and proceeds in the direction of the arrow. Transcription stops at the end of the
Transcription Terminator (shown in blue).
TSS
5’ – CTATAAACTCCGATGGGTAAAACTGCCGTTAGGCATTGACGGAGTATCTCGAA – 3’
3’ – GATATTTGAGGCTACCCATTTTGACGGCAATCCGTAACTGCCTCATAGAGCTT – 5’
promoter
terminator
11.1 Which strand of DNA shown, the top or the bottom, is the template strand? [1]
11.2 What is the sequence of the mRNA produced from this gene? Label the 5’ and 3’ ends. [3]
11.3 What is the sequence of the protein produced from the mRNA in (b)? Label the N and C termini. [4]
11.4 If a mutation were found where a T/A (top/bottom) base pair were added immediately after the
T/A base pair shown in bold, what would be the sequence of the mRNA? What would be the sequence
of the protein? [7]
Question 12
Shown below is a double‐ stranded bacterial (E. coli ) DNA sequence coding for a hypothetical protein.
Both strands are shown; the top strand reads 5’ to 3’ left to right, while the bottom strand reads 5’ to 3’
right to left. The nucleotides are numbered 1 to 100. NOTE: For this problem, transcription begins with
and includes the bold and underlined C/G (top strand/bottom strand) base pair and RNA polymerase
proceeds from left to right along the DNA.
1
20
40
5'-GTGTCCGTCTAATATTGTGAGATGTTATATCCCGCCGTCAACACCATCAA-3'
---------+---------+---------+---------+---------+ 3'CACAGGCAGATTATAACACTCTACAATATAGGGCGGCAGTTGTGGTAGTT-5'
60
80
100
5'-ACAGGATAATCGCCTGCTGGGGCAAAGGCGGTGAAGGTAAAGGTGTTGCC-3'
---------+---------+---------+---------+---------+ 3'TGTCCTATTAGCGGACGACCCCGTTTCCGCCACTTCCATTTCCACAACGG-5'
12.1 Which strand is used as a template for transcription, the top or the bottom? [1]
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Practical 2 – Principles of Genetics – ZOO2544 – 2021 – University of Venda
12.2 Where would the promoter be relative to the start of transcription? [1]
12.3 What are the first 15 nucleotides of the resulting mRNA? Indicate the 5' and 3' ends of the mRNA.
[3]
12.4 What are the first 5 amino acids translated from the resulting mRNA? Indicate the amino (NH3+)
and carboxy (COO‐) termini of the protein. [4]
12.5 Do the underlined nucleotides TAA (indicated and underlined in grey) encode a stop codon for the
protein? Briefly explain your answer. [2]
Consider the situations in parts (6‐8) independently:
12.6 A mutation occurs which results in the insertion of an extra G/C (top strand/bottom strand) base‐
pair immediately after base pair 11 (shown in bold). What effect will this insertion mutation have on
the mRNA transcript and resulting protein? [3]
12.7 A different mutation results in the substitution of the T/A base pair at position 30 (shown in bold
and underlined) with a G/C base pair. How would this mutation affect the sequence of the protein that
is produced? [3]
12.8 A mutation occurs which results in the substitution of the C/G base pair at position 42 (shown in
bold italics) to a T/A base pair. How would this mutation affect the sequence of the protein that is
produced? [3]
Question 13
A mutation is found in a tRNA ‐encoding gene. The wild type allele produces a tRNA that recognizes the
codon GAA, and is charged with the amino acid Glutamic acid. The mutant tRNA is still charged with
Glu, but the anticodon is mutated such that it recognizes the codon TAA. What effect will this have on
translation in these cells? How will the proteins produced be different? [4]
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Practical 2 – Principles of Genetics – ZOO2544 – 2021 – University of Venda
Question 14
Follow each step using the illustration below:
1.Fill in the complimentary DNA strand using DNA base pairing rules.
2. Fill in the correct mRNA bases by transcribing the bottom DNA code.
3. Translate the mRNA codons using the Codon Table found below/ Write the name of each
amino acid in the oval
4. Write in the correct anti‐codon the tRNA molecule.
5. Respond to the questions about protein synthesis below the amino acids.
Complete the following using the directions and codon table: [4]
A
6
T
G
C
A
A
G
A
G
A
T
C
C
C
A
Practical 2 – Principles of Genetics – ZOO2544 – 2021 – University of Venda
14.1 Where is mRNA synthesized, in translation or transcription? [1]
14.2 How might a “mistake” in one DNA base affect a protein? [5]
Follow the same directions using the information shown below: [4]
A
T
G
C
G
A
G
T
C
A
G
C
T
C
A
Question 15
You are studying a very short protein‐ encoding region whose sequence is shown below. The region
of sequence shown is from the transcriptional start site to the transcriptional stop site. This region
encodes two different polypeptides. The region’s one small intron is shown for you in bold.
5’-CTACGTACTATGTATTCCGATCTATACTCGATCTAGTCGCATTCCGATAAGATCGTAC-3’
3’-GATGCATGATACATAAGGCTAGATATGAGCTAGATCAGCGTAAGGCTATTCTAGCATG-5’
15.1 What are the sizes of the two polypeptides? [2]
15.2 Which strand is used as a template in transcription for the smaller polypeptide, the upper strand or
the lower strand? [1]
15.3 How many nucleotides long would the final processed mRNA made from this gene be (not including
the 5’ cap and the 3’ polyA tail)? [1]
15.4 What is the sequence of the smaller polypeptide [4]
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Practical 2 – Principles of Genetics – ZOO2544 – 2021 – University of Venda