Download Compare the activities of the enzymes in prokaryotic transcription to

UNIVERSITY OF TECHNOLOGY, JAMAICA
FACULTY OF SCIENCE AND SPORTS
SEMESTER 1: Tutorial
DATE:
October 13, 2010
GROUP:
SUBJECT: Cell and Molecular Biology
1. Compare the activities of the enzymes in prokaryotic transcription to those in
Eukaryotic transcription.
2.
Summarize the posttranscriptional changes made to tRNA and rRNA
transcripts.
3.
The nucleotide sequence of the antisense strand of a double helical DNA
molecule is
TACAAAGTATGACTATCTCCCCAAATT
i.
ii.
What is the nucleotide sequence of the complementary strand?
What will be the nucleotide sequence of the mRNA that is transcribed
from this DNA?
iii.
What is the amino acid sequence of the polypeptide that this DNA
sequence encodes?
3.
The genetic code is organized into units called codons.
i.
ii.
iii.
iv.
What constitutes a codon?
How many different codons are possible, based on the structural
organization of individual codons?
How many different codons are there that specify amino acids in the
"standard" version of the genetic code?
What is the function of the codons that do not code for amino acids?
v.
Compare the number of amino acid-coding codons with the number of
amino acids that are coded for and explain how cells deal with the
discrepancy in the two numbers.
vi.
What additional features would you expect to see upstream from the
coding sequence for a protein?
What additional features would you expect to see downstream from
the coding sequence for a protein?
vii.
viii.
What added complication might you encounter with eukaryotic DNA?
4.
Summarize the modifications that must be made to mRNA transcript
before it can be translated.
5.
During translation, mRNA is read ___ to ___ and the protein is translated _____
terminus to ____ terminus.
6.
Describe the sequence of events involved in assembling together the
messenger RNA, the ribosomal subunits, and the first two amino acids
involved in translation of a specific protein. Include in your summary a
brief description of the various accessory molecules and carrier molecules
that are involved.
7.
Describe the function of each of the following in translation: codons, tRNA
synthetase, peptidyl transferase, E site of the ribosome, A site of the ribosome, P
site of the ribosome, mRNA, tRNA, rRNA, initiation factors, elongation factor
Tu, elongation factor G, release factor
8.
Imagine that a mutation occurs in the DNA in gene X that changes a trp codon
(UGG) in the codling sequence to a stop codon (UGA). In which case (a or b)
will this mutation in gene X be the most deleterious to the cell?
a. The original trp codon is located at the beginning of the coding sequence for
the
protein X
b. The original trp codon is located at the end of the coding sequence for the
protein X
Explain your answer, telling what will happen during translation and how this
will affect the function of the protein X.
9.
Compare translation in prokaryotes with that in Eukaryotes.
10.
Strepromycin is an antibiotic that binds the P site on the ribosome of E. coli and
blocks the binding of the tRNA. Chloramphenicol inhibits the peptidyl
transferase of bacterial ribosomes. Explain why these drugs can be used as
antibiotics against bacterial infections
Describe two features of the genetic code.
(
11.
12.
How does the attachment of mRNA to ribosomes differ between eukaryotes and
prokaryotes?