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SMU-DDE-Assignments-Scheme of Evaluation
PROGRAM
SEMESTER
SUBJECT CODE &
NAME
BK ID
DRIVE
MARKS
Q.No
1
A
2
A
MSC BIOINFORMATICS
2
BI0029
MOLECULAR BIOLOGY
B0827
WINTER 2015
60
Criteria
Marks
Total Marks
Discuss the phenomenon of Rho-dependent and Rho-independent termination of transcription
in prokaryotes.
(Unit 3, Page No. 86)
Explanation for Rho-dependent termination of transcription in
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prokaryotes:
 The rho-dependent terminator received its name
because it is dependent on a specific protein called a
rho factor.
 This protein binds and runs along the mRNA towards
the RNA polymerase.
 When ρ-factor reaches the RNAP, it causes RNAP to
dissociate from the DNA, terminating transcription.
Explanation for Rho-independent termination of transcription
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in prokaryotes:
 The rho-independent termination is simpler of the two
systems and as a result is also called simple
termination.
 The rho-independent signal is found on the DNA
template strand.
 It contains a stretch of sequences which is repeated
again a few base pairs away in the inverted sequence.
 When this stretch is transcribed into an RNA
sequence, the RNA can fold back and base pair with
itself forming a hairpin loop terminating the
transcription.
Explain any six differences between DNA and RNA. Add a note on Griffith’s ‘Bacterial
transformation experiment’.
(Unit 1, Page No. 20, 22)
Six of the following differences between DNA and RNA.
6X1
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DNA
RNA
Double
polynucleotide Single
polynucleotide
chains.
chain.
Larger molecular mass
Smaller molecular mass.
SMU-DDE-Assignments-Scheme of Evaluation
Always a double helix
May have a single or
double helix.
is Pentose sugar is ribose.
Pentose
sugar
deoxyribose
The bases are adenine,
guanine, cytosine
and
thymine.
Found entirely in the
nucleus
The bases are adenine,
guanine,
cytosine
and
uracil.
Made in the nucleus but
found throughout the cell.
Permanent
Temporary- exists for a
short time.
Exists in one form only
Exists in many forms
messenger, ribosomal and
transfer RNA etc.,
Griffith’s ‘Bacterial transformation experiment’:
 Griffith carried out experiment on the bacterium
Streptococcus pneumoniae.
 S. pneumoniae exists in two forms: Harmful form and safe
form.
 His experiments can be summarized as follows:
a. S-strain kills mouse;
S-strain + Live mouse  Dead mouse(S-strain recovered)
b. R-strain does not kill mouse;
R-strain + Live mouseLive mouse(No bacteria
recovered)
c. Heat killed S-strain does not kill mouse:
Heat killed S-strain + Live mouseLive mouse(No
bacteria recovered)
d. R-strain + heat killed S-strain kills live mouse.
Live S-strain  Heat killed + R-strain +Live
mouseDead mouse
(Encapsulated strain recovered).
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 When live bacteria isolated from the dead mouse after
mixed infection, S-type bacteria were obtained. The live R
bacteria had been transformed into the harmful S bacteria.
Griffith called the substance responsible for the
transformation as the ‘Transforming principle’.
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Explain any five causes of cancer.
Explanation for any five of the following causes of cancer:
a. Retroviruses
b. DNA viruses
c. Hereditary predisposition
(Unit 8, Page No. 234 )
5X2
10
SMU-DDE-Assignments-Scheme of Evaluation
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A
d. Ionizing radiation
e. Ultraviolet light
f. Chemical mutagens
Describe the process of RNA editing. Explain its types.
Description for the process of RNA editing:
 RNA editing is a process in which the information content
is altered in a RNA molecule through a chemical change
in the base makeup.
 Till date, this process is observed in eukaryotes, not in
prokaryotes.
 RNA editing occurs in the cell nucleus, cytosol, as well as
in mitochondria and plastids, which are thought to have
evolved from prokaryotic-like endosymbionts.
Explanation for the types of RNA editing:
a. Editing by insertion/deletion:
 RNA editing through the addition of Uracil has been
found in mitochondria from kinetoplastid protozoa.
 This uses a guide RNA (gRNA) that is complementary
to the region to be changed, with some differences.
 The gRNA binds to the region to be edited, and the
differences are copied from the gRNA to mRNA. This
is typically seen in mitochondria and the functional
effect is often a frameshift.
b. Editing by deamination:
C-U editing: This type of editing involves Cytidine
deaminase that deaminates a Cytosine base into a Uracil
base.
 An example of C to U editing is with the
apolipoprotein B gene in humans. Apo B100 is
expressed in the liver and apo B48 is expressed in the
intestines. The B100 form has a CAA sequence that is
edited to UAA, a stop codon, in the intestines. It is
unedited in the liver.
A-I editing: this has been found in large genes with
extensive areas of double stranded RNA.
 During translation, I pairs as if it is G.
 The enzymes responsible for A-to-I editing are called
the adenosine deaminases.
 Long extended dsRNAs undergo massive editing,
whereas RNA duplex structures with bulges and loops
are subject to site-selective editing, as observed in
several neurotransmitter receptor mRNAs ensuing
(Unit 4, Page No. 128)
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SMU-DDE-Assignments-Scheme of Evaluation
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single amino acid substitutions.
 The deficiency or mis-regulation of A-to-I RNA
editing has been implicated in the etiology of
neurological diseases, such as epilepsy, amyotrophic
lateral sclerosis (ALS), and depression in mammals.
Explain the four levels of eukaryotic gene regulation.
(Unit 6, Page No. 192)
Explanation for the four levels of eukaryotic gene regulation:
3+2+2+3
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 Regulation at Transcriptional Level. (3 Marks)
 Post-transcriptional Modification. (2 Marks)
 Translational control (2 Marks)
 Post translational control (3 Marks)
Define genetic code. Describe any eight features of genetic code.
(Unit 5, Page No. 158)
Definition of genetic code:
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Genetic code is a set of rules by which information encoded
within genetic material is translated into proteins.
Eight features of genetic code:
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1. Each codon contains three bases that code for one
aminoacid.
2. The codons do not overlap
3. Most of the aminoacids have more than one codon. Many
codons that codes for only one aminoacid differ from each
other by only the last base.
4. There are three stop codons. They are UAA, UAG, and
UGA.
5. The genetic code is universal. It exists in prokaryotes and
eukaryotes and even viruses.
6. There is one start codon, AUG. It signals the start of
translation.
7. The AUG codon also codes for the incorporation of the
aminoacid methionine.
8. The region between the start and the stop codons is called
the coding region or the Open Reading Frame (ORF).
*A-Answer
Note –Please provide keywords, short answer, specific terms, specific examples (wherever necessary)
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