UNIT TEST
TOPIC: MOLECULAR BASIS
OF INHERITANCE
MARKS:-25 TIME:-1.30HRS.
SECTION-A
QN.1) SELECT AND WRITE THE CORRECT ANSWER: - (04)
i)
The terminator codons are
a) UAA, UAG, UGA b) AUG, UAG,
UGA
c)
UAC, AUG, UAG d)
DCC, UAA, CAC
ii) The
main step involved in the process of translation is
a) Activation of amino acid
b)
Initiation of polypeptide chain synthesis
c)
Termination of polypeptide chain formation
d)
Transfer of polypeptide chain to tRNA
iii) Exons
help in synthesis of
a) Proteins b) fatty
acids
c)
Fats d) glycogen
iv) The
octamer core of nucleosome contains two molecules each of the following
histones
a) H2A, H2B, H3 and H4
b)
H1, H2A, H2B, H3
c)
H1, H2A, H2B, H4
d) H1, H2B, H3, H4
QN.2)
ANSWER THE FOLLOWING: - (03)
i) How many base pairs of DNA helix
are wound over on nucleosome approximately?
Ans:-Approximately
200 base pairs.
ii) Name the enzyme which nicks DNA strands
temporarily at point ‘O’.
Ans:-Enzyme
endonuclease
iii) What is the number of estimated base
pairs in the bacterium E.coli?
Ans:-4.6 million
base pairs.
SECTION-B
ATTEMPT ANY FOUR: - (08)
QN.3) Give any two
applications of genomics.
Ans: - 1) Used in agriculture to develop transgenic crops having
more desirable characters.
2) Genetic markers
developed in genomics have applications in forensic analysis.
3) Genomics can lead to
introduce new gene in microbes to produce enzymes, therapeutic proteins and
even biofuels.
4) Helps on treatment
of genetic disorders through gene therapy.
5) Improvement of
livestock is also possible.
QN.4) Give the
role of b-galactoside
permease and b-galactoside acetyltransferase.
Ans:-1) b-galactoside permease- permits lactose molecules to
enter into the cell.
2) b-galactoside acetyltransferase- transfers
acetyl group from acetyl CO-A to galactoside.
QN.5) Draw a well
labelled diagram of transcription unit.
QN.6) Identify ‘A’
and ‘B’ in the following figure,
QN.7) Differentiate between leading strand and lagging strand (any two
points).
|
Leading strand |
Lagging strand |
|
1) Continuously growing strand
is |
1) The
discontinuously growing |
|
2) Synthesis of leading
strand |
2) Synthesis
of lagging strand |
|
3) Only one RNA primer is
required. |
3) Large
number of RNA primers are required. |
|
4) Okazaki fragments are not |
4) Okazaki
fragments are produced. |
|
5) Activity of DNA ligase is
not |
5) Activity
of DNA ligase observed to join DNA
fragments |
|
6) Leading strand is synthesized over leading templet. |
6) Lagging
strand is synthesized over lagging templet. |
QN.8) Match the
following columns and write the correct answer,
|
Column(I) |
Column(II) |
|
|
i)
Leu |
|
|
ii)
Isoleu |
|
c)
AUU |
iii)
Phe |
|
d)
UUA |
iv)
Met |
SECTION-C
ATTEMPT ANY TWO: - (06)
QN.9) Explain any
three properties of genetic code.
Ans:-1) Genetic code is triplet code
2) Distinct polarity
3) Non-overlapping
4) Commaless
5) Degeneracy
6) Universal
7) Non-ambiguous
(FOR EXPLAINATION WATCH THE FULL VIDEO)
QN.10) Give an account of Hershey-Chase experiment that
proved, ’DNA is the genetic material’.
Ans: - 1) worked with
bacteriophages that composed of DNA and proteins.
2) Used radioactive phosphorus
32P in the medium for some viruses and radioactive sulphur 35S
for some others.
3) Viruses cultured on
medium with radioactive phosphorus contained radioactive DNA but not
radioactive protein because DNA contains phosphorus but proteins do not.
4) Similarly viruses
grown on radioactive sulphur contained radioactive protein but not radioactive
DNA because DNA does not contain sulphur.
5) These phages were
allowed to infect E.coli bacteria containing normal ‘P’ and ‘S’. After
infection viral coats were removed by centrifugation.
6) Bacteria
infected with viruses containing radioactive DNA were radioactive and those
infected with containing radioactive sulphur were not radioactive.
7) This
indicates that protein did not enter the bacteria. Hence, DNA is the genetic
material.
QN.11) State any three aims of human genome project.
Ans: - 1) Mapping the entire human genome at the level of nucleotide
sequence.
2) To store the
information collected from the project in databases.
3) To develop tools and
techniques for analysis of the data.
4) Transfer the related
technologies to the private sectors such as industries.
5) Taking care of the
legal, ethical and social issues which may arise from the project.
SECTION-D
ATTEMPT ANY ONE (04)
QN.12) Explain various steps of DNA fingerprinting in sequence. Draw a
flow sheet diagram for the same.
Ans:-Technique of DNA fingerprinting involves
following steps.
(A) Extraction of DNA:
DNA
molecule from sample is extracted which may be blood stain, semen, saliva, etc.
(B) Amplification:
Many
copies of DNA are made by polymerase chain reaction (PCR) if the content of DNA
is less.
(C) Restriction digestion / Fragmentation:
It
is cutting of DNA into fragments containing VNTRs at specific site with the
help of restriction endonucleases.
As
a result DNA fragments of different lengths are obtained which contain VNTR.
(D)
Electrophoresis:
1. Broken DNA fragments are separated and
arranged according to their
length and electric charge on ‘Agarose
polymer Gel slab’.
2. It is a method of separation of charged
molecules by applying electric field.
3. The DNA molecule have negative charge.
Therefore, they move towards anode.
4. The DNA fragments move through the gel column and the rate of
movement depends upon length of fragment.
E) Splitting or Conversion of ds-DNA:
By using alkaline
chemicals ds-DNA can be made single stranded.
(F) Southern Blotting (Development by Southern).
1. Transfer of separated DNA sequences from gel on nitrocellulose or
nylon membrane which shows number of ss-DNA fragments.
2. These fragments get permanently fixed on membrane.
3. ss-DNA fragments are hybridized with already available DNA probes
or markers (radiolabeled).
4. In autoradiography probe hybridizes with those ss-DNA strands which
contain VNTR.
5. This nylon membrane is exposed to x-ray film to mark the places
where DNA probe bound to DNA fragments.
6. The hybridized regions are marked as dark bands on x-ray film
called as autoradiograph which represents DNA fingerprint.
QN.13) Describe the
experiment that proves, ‘DNA replication is semiconservative’.
Ans: - 1) semiconservative nature of DNA replication was experimentally
proved by Messelson and Stahl using equilibrium density gradient centrifugation
technique.
2) Cultured E.coli
in the medium containing 14N (light nitrogen) and obtained
equilibrium density gradient band by using CsCl2.recorded position
of this band.
3) These cells were
transferred to 15N (heavy isotopic nitrogen) medium and allowed to
replicate for several generations.
At equilibrium
point density gradient bands were obtained and position was recorded.
4) Heavy DNA can be
distinguished from light DNA on the basis of density gradient.
5) Now these cells
were cultured on medium containing 14N (normal nitrogen). After
first generation density gradient band for 14N15N was
obtained and its position was recorded. Two such bands were obtained after
second generation, one at 14N and other at 15N position.
6) This clearly
proved that replication is semiconservative.
