Biology Sample Question Paper Sheet - Class Xii, Central Board Of Secondary Education, 2010 Page 36
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3922.
(i)
1.
Template strand
2.
Promoter
½ x 4 = 2
3.
Coding strand
4.
Terminator
(ii)
Coding strand because both mRNA and the coding strand are complementary to template
strand.
1
23.
(i)
In a closed flask containing NH
, CH
, H
and Water Vapour to simulate primitive atmosphere
3
4
2
(ii)
Electric discharge to simulate on primitive earth
(iii)
Formation of compounds like amino acids from simple molecules like NH
, CH
, H
1x 3
3
4
2
24.
a.
HIV enters the macrophage (human cell)
b.
Viral RNA genome replicates into DNA with the help of reverse transscription
c.
Viral DNA is incorporated into host DNA
d.
Viral DNA directs infected cell to produce viral particles
e.
Virus comes out while infected cell continues producing HIV particles
f.
New HIV particles infect Helper T cells which lead to decrease in Helper T cells.
½ x 6
25.
(a)
Masses of aerobic bacteria associated with fungal filaments
(b)
While growing they consume large amount of o
rganic matter of the effluents reducing BOD
?
(c)
When effluent goes to settling tank and flocs are allowed to sediment for activated sludge,
they get digested by anaerobic bacteria
1 + 1 + 1
26.
(a)
Isolate Nematode specific genes
(b)
Produces sense and antisense RNA in the host cells
(c)
Being complementary sense and antisense RNA form double stranded RNA (ds RNA)
(d)
Silence the specific mRNA of the Nematode
(e)
Parasite cannot survive in the transgenic tobacco host expressing RNAi
(f)
Thus the transgenic plant tobacco is protected from nematode
26.
A.
(i)
Insertional activation : A recombinant DNA is inserted within the coding sequence of
an enzyme -galactosidase, results in inactivation of the enzyme
(ii)
The bacterial colonies whose plasmids donot have the insert produce blue colour but
those with an insert do not produce colour
B.
Simple and easier method of selecting recombinants from non-recombinants.
27.
(a)
Palindromic nucleotide sequence / Recognition sequence.
(b)
DNA fragments from two different molecules which have the same kind of sticky ends
overhanging chains can be joined together (end to end) by DNA ligases.
1 x 3
(c)
EcoRI
28.
1.
Changing of all buses to run on CNG
a.
CNG burns most efficiently
36
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