lining the respiratory, gastrointestinal and urinogenital
tracts trap microbes entering our body.
(ii) Physiological barriers : Acid in the stomach, saliva in the
mouth, tears from eyes – all prevent microbial growth.
(iii) Cytokine barriers : Virus-infected cells secrete proteins
called interferons which protect non-infected cell, from
further viral infection.- ADA enzyme is crucial for the functioning of immune
system. ADA deficiency can lead to severe combined
immune deficiency (SCID). This disorder is caused due to
the deletion of the gene for adenosine deaminase. As a
first step, lymphocytes from the bone marrow of the patient
are grown in a culture outside the body. A functional ADA,
cDNA is introduced into these lymphocytes which are
subsequently returned to the patient. As these cells are
not immortal, the patient requires periodic infusion of such
genetically engineered lymphocytes. - (a) P and Q represent antibiotic resistant genes. These are
considered useful for selectable markers.
(b) T represents restriction site of (FRRI.
(c) S represents URS genes involved in the replication of plasmid. - The three methods which force ‘alien’ or recombinant DNA
into host cells are: electroporation, CaCl 2 treatment and
microinjection.
Electroporation : In this method, electrical impulses induce
transient pores in the host cell membrane through which
the DNA molecules are incorporated into the host cells.
CaCl 2 treatment: Treating cells with a specific concentration
of divalent cations, such as calcium cell increases the
efficiency with which DNA enters the cell through pores in
its cell wall. Recombinant DNA (UDNA) can then be forced
into such cells by incubating the cells with recombinant
DNA on ice, followed by placing them briefly at 42°C (heat
shock), and then putting them back on ice. This enables the
cells to take up the recombinant DNA.
(^) Microinjection : It is the introduction of foreign gene into plant
cell or animal cell by using microneedles or micropipettes.
- The density of a population in a given habitat during a given
period fluctuates due to changes in four basic processes :
(i) Natality - It refers to the number of births during a
given period in the population.
(ii) Mortality - It refers to the number of deaths in the
population during a given period.
(iii) Immigration - It refers to the number of individuals of
the same species that have come into the habitat from
elsewhere during a time period under consideration.
(iv) Emigration - It refers to the number of individuals of the
population who left the habitat and went elsewhere
during a time period.
23. (a) (i) It was necessary and a very effective step taken
by the local Government to switch over the entire fleet of
public transport to compressed natural gas (CNG) as CNG
causes less pollution in comparison to petrol or diesel.
(ii) Compulsory regular checkup of pollution emission by
vehicles also add to reduction in vehicular air pollution.
(b) (i) Use of unleaded petrol, low-sulphur petrol/diesel must
be insisted.
(ii) More use of public transport instead of private transport.
(c) The two values that the programme will inculcate in the
people of locality are:
(i) Cooperation and sharing of vehicles to reduce vehicular
air pollution, HJ, car pooling.
(ii) Awareness about the extent of environmental pollution
by automobiles.
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