They act as substrates i.e., nucleotides for the replication
process as well as provide energy for the polymerisation of
nucleotides by cleavage of high energy terminal phosphate
bonds.- (a) Dryopithecus was apelike primate about 15 mya.
(b) Australopithecus lived in East African grasslands about 2 mya.
- Proinsulin has three polypeptide chains (A, B and C) which
need to be processed before it becomes fully mature and
functional insulin. C peptide chain is removed during
maturation of insulin and has only two polypeptide chains
i.e., A-chain and B-chain joined by disulphide bond are
present in mature insulin. - Chikungunya and dengue can be controlled by the
eradication of Aedes mosquitoes. - In the town of Arcata situated along the Northern Coast
of California, an integrated waste water treatment process
was developed with the help of biologist from Humboldt
State University. Waste water is treated in the following
manner :
(i) Waste water is filtered to remove floating and large
suspended solids.
(ii) Precipitated solids (sediments) are removed in the next
step.
(iii) The clear water is now chlorinated with chlorine or
perchlorate salt.
This treated water contains lots of heavy metals and
other dangerous pollutants.
(iv) In this step, a series of six connected marshes in 60
hectares of marshland seeded with bacteria, algae, fungi
and plants, which absorb, assimilate and neutralise the
pollutants. The naturally purified water is the then allowed
to flow out. - (a) Azotobacter and Azospirillum.
(b) Leguminous crops have symbiotic nitrogen fixing bacteria
such as Rhizobium that live in the root nodules of these
plants. These bacteria obtain food and shelter from the
plant and in return they trap nitrogen directly from the
atmosphere which they provide to the plant.
- The retention of the desired characteristics repeatedly in
the future generations of the tomato crop can be done by
micropropagation which is a type of vegetative propagation.
This procedure helps in rapid multiplication of plant in a
short period of time and in less space. - (a) Heroin is obtained from the poppy plant (Papaver
somniferum). It is obtained by acetylation of morphine
which is extracted from the latex of poppy plant.
(b) Some of the effects of heroin on the human body are as
follows :
(i) It is a depressant and slows down body functions It
also induces drowsiness and lethargy.
(ii) Other effects include indigestion, reduced vision, decreased
weight, sterility and total loss of interest in work.- In a given population one can find out the frequency of
occurrence of alleles of a gene or a locus. This frequency
is supposed to remain fixed and even remain the same
through generations. Hardy-Weinberg principle stated
it using algebraic equations which says that allele
frequencies in a population are stable and is constant
from generation to generation. The gene pool i.e., total
genes and their alleles in a population remains constant.
This is called genetic equilibrium. Sum total of all the allelic
frequencies is 1. Individual frequencies, for example, can be
named ‘p’, ‘q’, etc. In a diploid, ‘p’ and ‘q’ represent the
frequency of allele ‘A’ and allele ‘a’. The frequency of ‘AA’
individuals in a population is simply p^2. This is simply stated
in another ways, i.e., the probability that an allele A with
a frequency of ‘p’ appear on both the chromosomes of a
diploid individual is simply the product of the probabilities,
i.e., ‘p^2 ’. Similarly of ‘aa’ is ‘q^2 ’, of ‘Aa’ ‘2pq’. Hence, p^2 +
2pq + q^2 = 1. This is a binomial expansion of (p + q)^2.
When the measured frequency differs from expected values,
the difference (direction) indicates the extent of evolutionary
change. Disturbance in genetic equilibrium, or Hardy-Weinberg
equilibrium, i.e., change of frequency of alleles in a population
would then be interpreted as resulting in evolution.
OR
In prokaryotes, DNA lies in the cytoplasm which is
supercoiled (coiled and recoiled) with the help of RNAs
and non-histone basic proteins like polyamines. DNA being
negatively charged is held in place with the help of these
proteins that have positive charges in a region termed as
nucleoid. The DNA in nucleoid is organised in large loops
held by proteins. - (a) Differences between analogous and homologous
structures are as follows :
Analogous structures Homologous structures
(i) They show superficial
resemblance but their
internal structure is
quite different.
They differ morphologically
but they have similar
internal structure.(ii) They develop in
unrelated organisms.They develop in related
organisms.
(iii)They have similar
functions.They perform different
functions.
(iv)Analogous organs show
convergent evolution.Homologous organs
show adaptive radiation
(divergent evolution).
(v) Example : Stings of
honey bee and scorpion.Example : Vertebrate
forelimbs.