AHSEC| CLASS 12| BIOLOGY| SOLVED PAPER - 2020| H.S. 2ND YEAR
2020
BIOLOGY
(Theory)
Full Marks: 70
Pass Marks: 21
Time: Three hours
The figures in the margin indicate
full marks for the questions
PART-I
(BOTANY)
MARKS
- 35
PART-II
(ZOOLOGY)
MARKS
- 35
Part - I (Botany)
1. What do you mean by Bt? 1
Ans:- The
full form of BT is Bacillus Thuringiensis. Bt crops are transgenic crops that
have been genetically engineered from the DNA of the bacterium Bacillus
thuringiensis. Bacillus thuringiensis in plant cells, thereby protecting crops from
pests.
2. What is conidia? 1
Ans:- Conidia
are asexual, immobile spores of a fungus. Asexual reproduction in ascomycetes
occurs by the process of formation of conidia which are borne on specialized
stalks commonly called conidiophores.
3. Give an example of endomycorrhiza. 1
Ans:- Endomycorrhizae
are more closely related to plant roots, where most plants such as crops,
greenhouse plants such as fruits, vegetables all contain endomycorrhizae.
4. What is gene pool? 1
Ans:- The
gene pool is the sum of all the genes and their alleles in a population. It is
also called the total genetic diversity found within a population or species.
5. Write on adaptation of xerophytes. 2
Ans:- Morphological
adaptations in xerophytic plants are: The stems of woody xerophytes are
comparatively short, hard and tough and covered with thick bark. Example:
Acacia Arabica. The main stem and branches can be thick, fleshy, flat and contain
green modified structures called phylloxera.
6. How plant tissue culture has helped
in improvement of crops? 2
Ans:- Growing
cells or tissues or organs on a nutrient medium to produce new plants in
laboratories under in vitro conditions is called tissue culture. It mainly
depends on the principle of totipotency. Tissue culture has been used to create
genetic variability that can improve crop plants, improve the health status of
planting material, and increase the number of desirable germplasm available to
plant breeders. Can do. Tissue culture techniques have been used successfully
in combination with molecular techniques to induce specific traits through gene
transfer.
7. How is insulin produced through genetic
engineering? 2
Ans:- Genetic Engineering Process: The gene for human insulin is inserted into the gap of the plasmid.
This plasmid is now genetically modified. The genetically modified plasmid is
inserted into a new bacterial or yeast cell. Then this cell divides rapidly and
starts producing insulin.
Or
What is palindrome? Give an example of palindromic sequence.
Ans:- Palindromic sequence is a nucleic
acid sequence on double-stranded DNA or RNA in which a 5' to 3' forward reading
sequence on one strand matches a 5' to 3' reverse reading sequence on the
complementary strand with which it forms a double helix.
A strand is called a palindromic sequence if the sequence of
nucleotides is the same as its complement. Like ACCTAGGT is a palindrome. The
complementary strand will contain TGGATCCA and if reversed it will be identical
to the original sequence.
8. What is triple fusion? Write the
significance of it. 2
Ans:- The
fusion of the male gamete with the diploid secondary nucleus/central cell to
form a triploid primary endosperm nucleus is called triploid fusion because it
involves three nuclei.
Triple fusion results in the formation of a triploid nucleus which
is called the primary endosperm nucleus. This nucleus gives rise to the
formation of endosperm by repeated mitotic divisions. This endosperm provides
nutrition to the developing embryo.
Or
Write briefly on artificial vegetative reproduction in plants.
Ans:- Methods of Artificial Vegetative Propagation
– Cutting (by cutting the stem) Common methods of artificial vegetative
propagation are cutting, grafting, budding and layering. Cutting involves
removing a portion of the stem and burying it in soil to allow growth of roots
and bud germination.
9. What is cellular totipotency? What is
the importance of it in plant science? 2
Ans:- Cellular
totipotency is the ability of a single cell to produce all types of cells and
organize them into an entire organism when cultured in an appropriate culture
medium at appropriate temperature and aeration conditions. Spores and zygotes
are examples of totipotent cells.
Totipotency is the ability of a plant cell to give rise to an entire
new plant. Plant cells are powerful cells. This ability of plant cells allows
them to be used for plant propagation and improvement.
10. Explain briefly? (any two) 2+2=4
(i) Genetic therapy
Ans:- Gene therapy is a technique that involves
replacing defective genes with healthy genes to treat genetic disorders. It is
an artificial method that allows the entry of DNA into the cells of the human
body.
(ii) PCR
Ans:- Polymerase chain reaction or PCR
is a reaction used to amplify a gene or fragment of DNA of interest. This is
done in vitro using primers. This technology is used in laboratories to create
billions of copies of a desired gene for research, diagnostic, and therapeutic
purposes.
(iii) Endonuclease.
Ans:- Endonucleases are enzymes that
produce internal cuts in DNA molecules. Many endonucleases break DNA molecules
at random locations, but there is a class of endonucleases that break DNA only
within or near sites that contain specific base sequences.
11. Write the scientific names with
utilities of the following plants: (any three) (0.5+0.5)x3=3
(a) Teak
Ans:- One such interesting plant is
Tectona grandis L.f. (TG). It belongs to the Verbenaceae family. It is commonly
called teak. It is a large deciduous tree and can reach a height of 30–40
meters with flutes and buttresses found at the base of older trees.
(b) Jute
Ans:- The botanical name of jute is
Corchorus (genus). The botanical name of the species used in making sacks and
bags is Corchorus olitorius.
(c) Cinchona
Ans:- Cinchona L. Species: Cinchona
officinalis L. Cinchona or Peruvian bark contains the alkaloid compound
quinine, which is an effective treatment for the deadly disease malaria.
(d) Tea
Ans:- Camellia sinensis is a species of
evergreen shrub or small tree in the flowering plant family Theaceae. Its
leaves and buds are used to make black and green tea.
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