ISC Biology 2017 Class-12 Previous Year Question Papers

In a marriage between Rh woman and Rh+ man, when a woman become pregnant, she becomes sensitive while carrying a first Rh+ child within her womb. It is because some of RBCs from the developing embryo get into the blood stream of mother during development causing her to produce anti-Rh-antibodies. The first child of such parents is normal and is delivered safely. However, if such a mother get pregnant again the resulting Rh+ foetuses will be exposed to anti-Rh-bodies produced by the mother.

As a result serious damage to RBCs of the developing embryo will occur causing erythroblastosis foetilis. The disease leads to the death of the developing embryo before birth or after parturition.

Question 9.
(a) Discuss the various In-situ and Ex-situ strategies for conservation of biodiversity. [4] (b) List any four applications of tissue culture. [4] (c) Mention the causative agent and the preventive measures for each of the following: [2] (i) Gonorrhoea
(ii) Pneumonia.
Answer:
(a) In-situ conservation is on-site conservation. It is carried out by
(i) Sacred groves
(ii) Sacred lakes
(iii) Protected areas-India has 89 National Parks, 492 Wildlife Sanctuaries and 13 Biosphere Reserves. The Protected Areas include terrestrial areas, wetlands and aquatic ecosystem.

National Afforestation Ecodevelopment Board (NAEB) looks after afforestation,
(i) tree planting, ecological restoration and ecodevelopment of the country,
(ii) Ex-situ conservation is also called off-site conservation. It is carried out by :

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(a) Botanical and zoological garden
(ii) Gene Banks- Seed gene banks and Field gene banks are maintaining germplasm of different plants and animals. Wildlife Safari Parks
(iii) Cryopreservation techniques to preserve eggs of threatened species,
(iv) Tissue culture technique for propagation of plants.

(b) Applications of tissue culture :
(i) Rapid clonal propagation – an explant is used to produce numerous plants of same genotype,
(ii) From somaclonal variation, a number of useful varieties have been produced, e.g., Higher shelf life tomato,
(iii) Virus free plants by using meristem culture,
(iv) Embryo which normally do not survive inside the seeds can be grown in tissue culture. Embryo rescue useful in interspecific hybridisation.

(c)

(i) Gonorrhoea : It is a STD caused by Diplococcus bacterium Neisseriagonorrhoeal. It is transmitted by sexual intimacy. It is prevented by :

  • avoiding sex with unknown partners,
  • Use condom during coitus
  • Consult qualified doctor for early detection and complete treatment.

(ii) Pneumonia : It is caused by Streptococcus or Diplococcus pneumoniae or Haemophilus influenzae. Disease is transmitted by droplet infections. The disease can be prevented by covering the mouth to prevent inhaling of droplets/aerosols when visiting an infected person, articles used by the patient should be properly sterlized. Proper disposal of the sputum of an infected person.

Question 10.
(a) Name the components of lac operon and discuss their role.
(b) Give the significance of transgenic animals.
(c) Give one significant difference between :
(i) Electroporation and Gene Gun.
(ii) ECG and EEG
Answer:
(a) The various components of lac operon are regulator gene, promoter gene, operator gene and structural genes. Regulatory genes synthesise a chemical called repressor which combine with operator gene to switch off the operon. In the presence of inducer – the lactose, repressor binds with lactose to free the operator gene and the operon is switch on. Promoter gene is the recognition site for RNA polymerase when the operon is switched on. The RNA polymerase pass over the operator gene and reach structural genes to transcribe them. Operator gene controls the expression of operon by switching on and off the structural genes transcribe polycistronic zn-RNA. Lac operon has three structural genes Z, Y and A. The polycistronic m-RNA produces three enzymes galactosidase permease (early of lactose into bacterium), β-galactosidase (breakage of lactose into glucose and galactosidase) and galactoside acetylase (transfer acetyl group to β-galactosidase).

Note : Inducer is a chemical generally a substrate binds with repressor to free the operator ‘ gene.

(b) Transgenic animals have great importance as
(i) to study the normal physiology and development, working of genes, their regulation etc.
(ii) study of diseases susceptibility to different diseases has been found to the genetically controlled, transgenic animals can be used to study how genes take part in the development of diseases,
(iii) By inserting genes for some important biological products specially milch animals, transgenic animals can be used for molecular farming or molecular harvesting, e.g., Protein a-1 anti trypsin for treating emphysema, lactoferrin (cow),
(iv) Vaccine safety testing on transgenic animals before marketing,
(v) Chemical safety testing,
(vi) Transgenic cattle with extra gene for growth hormone and caesin gives very high yield of milk. Transgenic cow Rosie yielded milk with high protein having human alpha lactalbumin a highly nutritionally balanced diet for human babies.

(c)

(i) Electroporation : A method for increasing DNA uptake by protoplast through prior exposure to high voltage which results in the temporary formation of small pore in cell membrane.

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Gene Gun : It is the vectorless transfer of gene where tungsten or gold particles coating with desired genes are bombarded into the cells with great force. ,

(ii) ECG (Electrocardiograph): Gives vital information about

  • rate and rhythm of heart beat
  • condition of heart muscle.

(iii) EEG (Electroencephalograph): Represents spontaneous electrical activity of brain. The shape of the waves varies considerably depending upon the degree of activities with in the brain itself.
Or
It is a device used for recording the generation and transmission of electrical impulses through the conductive tissue of heart muscles.

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