Q29 of 30 Page 1

Describe the mechanism of pattern of inheritance of ABO blood groups in humans.

OR


(a) Why is haemophilia generally observed in human males? Explain the conditions under which a human female can be haemophilic.


(b) A pregnant human female was advised to undergo M.T.P. It was diagnosed by her doctor that the foetus she is carrying has developed from a zygote formed by an XX-egg fertilized by Y-carrying sperm. Why was she advised to undergo M.T.P.?


Inheritance of ABO blood group in humans follows the process of Co-dominance thus both the alleles are expressed in the progeny.

For blood grouping there type of alleles are present namely IA , IB , i or IO.


The presence of types of alleles in genes tells about the type of antigen and antibody present in body thereby leading to speciation of blood groups.


• If IA i or IA IA are present then it is blood group A


• If IB i or IB IB are present then it is blood group B


• If IA IB or IB IA are present then it is blood group AB


• If i i are present then it is blood group O



OR


a) Haemophilia is generally observed in human males as it is X-linked recessive disease.


Since human males have genetic makeup of XY thus it would only require a single X chromosome with abnormal haemophilia gene on it to express itself in the form of a disease.


Females having genetic makeup of XX are both carriers as well as may show up as a disease.


If only one X chromosome has the defective Haemophilia gene then the female is a carrier and if both chromosomes have defective haemophilia gene then the female is diseased.


b)The pregnant female was advised MTP ( Medical Termination Of Pregnancy) because the doctor diagnosed her foetus to be suffering from Klinefelter’s syndrome having the genetic makeup of 44+XXY.


Once the child grows he would be suffering with various symptoms like muscle weakness, decreased libido, absent or incomplete puberty, decreased sexual maturity, gynaecomastia, weak bones, increased belly, etc.


Thereby to prevent the child to suffer from such devastating symptoms the doctor advised the termination of pregnancy.


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26

Water is very essential for life. Write any three features both for plants and animals which enable them to survive in water scarce environment.

OR


How do organisms cope with stressful external environmental conditions which are localised or of short duration?


 27

(i) State the consequence if the electrostatic precipitator of a thermal plant fails to function.

(ii) Mention any four methods by which the vehicular air pollution can be controlled.


 28

Give reasons why:

(i) Most zygotes in angiosperms divide only after certain amount of endosperm is formed.


(ii) Groundnut seeds are exalbuminous and castor seeds are albuminous.


(iii) Micropyle remains as a small pore in the seed coat of a seed.


(iv) Integuments of an ovule harden and the water content is highly reduced, as the seed matures.


(v) apple and cashew are not called true fruits.


OR


(a) Draw a labelled diagram of L.S. of an embryo of grass (any six labels).


(b) Give reason for each of the following:


(i) Anthers of angiosperm flowers are described as dithecous.


(ii) Hybrid seeds have to be produced year after year.


 30

(i) Describe the characteristics a cloning vector must possess.

(ii) Why DNA cannot pass through the cell membrane? Explain. How is a bacterial cell made ‘competent’ to take up recombinant DNA from the medium?


OR


If a desired gene is identified in an organism for some experiments, explain the process of the following:


(i) Cutting this desired gene at specific location.


(ii) synthesis of multiple copies of this desired gene.