Biology Abroad (Set 1) 2018-2019 Science (English Medium) Class 12 Question Paper Solution

State from where do the signals for parturition originate in human females.

Name the pattern of inheritance where F₁ phenotype

resembles only one of the two parents.

Name the pattern of inheritance where F₁ phenotype

does not resemble either of the two parents and is in between the two.

According to the Hardy-Weinberg principle, the allele frequency of a population remains constant. How do you interpret the change of frequency of alleles in a population?

Coelacanth was caught in South Africa. State the significance of the discovery of Coelacanth in the evolutionary history of vertebrates.

State the functions of mast cells in allergy response.

State the function of interpherons.

What is the cell that receives a recombinant gene called?

Name a disorder a human suffers from as a result of the monosomy of the sex chromosome. Give the karyotype and write the symptoms.

In the T.S. of a mature anther given below, identify "a" and "b" and mention their functions.

What is cleistogamy? Write one advantage and one disadvantage of it, to the plant.

State the role of the thymus as a lymphoid organ. Name the cells that are released from it and mention their function.

"Artificial insemination helps overcome several problems of normal mating in cattle". Do you agree? Support your answer with any three reasons.

Name and explain the interaction that is seen between clownfish and sea anemones.

Write the relationship between productivity, gross primary productivity, net primary productivity, and secondary productivity.

Justify the need for the signing of the 'Montreal Protocol' by the participating nations in 1987.

Emasculation and bagging are the two important steps carried during artificial hybridization to obtain superior varieties of desired plants. Explain giving reasons, in which types of flowers and at what stages are the two processes carried out.

State what is apomixis. Write its significance. How can it be commercially used?

Draw a sectional view of the human ovary. Label the following parts :

Name the hormones influencing the follicular development of corpus luteum.

Write the function of the following :
Micropyle

Given below is the representation of a relevant part of the amino acid composition of the β-chain of hemoglobin, related to the shape of human red blood cells.

(a) Is this representation of the sequence of amino acids indicating a normal human or a sufferer from certain blood related genetic diseases? Give reasons in support of your answer.

(b) Why is the disease referred to as a Mendelian disorder? Explain.

Name the kind of diseases/disorders and any two symptoms that are likely to occur in humans if Mutation in the gene that codes for an enzyme phenylalanine hydroxylase occurs.

Name the kind of diseases/disorders and any two symptoms that are likely to occur in humans if The karyotype is XXY

Name the technique and the property of plant cells that can help to grow somaclones of certain desired varieties of apple. Explain how somaclones of apple can be obtained in the lab so as to get the desired variety on a large scale.

Study the graph given below and answer the question that follows:

(i) The curve 'b' is described by the following equation :

`"dN"/"dt" = "r""N" {"K-N"/"K"}`
What does 'K' stand for in this equation? Mention its significance.

(ii) Which one of the two curves is considered a more realistic one for most of the animal populations?

(iii) Which curve would depict the population of a species of deer if there are no predators in the habitat? Why is it so?

"A very small sample of tissue or even a drop of blood can help determine paternity." Provide a scientific explanation to substantiate how it is possible.

Explain the phenomena of dominance, multiple allelism and co-dominance taking human ABO blood group as an example.

Name the genus to which baculoviruses belong. Describe their role in integrated pest management programmes.

Give a reason why :
DNA cannot pass into a host cell through the cell membrane.

Give a reason why :
Proteases are added during the isolation of DNA for genetic engineering.

Give a reason why :
Single cloning site is preferred in a vector.

State the medicinal value and the bioactive molecules produced by Penicillium notatum.

State the medicinal value and the bioactive molecules produced by Monascus purpureus.

State the medicinal value and the bioactive molecules produced by Trichoderma polysporum.

Describe the role of high temperature.

Describe the role of primers.

Describe the role of bacterium Thermus aquaticus in carrying the process of polymerase chain reaction.

How does the β-galactosidase coding sequence act as a selectable marker? Why is it a preferred selectable marker to antibiotic resistance genes? Explain.

Answer the following question based on Meselson and Stahl's experiment on E. coli :

Write the name of the chemical substance used as the only source of nitrogen in the experiment.

Answer the following question based on Meselson and Stahl's experiment on E. coli :

Why did they allow the synthesis of the light and the heavy DNA molecules in the organism?

Answer the following question based on Meselson and Stahl's experiment on E. coli :

How did they distinguish the heavy DNA molecules from the light DNA molecules? Explain.

Answer the following question based on Meselson and Stahl's experiment on E. coli :

Write the conclusion the scientists arrived at, at the end of the experiment.

Describe the process of megasporogenesis up to fully developed embryo sac formation in an angiosperm.

Given below is the diagram of a human ovum surrounded by a few sperms. Study the diagram and answer the following questions :

(a) Which one of the sperms would reach the ovum earlier?
(b) Identify 'D' and 'E'. Mention the role of 'E'.
(c) Mention what helps the entry of sperm into the ovum and write the changes occurring in the ovum during the process.
(d) Name the specific region in the female reproductive system where the event represented in the diagram takes place.

Study the schematic representation of the genes involved in the lac operon given below and answer the questions that follow :

(a) Identify and name the regulatory gene in this operon. Explain its role in 'switching off' the operon.

(b) Why is the lac operon's regulation referred to as negative regulation?

(c) Name the inducer molecule and the products of the genes 'z' and 'y' of the operon. Write the functions of these gene products.

How does the Hardy-Wienberg equation explain genetic equilibrium?

Describe how this equilibrium is disturbed that may lead to the founder effect.

Study the flow chart given below and complete the equation that follows by identifying 1, 2, 3 and 4.

N_{t + 1} = N_t + {(1+ 2) − (3 + 4)}

Mention the different ways by which the population density of different species can be measured.

'The pyramid of energy is always upright.' Explain

Explain with the help of labelled diagrams, the difference between an upright pyramid of biomass and an inverted pyramid of biomass.