CBSE(NCERT) GRADE 12 BIOLOGY 2023 SET2

Three genes R, S and T are located on the same chromosome. If the recombinant percentage between R and S is 20%, R and T is 35% and S and T is 15% respectively, can you predict the correct order of these genes on the chromosome? Which of the following shows the correct sequence of the genes on the chromosome?

The graph plotted below is based on the data collected by biology students with respect to the levels of oxygen at the specific points in the river flowing outside their city. Which point in the graph indicates the entry of untreated sewage in the river?

Identify the region, factor and enzyme in the process of transcription in prokaryote as shown in the schematic representation given below. Region Factor Y Enzyme Z

The status of the human population reflected in the human age pyramid given below is:

Which one of the following products was produced as a result of DNA?

Select the option that gives the correct description of the process of Natural Selection with respect to the length of the neck of giraffe.

Study the DNA profiles obtained as a result of DNA fingerprinting of a child and three individuals 1, 2 and 3. Which option shows the possible parentage?

Choose the option that gives the correct number of pollen grains that will be formed after 325 microspore mother cells undergo microsporogenesis.

Given below are the steps carried out to construct a recombinant DNA. Which one of the following gives the correct sequence of these steps?

Given below are the steps carried out to construct a recombinant DNA. Which one of the following gives the correct sequence of these steps? (i) Isolation of genetic material (ii) Insertion of recombinant DNA in the host cell / organism (iii) Obtaining the foreign gene product (iv) Amplification of gene of interest (v) Downstream processing

After the completion of biosynthetic stage in a bioreactor, the product undergoes a series of processes before it is ready for marketing. List of the processes is given below. Identify the option that gives the correct sequence of the processes carried out: (i) Purification of product (ii) Formulation with suitable preservative (iii) Separation of product (iv) Clinical trial of product

For Questions number 13 to 16, two statements are given one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below. (a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A). (b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A). (c) Assertion (A) is true, but Reason (R) is false. (d) Assertion (A) is false, but Reason (R) is true. Assertion (A): Crystal protein Bt toxin does not kill the Bacillus but kills the insects. Reason (R): Bt toxin exists in inactive form in Bacillus but when ingested by the insect, the acidic pH of its gut changes it into an active form.

Assertion (A): Endosperm is completely consumed during the development of embryo in ex-albuminous seeds. Reason (R): Castor, pea and beans are all examples of ex-albuminous seeds.

Assertion (A): In an operon, the regulator and operator genes are not associated with the constitutive genes. Reason (R): Constitutive genes need not be repressed.

Assertion (A): Cattle and goats are never seen browsing on Calotropis growing in abandoned fields. Reason (R): Cattle and goats avoid grazing on Calotropis because of the offensive smell of its flowers.

From which end of the ovule, and how does the pollen tube gain its entry into the embryo sac of a Hibiscus flower?

State the fate of the male nuclei present in the pollen tube.

India is the seventh largest country in the world in terms of total land area including land and water. Write the value of the land area of our country (in terms of percentage) of the world. Mention then, what makes India one of the 12 mega diversity countries of the world.

Vectors are DNA molecules that can carry a foreign DNA segment into the host cell.

Give one example each of vectors used for cloning genes in plants and animals.

Plants capture only 2 10 percent of the photosynthetically active radiation of the Sun and this small amount of energy is able to sustain the entire living world. During this process, ecosystems are in consonance with the two laws of thermodynamics. Explain.

Write how can an alien DNA be introduced into (i) an animal cell (ii) a plant cell.

The diagram given below shows a developmental stage of human embryo. Answer the following questions with reference to it: (a) Identify and name the human embryonic stage shown. (b) Mention its exact location in the normal pregnancy of a woman. (c) Write one function of each of the .

(a) Name the two primate ancestors of the present day humans, who existed approximately about 15 million years ago. (b) According to geological records, when and where did Australopithecines live? (c) Give two differences between Homo habilis and Homo erectus.

(a) Differentiate between malignant and benign tumours. (b) Name and explain the most feared property of a malignant tumour.

Name the two primate ancestors of the present day humans, who existed approximately about 15 million years ago.

With the help of a schematic diagram only, show in three steps, the formation of recombinant DNA by the action of restriction endonuclease EcoRI and DNA ligase.

According to geological records, when and where did Australopithecines live?

(a) (i) Expand the abbreviations given below, used for different modes of assisted reproductive technologies: (1) ZIFT (2) ICSI (3) IUT (4) GIFT (ii) Which one of them cannot be considered as a procedure of IVF? Give reasons in support of your answer. OR (b) Differentiate between the following: (i) Perisperm and Pericarp (ii) Syncarpous pistil and Apocarpous pistil (iii) Plumule and Radicle

Give two differences between Homo habilis and Homo erectus.

(a) . (b) From where can one obtain in humans ? (c) State any two applications of stem cells in curing human diseases.

Treatment of wastewater is done in a sewage treatment plant to make it less polluting. Explain the following with reference to this treatment process: (a) Primary sludge (b) Activated sludge (c) Anaerobic sludge digesters

Study the pedigree chart given below and answer the questions that follow: (i) Is this trait recessive or dominant? Give reason. (ii) Is this trait sex-linked or autosomal? Give reason. (iii) Among individuals 3, 4 and 7, which one is homozygous for the trait?

A schematic representation of Earth's regions has been given below in which chromosomes and by which answer the following questions: (a) When moving from region to region, note the variability in species and give two reasons. (b) Mention the estimated number of bird species found in India. OR (b) Name the region of the world where maximum biodiversity is found.

Why is the regulator gene in lac ?

Draw a schematic diagram of lac operon in absence of inducer in the culture medium of the bacteria.

When and how does foetal ejection reflex begin ?

Pituitary gland and uterine muscles play an important role during parturition. Explain.

A functional mammary gland is a characteristic of all female mammals. Given below is a diagrammatic sectional view of a mammary gland. Identify the parts 1, 2 and 3, and mention one function of each of them.

How are the characteristic features of pollen, anther and stigma of a maize plant suited for pollination by wind ?

How do you justify that : (1) Pollen grains are recovered from fossils ? (2) Micropyle remains as a small pore in the seed coat of a fully developed seed ?

A time-bound vaccination programme is followed for the children in our country from their birth up to ten years of age. A graph plotted below shows the effect of the vaccination followed by infection by the same pathogen, and the antibody concentration in the blood of the child.

Explain why the administration of a vaccine

Explain why the administration of a vaccine causes an increase in the antibody concentration.

Why is the consumption of smack considered as an abuse ?

Name the source plant and one effect of the following drugs on the human body: (1) Marijuana (2) Cocaine (3) Morphine

Which two types of nitrogen were used by them in their experiment and why ?

Why did they take samples of E. coli at definite time intervals for their observation ?

State the role of caesium chloride density gradient in their experiment.

Write the conclusions they arrived at.

A true breeding tall pea plant with round seeds is crossed with a recessive dwarf pea plant having wrinkled seeds. Work out the cross up to $F_2$ generation giving the phenotypic ratios of $F_1$ and $F_2$ generation respectively.

State the Mendelian principle that can be derived only with the help of such a cross.