CBSE(NCERT) GRADE 12 BIOLOGY 2022 SET2

Lactic Acid Bacteria (LAB) sets milk into curd and also plays a very beneficial role for human health. Give any two suitable reasons.

(a) A person suffering from AIDS dies of opportunistic infections (ARC) i.e., infections that could have been otherwise overcome. (i) (ii) Give the scientific name of one bacterium and one parasite which mainly attack a person suffering from AIDS. (iii) Write the full form of the name of the widely used diagnostic test for AIDS.

(b) In spite of the statutory warning on cigarette packets against prevalent in the society. Enumerate four important health hazards to a smoker.

Though filariasis is not fatal, but the disease in humans is responsible for considerable suffering, gross deformities and disability. Write the scientific name of any two helminth worms causing the disease and state two chronic manifestations of filariasis.

Write any two anatomical features of xerophytic leaves that help them survive in xeric conditions.

State two morphological attributes observed in the leaves of desert plants that enable them to survive in extreme conditions in the desert.

By observing the bio-gas plant and the diagrams given below, answer the following questions: Which part of the above biogas plant is used as a source for the production of gaseous fuel and electricity? Explain giving reason.

Study the given diagrams of Biogas plants and answer the questions that follow: Which one of the two biogas plants can be used for generating gas fuel and electricity and why? Give suitable reasons in support of your answer.

(a) The following graphs (X) and (Y) show the annual variation of solar radiation reaching the Earth from January to December. Study them and answer the following questions: (i) Identify the graph that shows the (I) tropical region, and (II) temperate region (ii) Which of the regions (X) or (Y) shows greater biological diversity? Give two reasons.

(a) Study the given graphs (X) and (Y) depicting the annual variation in solar radiation on Earth from January to December and answer the undermentioned questions. (i) Identify the graph that depicts (I) tropical region, and (II) temperate region, respectively. (ii) Which of the two regions, (X) or (Y), will show high biological diversity and why? Give two reasons.

Over the last century, vaccination has been the most effective medical strategy to control infectious diseases. Explain the principle on which vaccination works.

(b) (i) How has the introduction of Nile Perch into Lake Victoria in East Africa had a devastating effect on the indigenous species in the lake? (ii) Name two invasive weed species which have posed a threat to the existence of our native species.

When Plasmodium sp. (malarial parasite) enters the human body, it reproduces asexually and increases its number. During this course, the affected person suffers from malaria. After a number of asexual cycles, the parasite, in order to complete its life cycle, enters the sexual phase of its life. Trace the sexual stages in the life cycle of Plasmodium in a female Anopheles mosquito, when it bites an infected person, up to the formation of mature infective stages of the parasite.

With the advent of sophisticated techniques of genetic engineering, we can now readily purify and isolate DNA. Name and explain the different steps involved in the separation and isolation of DNA fragments once cut by restriction endonucleases.

(i) When prickly pear cactus was introduced into Australia in early 1920s, it caused havoc and ecosystem instability by achieving very high population densities. Explain the reason for its rapid spread into millions of hectares of rangeland. (ii) Explain the importance of predator-prey relationship in a habitat.

(a) Draw a labelled diagram of a simple stirred-tank bioreactor. (b) State why a simple-stirred tank bioreactor generally has a curved base.

Given below is a picture of a natural large habitat that is being continuously broken into smaller patches. This process is continuing, increasing and expanding over time due to human impact, thereby posing a great risk to the existence of species in the habitat. (a) Do you agree with the above statement? Give two suitable reasons in support of your answer. (b) Write the ecological term used for such patches formed in an original habitat.

(a) Development of recombinant DNA technology has opened gates to many breakthroughs in the fields of medicine and agriculture. This has enabled scientists to isolate, sequence and manipulate individual genes obtained from diverse living or dead cells. Given below is a diagram showing the basic steps involved in genetically modifying an organism. Study the given diagram and answer the questions that follow : (i) Are two different types of restriction endonucleases used, one to cut the vector DNA and another to cut the desired DNA to be cloned? Support your answer, giving reason. (ii) Which enzyme is used at step (X) to integrate the foreign DNA with the vector DNA? (iii) What is the term used for step (Y) showing multiple copies of the foreign DNA being formed in transformed E. coli? (iv) Draw a diagram of E. coli cloning vector pBR322 to show the following : (I) Any one restriction endonuclease site in tetracycline resistance gene (II) Any one restriction endonuclease site in ampicillin resistance gene (III) (v) What does rop code for in plasmid pBR322 ?

Are two different types of restriction endonucleases used, one to cut the vector DNA and another to cut the desired DNA to be cloned? Support your answer, giving reason.

Which enzyme is used at step (X) to integrate the foreign DNA with the vector DNA?

What is the term used for step (Y) showing multiple copies of the foreign DNA being formed in transformed $E. coli$?

Draw a diagram of $E. coli$ cloning vector pBR322 to show the following: (I) Any one restriction endonuclease site in tetracycline resistance gene (II) Any one restriction endonuclease site in ampicillin resistance gene (III)

What does rop code for in plasmid pBR322?

(b) RNA interference (RNAi) holds great potential as a therapeutic agent for the treatment of human diseases and as a biocontrol agent for controlling pests in the agricultural fields. An experiment was performed to study the effect of RNAi in reducing the level of cholesterol in human primates with genetic disorders of cholesterol metabolism. Some people possess genetic disorders, which lead to the increase in the concentration of lipoproteins and lower the blood cholesterol. Tracy Zimmerman and her colleagues used RNAi in 2006 to reduce the cholesterol levels in non-human primates Cynomolgus monkeys. (i) One group of monkeys were given RNAi treatment (Small interfering RNAs, SiRNAs) (doses 1 mg/kg SiRNAs), (ii) Second group of monkeys were given RNAi treatment (doses 2.5 mg/kg SiRNAs), and (iii) Third group of monkeys were injected saline as control. The results of the experiments are illustrated in the graph given below:

(i) What do you interpret from the bars (X and Z) obtained after 264 hours of treatment of monkeys with saline and 2.5 mg/kg SiRNAs treatment? (ii) Name the category of organisms in the living world, where RNA interference (RNAi) takes place. Why? (iii) What is the basic principle involved in RNA interference (RNAi) in silencing the preferred genes?

Given below is a diagram showing the basic steps involved in genetically modifying an organism. Study the given diagram and answer the questions that follow: