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Q3
long answer
2 marks
(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.
Solution
(i) The tropical region is represented by the graph showing nearly uniform solar radiation throughout the year, while the temperate region is represented by the graph showing large seasonal variation in solar radiation.
(ii) The tropical region will show higher biological diversity.
Reasons:
1. The tropical region receives more or less uniform and abundant solar energy throughout the year, so primary productivity remains high.
2. The stable, warm climate with little seasonal fluctuation allows many species to survive and specialize, leading to greater species richness and biodiversity.
Q6
short answer
2 marks
(ii) Which of the two regions, (X) or (Y), will show high biological diversity and why? Give two reasons.
Solution
The tropical region will show high biological diversity.
Reasons:
1. It receives relatively constant and high solar radiation throughout the year, resulting in high primary productivity.
2. The environment is stable with little seasonal variation, which supports more species and promotes speciation, leading to greater biodiversity.
Q6
short answer
2 marks
OR
(b) (i) When prickly pear cactus was introduced into Australia in early
Solution
The introduction of prickly pear cactus in Australia is an example of an alien invasive species becoming a serious weed. It spread rapidly because it had no natural enemies there, causing ecological and agricultural damage.
Q7
short answer
3 marks
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.
Solution
The separation and isolation of DNA fragments cut by restriction endonucleases involves the following steps:
1. Agarose gel electrophoresis: The DNA fragments are loaded into wells made in an agarose gel and an electric field is applied. Since DNA is negatively charged, it moves towards the positive electrode.
2. Separation by size: Smaller DNA fragments move faster and travel farther through the gel matrix, while larger fragments move more slowly. Thus, fragments are separated according to size.
3. Visualization: After electrophoresis, the DNA fragments are stained with ethidium bromide and observed under UV light as distinct bands.
4. Extraction/Isolation: The required DNA fragment is cut out from the gel and recovered by gel elution or similar methods.
Thus, agarose gel electrophoresis is used to separate the fragments, and the desired fragment is then isolated from the gel.
Q8
short answer
3 marks
(a) Development of recombinant DNA technology has made the production of vaccines possible in heterologous systems/bacteria or any other organism. Give an example of a vaccine developed by such a technology and the host used.
(b) Explain how a humoral immunity system gets into action when a foreign antigen enters into a human body.
Solution
(a) Example: Hepatitis B vaccine produced using genetically engineered yeast (Saccharomyces cerevisiae) as the host.
(b) When a foreign antigen enters the human body, it is recognized by antigen-presenting cells, which process and present it to helper T-cells. These activate B-lymphocytes, which proliferate and differentiate into plasma cells. The plasma cells secrete specific antibodies against the antigen. These antibodies neutralize the antigen and help in its elimination. Some B-cells also form memory cells for a rapid response on future exposure.
Q9
short answer
3 marks
(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.
Q10
short answer
3 marks
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.
Q11
short answer
3 marks
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.
Q11
short answer
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.
Q12
short answer
3 marks
An application of biotechnology in agriculture involves production of pest resistant crops using Bacillus thuringiensis.
(a) Proteins coded by which specific Bt toxin genes control corn borer ?
(b) How does Bt toxin produced by the bacteria kill the insect ? Explain.
Q12
short answer
Which enzyme is used at step (X) to integrate the foreign DNA with the vector DNA?
Q13
long answer
5 marks
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 ?
Q13
short answer
What is the term used for step (Y) showing multiple copies of the foreign DNA being formed in transformed $E. coli$?
Q14
short answer
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)
Q15
short answer
5 marks
What does rop code for in plasmid pBR322?
Reading Passage
RNA interference (RNAi) holds great potential as a therapeutic agent for the treatment of human diseases and as a bicontrol agent for controlling pests in the agricultural fields. An experiment was treatment of disorders of cholesterol metabolism. Some people possess genetic them to coronary artery diseases. lipoproteins and lower the blood cholesterol. Tracy Zimmerman and her colleagues used RNAi in 2006 to reduce -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 :
Q16
short answer
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?
Q17
short answer
Name the category of organisms in the living world, where RNA interference (RNAi) takes place. Why?
Q18
short answer
5 marks
What is the basic principle involved in RNA interference (RNAi) in silencing the preferred genes?
