Subject

Biology

Class

CBSE Class 12

Pre Boards

Practice to excel and get familiar with the paper pattern and the type of questions. Check you answers with answer keys provided.

Sample Papers

Download the PDF Sample Papers Free for off line practice and view the Solutions online.
Advertisement

 Multiple Choice QuestionsShort Answer Type

21.

Describe any three potential applications of genetically modified plants.

1363 Views

22. How do snails, seeds, bears, zooplanktons, fungi and bacteria adapt to conditions unfavourable for their survival?
616 Views

23. How did an American Company. Eli Lilly use the knowledge of r-DNA technology to produce human insulin?
822 Views

24.

With the help of a flow chart, show the phenomenon of biomagnification of DDT in an aquatic food chain.

1394 Views

Advertisement
25.

Your school has been selected by the Department of Education to organize and host an interschool seminar on 'Reproductive Health – Problems and Practices'. However, many parents are reluctant to permit their wards to attend it. Their argument is that the topic is 'too embarrassing.'
Put forth four arguments with appropriate reasons and explanation to justify the topic to be essential and timely.

975 Views

 Multiple Choice QuestionsLong Answer Type

26.

(a) Plan an experiment and prepare a flow chart of the steps that you would follow to ensure that the seeds are formed only from the desired sets of pollen grains. Name the type of experiment that you carried out.

(b) Write the importance of such experiments.

1795 Views

27. Describe the roles of pituitary and ovarian hormones during the menstrual cycle in a human female.
1345 Views

28.

(a) Why are thalassemia and haemophilia categorized as Mendelian disorders ? Write the symptoms of these diseases. Explain their pattern of inheritance in humans.

(b) Write the genotypes of the normal parents producing a haemophilic son.

1803 Views

Advertisement
Advertisement

29. How do m-RNA, t-RNA and ribosomes help in the process of translation?


Translation is the process of polymerising amino acid to form a polypeptide chain.

The triplet sequence of base pairs in mRNA defines the order and sequence of amino acids in a polypeptide chain.

The process of translation involves the following three steps:



(i) Initiation

(ii) Elongation

(iii) Termination

  • During the initiation of the translation, tRNA gets charged when the amino acid binds to it using ATP.
  • The start (initiation) codon (AUG) present on mRNA is recognised only by the charged tRNA.
  • The ribosome acts as an actual site for the process of translation and contains two separate sites in a large subunit for the attachment of subsequent amino acids.
  • The small subunit of ribosome binds to mRNA at the start codon (AUG) followed by the large subunit. Then, it initiates the process of translation.
  • During the elongation process, the ribosome moves one codon downstream along with mRNA so as to leave the space for binding of another charged tRNA.
  • The amino acid brought by tRNA gets linked with the previous amino acid through a peptide bond and this process continues to result in the formation of a polypeptide chain.
  • When the ribosome reaches one or more stop codon (VAA, UAG and UGA), the process of translation gets terminated.
  • The polypeptide chain is released and the ribosomes get detached from mRNA.
934 Views

Advertisement
30.

(a) List the different attributes that a population has and not an individual organism.

(b) What is population density ? Explain any three different ways the population density can be measured, with the help of an example each.

606 Views

Advertisement