Science (English Medium) इयत्ता १२ - CBSE Important Questions for Biology

Name the greenhouse gases that contribute to global warming.

Answer the following question.
Two children, A and B aged 4 and 5 years respectively visited a hospital with a similar genetic disorder. The girl A was provided enzyme-replacement therapy and was advised to revisit periodically for further treatment. The girl, B was, however, given a therapy that did not require revisit for further treatment.

Name the ailments the two girls were suffering from?

Assertion: When the two genes in a dihybrid cross are situated on the same chromosome, the proportion of parental gene combinations is much higher than the nonparental type.

Reason: Higher parental gene combinations can be attributed to crossing over between two genes.

By using Punnett square depict the genotypes and phenotypes of test crosses (where green pod colour (G) is dominant over yellow pod colour (g)) in Garden pea with unknown genotype.

Describe the various steps of Griffith’s experiment that led to the conclusion of the 'Transforming Principle'.

How did the chemical nature of the ‘Transforming Principle' get established?

Answer the following question.
Construct and label a transcription unit from which the RNA segment given below has been transcribed. Write the complete name of the enzyme that transcribed this RNA. 

Write the contributions of the following scientists in deciphering the genetic code.
George Gamow; Hargobind Khorana; Marshall Nirenberg; Severo Ochoa

Answer the following question.
State the importance of a Genetic code in protein biosynthesis.

Explain the process of aminoacylation of tRNA and its role in the process of translation.

Given below is a stretch of DNA showing the coding strand of a structural gene of a transcription unit?

5’-ATG ACC GTA TTT TCT GTA GTG CCC GTA CTT CAG GCA TAA-3’

1. Write the corresponding template strand and the mRNA strand that will be transcribed, along with its polarity.
2. If GUA of the transcribed mRNA is an intron, depict the sequence involved in the formation of mRNA/the mature processed hnRNA strand.
   i. In a bacterium
   ii. In humans
3. Upon translation, how many amino acids will the resulting polypeptide have? Justify.

Mention the evolutionary significance of the Homo erectus

At which stage during evolution did human use hides to protect their bodies and buried their dead?

Why is secondary immune response more intense than the primary immune response in humans?

Answer the following question:
The principle of vaccination is based on the property of the "memory" of the immune system. Taking one suitable example, justify the statement.

Answer the following question.
Differentiate between the roles of B-lymphocytes and T-lymphocytes in generating immune responses.

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

Why is a malignant tumour considered to be more damaging than a benign tumour? Explain.

Name the type of association that the genus Glomus exhibits with higher plants.

Explain the process of sewage water treatment before it can be discharged into natural water bodies.