Important Questions for Class 12 Chapter 6 - Molecular Basis of Inheritance

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Important questions based on NCERT syllabus for Chapter 6 - Molecular Basis of Inheritance:

Question-1: If a double stranded DNA has 20 per cent of cytosine, calculate the per cent of adenine in the DNA.

Solution: In a DNA molecule, the number of cytosine molecule is equal to guanine molecules & the number of adenine molecules are equal to thymine molecules. As a result, if a double stranded DNA has 20% of cytosine, it has 20% of guanine. The remaining 60% includes both adenine & thymine which are in equal amounts. So, the percentage of adenine is 30%.

Question-2: List two essential roles of ribosome during translation.

Solution: Two essential roles of ribiosomes during translation are ;o
(i)they provide surface for binding of mRNA in the groove of smaller sub unit of ribosome.
(ii)As larger sub unit of ribosome has peptidy transferase on its ā€˜Pā€™ site, therefore, it helps in joining amino acids by forming peptide bonds. .

Question-3: In the medium where E. coli was growing, lactose was added, which induced the lac operon. Then, why does lac operon shut down some time after addition of lactose in the medium?

Solution: Lac operon is switched on adding lactose in the medium, as lactose acts as inducer and make repressor inactive. Due to this switch on of lac operon system, (3-galactosidase is formed which converts lactose into glucose and galactose. As soon as lactose is consumed, repressor again become active and cause switch off (shut down) of system.