question_answer

Enlist the main differences between the two types of nucleic acids found in living systems.

Or

Study the figure given below and answer the following questions

(i) Identify the molecule 'X' synthesised by 'i' gene. How does this molecule get inactivated?

(ii) Identify the structural gene that codes for \[\beta \]-galactosidase.

(iii) When does the transcription of this gene get stopped?

Answer:

Differences between nucleic acids, i.e. DNA and RNA are as follows

DNA	RNA
It is the genetic material found in most of the organisms.	It is the genetic material in only some viruses.
It is mainly double-stranded with exception to some viruses (e.g. single-stranded in\[(\Phi \times 174)\].	It is single-stranded with exception to some viruses (e.g. double-stranded in retrovirus).
The sugar found is deoxyribose.	The sugar found is ribose.
Nitrogenous bases present are adenine, guanine, thymine and cytosine.	Nitrogenous bases present are adenine, guanine, cytosine and uracil.
It is chemically less reactive and structurally more stable.	It is chemically more reactive and structurally less stable.
It has the ability to replicate itself.	It is formed by DNA transcription.
(i) Molecule 'X' synthesised by 'i' gene is a represser protein. It gets inactivated on comhiniltd with an inducer molecule.
(ii) 'Z' gene codes for \[\beta \]-galactosidase.
(iii) Transcription of gene stops in the following conditions
(a) When substrate lactose is not available.
(b) When energy source, i.e. glucose is available to the cells.