Question

These sequence of events mentioned below are symbolised by alphabets. Choose the correct answer where the alphabets are matched with the processes.
$RNA\stackrel{a}{\to }DNA\stackrel{b}{\to }DNA\stackrel{c}{\to }mRNA\stackrel{d}{\to }Polypeptide$

• A. a - Reverse transcription, b - Replication, c - Transcription, d - Translation
• B. a - Replication, b - Transformation, c - Transcription, d - Translation
• C. a - Reverse transcription, b - Transformation, c - Transcription, d - Translation
• D. a - Replication, b - Transduction. c - Translation, d - Transcription

Answer 1

Answer: (A)

a - Reverse transcription, b - Replication, c - Transcription, d - Translation

The DNA synthesized using RNA template is known as cDNA or complementary DNA. RNA retroviruses have reverse transcriptase enzyme that synthesizes a DNA copy (cDNA) of viral RNA by reverse transcription (a) The cDNA is made into double stranded molecule by DNA replication (b) which is integrated into host genome. The host DNA is replicated using host cell machinery, DNA polymerase using the parental DNA template, not by reverse transcriptase. Option B is incorrect. The DNA is first transcribed (c) by host cell RNA polymerase and then translated (d) into polypeptide using host cell machinery. Option A is correct.

Transformation is the transfer of genetic material from one bacterial strain to other without establishing a physical contact. Transduction is the transfer of genetic material from one strain to other via viral particles. The virus infects bacteria and released viral particles carry part of a bacterial genetic material which is then transferred to next host bacterium. Both transformation and transduction are the mode of sexual reproduction in bacteria and are not involved in gene expression pathway which makes options B, C and D incorrect.