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MODEL PAPER 2025 — BIOLOGY STD 12 Science — Question

Bihar BoardEnglish MediumSTD 12 ScienceBIOLOGYMODEL PAPER 20253 Marks
Question
The schematic representation given below shows the concept of Central Dogma.
Image
A. During the process of replication and transcription the pairing of
nitrogenous bases is not similar. Explain.
B. How is the above process modified in a retrovirus? Name the process.
C. Justify why during the process of transcription only a segment of DNA is copied into RNA.
✓

Answer

A. During replication, Adenine pairs with thymine in DNA; during transcription, adenine pairs with uracil in RNA.
B. In retrovirus the nucleic acid is RNA and it is used to synthesize DNA; the process is called reverse transcription.
C. It is a highly energy-rich process/ or as per the need only the gene coding for a specific protein is transcribed.

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