Molecular Biology

Case (a) — Frame 1:
The sequence is: CUC GCU UUG CCG AUC AAG GGU UA
Grouping codons from the first nucleotide: The last codon fragment “UA” is incomplete (only 2 bases), so it will not be translated.
Total amino acids in case (a): 7 Case (b) — Frame 2:
The sequence is: GUG GCA CUC AGU CCU UAA UGG CG
Grouping codons from the second nucleotide: Translation terminates at the stop codon UAA. So, codons after UAA will not be translated.
Total amino acids in case (b): 5

(a) Step 1: The correct diagram is (ii).
Step 2: DNA replication occurs in the 5′ to 3′ direction. At the replication fork, one strand (leading strand) is synthesized continuously, while the other (lagging strand) is synthesized discontinuously in short fragments.
Step 3: In diagram (ii), both forks show correct orientation: the leading strand is synthesized towards the fork and the lagging strand away from it, consistent with the antiparallel nature of DNA and enzymatic action of DNA polymerase.
(b) Step 1: The enzyme used is DNA ligase.
Step 2: DNA ligase joins Okazaki fragments on the lagging strand by catalyzing the formation of phosphodiester bonds.

The Central Dogma of Molecular Biology

Step 1: Understanding the Central Dogma

The central dogma of molecular biology is a foundational concept that describes the flow of genetic information in biological systems. It suggests that:

• DNA is transcribed into RNA
• RNA is translated into Protein

This concept was first proposed by Francis Crick in 1957 and is unidirectional, meaning the flow of information goes in one direction: from DNA to RNA to protein.

Step 2: The Direction of Genetic Information Flow

The central dogma proposes that the genetic information flows in the following direction:

DNA → RNA → Protein

This unidirectional flow of genetic information was a groundbreaking idea and helped to establish the fundamental framework of molecular biology.

Step 3: Conclusion

Thus, the person who proposed the unidirectional flow of genetic information is Francis Crick. Therefore, the correct answer is Option (B).

Step 1 (a): The structure shown in the figure is a **nucleosome**, the fundamental unit of chromatin packaging in eukaryotes.

Step 2 (b):
Label P – DNA strand
Label Q – Histone core (octamer of histone proteins)

Step 3 (c): Histone proteins are **basic** in nature due to the abundance of positively charged amino acids (like lysine and arginine) which bind to the negatively charged DNA.

Step 4 (d):