Answer: DNA double helix, nucleosome, chromatin fibre (beads on string and higher coiling), chromosome.
- A Chromosome, then nucleosome, then chromatin fibre, then finally the DNA double helix itself
- B DNA double helix, nucleosome, chromatin fibre (beads on string and higher coiling), chromosome
- C Nucleosome, then chromosome, then the DNA double helix, then finally the chromatin fibre itself
- D Chromatin fibre, then chromosome, then nucleosome, then finally the DNA double helix itself
Correct answer: B. DNA double helix, nucleosome, chromatin fibre (beads on string and higher coiling), chromosome
Explanation: Packaging proceeds from the naked DNA double helix wrapping around histones to form nucleosomes (beads on a string), which further coil into chromatin fibres, which condense further to form a visible chromosome.
Helicase unwinds the double helix at the replication fork; one new strand (leading) is synthesised continuously toward the fork, while the other (lagging) must be made in short, separate Okazaki fragments because DNA polymerase only adds nucleotides 5'→3'.
Concept context
DNA structure, replication, transcription, translation, the genetic code, and gene regulation (lac operon). The single most important chapter for NEET molecular biology.