The fold compaction of DNA within chromatin is calculated as the ratio of the extended DNA length to the chromatin length, yielding an integer value of 170.

Calculation Steps

DNA length per base pair in B-form is 0.34 nm, or 3.4×10-8 cm. For 5×109 base pairs, extended length L = 5×109 × 3.4×10-8 = 170 cm. With chromatin length of 1 cm, fold compaction = 170/1 = 170. This matches typical chromatin packaging levels for such DNA quantities.

Problem Solution

DNA in B-form double helix measures 0.34 nm (or 3.4×10-8 cm) per base pair. For 5×109 base pairs, total extended length calculates as:

L = 5×109 × 3.4×10-8 = 1.7×102 cm = 170 cm.

Within 1 cm chromatin, fold compaction equals the length ratio: 170 cm/1 cm = 170.

Step-by-Step Calculation

  • Convert base pair spacing: 0.34 nm = 0.34×10-7 cm.
  • Multiply by base pairs: 5×109 × 0.34×10-7 = 170 cm.
  • Divide by chromatin length: 170/1 = 170 (integer).

No options provided; this numerical fill-in yields 170 directly.

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Introduction to DNA Fold Compaction in Chromatin

DNA fold compaction in chromatin packs vast genomic DNA into tiny nucleus space, crucial for cell function. For 5 × 109 base pairs in 1 cm chromatin, this metric shows packaging efficiency—key for CSIR NET aspirants studying molecular biology. Understanding fold compaction reveals nucleosome and higher-order folding mechanisms.

Step-by-Step Calculation

  • Base Pair Length: Each contributes 0.34 nm (3.4×10-8 cm).
  • Extended DNA Length: 5×109 × 3.4×10-8 = 170 cm.
  • Fold Compaction: Ratio = extended length / chromatin length = 170/1 = 170 (integer).

No options provided; direct integer answer is 170, aligning with human diploid-like DNA (~6 × 109 bp, ~2 m extended).

Biological Significance

DNA fold compaction in chromatin starts with nucleosomes (7-fold), reaches ~10,000-fold in metaphase chromosomes via loops and scaffolds. Histone H1 enhances compaction under force. For 5 × 109 base pairs, 170-fold suits interphase chromatin fibers.

Core Formula Breakdown

Fold compaction divides extended DNA length by packaged length. Each base pair spans 0.34 nm in B-DNA helix rise. For 5×109 base pairs:

Length = 5×109 × 0.34×10-7 cm = 170 cm.

Packaged at 1 cm, compaction ratio: 170-fold.

Biological Context

Nucleosomes wrap ~147 bp around histones (7-fold compaction), followed by 30-40 nm fiber (6-fold), loops, and scaffolds for ~10,000-fold total in metaphase chromosomes. This query isolates linear fold compaction, matching 170.

CSIR NET Exam Tips

  • Memorize: 0.34 nm/bp, human diploid ~6 × 109 bp (~2 m extended).
  • Verify units: nm to cm for cm-scale chromatin.
  • Common trap: Forgetting 10-7 cm/nm conversion.
  • Keywords: DNA fold compaction, chromatin compaction, 5 × 109 base pairs, 1 cm chromatin, 0.34 nm base pair