DNA of the Human Body Calculate the weight in grams of a...

DNA of the Human Body Calculate the weight in grams of a double-helical DNA molecule stretching from Earth to the moon $(\sim 320,000 \mathrm{km}) .$ The DNA double helix weighs about $1 \times 10^{-18}$ g per 1,000 nucleotide pairs; each base pair extends 3.4 A. For an interesting comparison, your body contains about 0.5 g of DNA.

Key Concepts

DNA Double Helix Structure

This concept refers to the well-known double-stranded, spiral structure of DNA that holds genetic information. Understanding that the DNA molecule is arranged in a helical structure, with two strands connected by base pairs, is essential when exploring its physical properties, such as length and mass distribution, over macroscopic distances.

Nucleotide Pair Weight and Length

Fundamental to the calculation is the property of a nucleotide pair, which has both a measurable mass and a defined spatial extension along the DNA helix. Recognizing the typical weight per set of nucleotide pairs and the average spacing between them provides the molecular basis for converting between count and physical length.

Unit Conversion and Dimensional Analysis

This key concept involves converting units to ensure consistency throughout the calculation. When dealing with measurements at the molecular scale (such as angstroms) and astronomical scales (such as kilometers), unit conversion is critical. This process often includes converting angstroms to centimeters or kilometers to angstroms, allowing for accurate computation of physical quantities like length and weight.

Scaling and Estimation Techniques

Scaling involves extrapolating known molecular properties to macroscopic dimensions, such as calculating the total DNA mass over a large distance. Estimation techniques use given orders of magnitude and approximation methods to determine the overall impact when a small-scale measurement (e.g., weight per 1000 nucleotide pairs) is applied to very large-scale phenomena, such as spanning the distance from Earth to the Moon.

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