33. In an organism, the amount of DNA per haploid genome is about 1.6 x 109 nucleotide pairs. Given that the
length of DNA helix occupied by one nucleotide pair is 3.4 Å, approximately how long a double helix could
be formed from this DNA?
1. 22 cm
2. 55 cm
3. 1.1meter
4. 2.2 meter

Calculating the Length of a Double Helix from Nucleotide Pairs

In molecular biology, the structure of DNA is crucial to understanding genetics, replication, and protein synthesis. One interesting question is how long a DNA double helix would be, given the amount of nucleotide pairs in a haploid genome. Let’s break down how to calculate this length.

Given Data:

• Amount of DNA per haploid genome: 1.6 × 10⁹ nucleotide pairs

• Length occupied by one nucleotide pair: 3.4 Å (angstroms), which is equivalent to 3.4 × 10⁻¹⁰ meters.

Step-by-Step Calculation:

1. Determine the Total Length: The total length of the DNA double helix is calculated by multiplying the number of nucleotide pairs by the length occupied by each pair.

   $$\text{Total Length}=\text{Number of Nucleotide Pairs}\times \text{Length per Nucleotide Pair}$$

   Substituting the values:

   Total Length=1.6×109×3.4×10−10 meters\text{Total Length} = 1.6 \times 10^9 \times 3.4 \times 10^{-10} \, \text{meters}Total Length=1.6×109×3.4×10−10meters

   This results in a length of 0.544 meters or 54.4 cm.

2. Conversion to Centimeters: Since 1 meter equals 100 centimeters, we convert the result to centimeters:

   $$\text{Total Length in cm}=0.544\text{m}\times 100=54.4\text{cm}$$

Thus, the length of a double helix formed from this DNA is approximately 55 cm.

Correct Answer:

• 2. 55 cm

Why Does This Matter?

This calculation helps visualize the extraordinary structure of DNA and its packaging within cells. Despite its large length, DNA fits into the tiny nucleus of a cell through the process of DNA packaging and chromosome formation, allowing the genetic material to function efficiently.

Summary

When you consider the DNA in a haploid genome (1.6 × 10⁹ nucleotide pairs), the total length of a double helix formed would be around 55 cm. This can be derived by multiplying the number of nucleotide pairs by the length each pair occupies and converting the result into centimeters. The final answer is 55 cm, confirming the remarkable ability of cells to store vast amounts of genetic information within a confined space