Chapter 12, Problem 8A

Summary Introduction

To analyze:

How DNA forms chromosomes in eukaryotic cells.

Introduction:

Eukaryotic cell: These are the cells that have a membrane-bound well-organized nucleus and have other membranous organelles.

DNA: Deoxyribonucleic acid is the double-stranded polynucleotide chain, made up of nitrogen base, deoxyribose sugar, and a phosphate group. It is the cell’s hereditary material.

Explanation of Solution

In a eukaryotic cell, DNA is organized into individual chromosomes. The negatively charged phosphate group of DNA attracts the positively charged Histone proteins. As a result, DNA tightly coils around this histone protein to form a bead-like structure called Nucleosome.

These Nucleosomes are grouped to form chromatin fibers, which are visible when a cell is in the resting phase or not dividing. When a cell starts to divide, these chromatin fibers are supercoiled and become visible as chromosomes.

Conclusion

The length of human chromosomes ranges from 51 million to 245 million base pairs and, the number of these chromosomes varies from species to species.