Question Video: Understanding the Role of Proteins in DNA Compaction Biology

In the initial stages of chromosome formation, double-stranded DNA wraps around specialized proteins. What are these proteins called?

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Video Transcript

In the initial stages of chromosome formation, double-stranded DNA wraps around specialized proteins. What are these proteins called?

To answer this question, we need to understand how DNA is organized so that it can be packaged into chromosomes. Most cells in the human body contain 23 pairs of chromosomes, or 46 chromosomes in total. They’re found in the nucleus of cells. Chromosomes are made up of DNA that has been very tightly coiled. Genes are sections of chromosomes or indeed sections of DNA that contain the information needed to produce a particular characteristic, for example, a specific eye color.

If we were to unravel all the DNA that makes up all 46 chromosomes in a single cell nucleus, we would end up with around two meters of DNA in each nucleus. Obviously, this amount of DNA needs to be compacted in order to fit into the nucleus of a single cell. So let’s look in more detail about how this compaction of DNA takes place and what other sorts of molecules are involved. Histones are specialized structural proteins able to interact with DNA very closely. In this diagram, each histone is represented by a fuchsia circle. And you can see that there are eight histones grouped together with a strand of DNA wrapped around them.

Histones and DNA interact very closely together because of their opposite charges. Histones are positively charged, whereas DNA is negatively charged. This structure of eight histones with the DNA strand wrapped tightly around them is called a nucleosome. Nucleosomes are often compared to beads on a string, where the nucleosome is the bead and the DNA strand is the string. However, take note that, unlike normal beads on a string, the nucleosome has the string, or DNA strand, wrapped around it rather than going through the center. Chromatin fiber is formed when nucleosomes are packed tightly together. This chromatin is compacted even further to form a chromosome.

The question is asking us about the initial stages of chromosome formation. So let’s revisit the start of this process. If we go back to the start of our process, we will see that initially the DNA wraps around histones. So the answer to the question “In the initial stages of chromosome formation, double-stranded DNA wraps around specialized proteins. What are these proteins called?” the answer is histones.

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