How does circular DNA wrap around a histone to form a chromosome?

In summary, circular DNA does not wrap around a histone to form a chromosome. Instead, it is compacted in shape with the help of proteins such as HU. The histone proteins and DNA are attracted to each other through electrostatic forces, and transcription regulatory machinery helps regulate this process. This compacting of DNA allows for the formation of euchromatin and heterochromatin, which can be seen under electrophoresis and DNA banding patterns.
  • #1
gauss44
49
0
How does circular DNA wrap around a histone to form a chromosome? Or does it?

I am having a hard time visualizing this for any sort of circular DNA: prokaryotes, mitochondria, etc.

(This question was inspired by my reading about biology and reading that circular DNA does, in fact, form chromosomes. So, now I'm wondering how?)
 
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  • #2
come on, guys …

somebody must know the answer to this! :smile:​
 
  • #3
tiny-tim said:
come on, guys …

somebody must know the answer to this! :smile:​

I'm not a biologist, but this set of images from missouri.edu seems to explain it. I have no reason to think it's inaccurate.

http://web.missouri.edu/~vandorens/Biochem8240/lectures/Nucl_acid_supercoil_1oct12.pdf
 
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  • #5
gauss44 said:
How does circular DNA wrap around a histone to form a chromosome?

Histone are proteins made up of amino acids (basic) ex. lysine and arginine , that are positively charged.on the other hand DNA contains phosphorus backbone(PO4 3-). so this is an electrostatic attraction and nothing else.
also, some transcription regulatory machinery regulates this wrapping otherwise the length of DNA is 2.2m in Humans.
Due to this euchromatin and Heterochromatin is seen under Electrophoresis and DNA banding patterns.
 

1. How does circular DNA wrap around a histone to form a chromosome?

The process of circular DNA wrapping around a histone to form a chromosome is known as chromatin packaging. This process involves the binding of DNA to histone proteins, which are highly positively charged and can interact with the negatively charged phosphate backbone of DNA. The DNA is wrapped around the histone in a spiral shape, forming a nucleosome, which serves as the basic unit of chromatin.

2. What is the purpose of circular DNA wrapping around a histone to form a chromosome?

The main purpose of chromatin packaging is to compact and organize the DNA in the cell. This allows for the efficient storage of genetic material in the nucleus and also helps regulate gene expression by controlling access to specific regions of DNA.

3. How many histones are typically involved in the formation of a chromosome?

A chromosome is made up of multiple nucleosomes, each formed by one histone octamer (made up of 8 histone proteins) and about 147 base pairs of DNA wrapped around it. Therefore, a single chromosome can involve hundreds of histones.

4. Does circular DNA always wrap around histones to form a chromosome?

No, not all DNA in the cell is wrapped around histones. Some regions, called heterochromatin, are tightly packed and inaccessible for gene expression, while other regions, called euchromatin, are more loosely packed and accessible for gene expression. In both cases, the DNA is still organized and compacted, but it may not always involve histones.

5. Can circular DNA wrap around histones in different ways to form different types of chromosomes?

Yes, the specific arrangement and organization of DNA and histones can vary between different types of cells and organisms. For example, in humans, the DNA is wrapped around histones in a more complex structure known as a chromatin fiber, while in bacteria, the DNA is not bound to histones at all and is organized in a different way.

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