DNA Packing Flashcards
What is the primary protein that complex DNA in eukaryotes?
Histones
Histones are proteins that help package DNA into a more compact structure.
What is the term used to describe the highly dense structures formed by DNA and histones?
Quaternary Structure
This term refers to the complex assembly of proteins and nucleic acids.
What is the length of chromosomal DNA in eukaryotes?
Just under 0.05m
This length is significantly reduced when compacted into chromosomes.
What is the typical length range of chromosomes in eukaryotes?
1 to 10µm
Chromosomes are much shorter than the total length of chromosomal DNA.
List the levels of packaging for eukaryotic DNA.
- Nucleosomes
- Loops of fibers (beads-on-a-string)
- 30mm fibers
These levels represent the hierarchical organization of DNA.
Fill in the blank: Eukaryotic DNA is complexed to _______ to form a highly dense structure.
Histones
This complex formation is essential for DNA packaging.
What is the basic unit of Eukaryotic chromosome structure?
Nucleosome
What proteins make up the histone core of a nucleosome?
Four pairs of protein monomers: H2A, H2B, H3, and H4.
What is the composition of the nucleosome core particle?
A histone octamer and about 146 base pairs of DNA.
What is the diameter of a nucleosome?
5.7 nm
What additional component does each nucleosome contain?
Histone H1 and linker DNA.
How long is the linker DNA in a nucleosome?
About 54 base pairs.
What role does Histone H1 play in the nucleosome?
It binds to the core particle and to linker DNA.
What is the diameter of the nucleosome structure?
11 nm
What does ‘beads-on-a-string’ packaging of DNA represent?
It represents the 1st level of chromosomal packing.
What is the ‘beads-on-a-string’ form of chromatin composed of?
Beads = core nucleosome (11 nm)
String = DNA
How are nucleosomes connected together?
Nucleosomes are connected together by linker DNA and histone (H1).
What is the diameter of the resulting chromatin fiber?
The resulting fiber is about 30nm in diameter.
How do nucleosomes associate with each other?
Nucleosomes can associate with each other through interactions between histone H1 to form a more compact structure (chromatin fiber).
What is the effect of 30nm fiber packaging on DNA?
It makes DNA even more condensed.
How is the chromatin fiber structured?
Packed on top of one another, generating a regular array.
What is the diameter of the resulting chromatin fiber?
The resulting fiber is about 30nm in diameter.
How do nucleosomes associate with each other?
Nucleosomes can associate with each other through interactions between histone H1 to form a more compact structure (chromatin fiber).
What is the effect of 30nm fiber packaging on DNA?
It makes DNA even more condensed.
How is the chromatin fiber structured?
Packed on top of one another, generating a regular array.
What type of DNA do prokaryotes have?
Prokaryotic DNA is circular and double-stranded.
What happens to the double helix during prokaryotic DNA packaging?
A few turns of the double helix are removed.
What is formed when prokaryotic DNA is supercoiled?
The molecule forms a negative supercoil.
How do prokaryotes compress their DNA?
Prokaryotes compress their DNA into smaller spaces by supercoiling.
What is the role of multiple proteins in prokaryotic DNA packaging?
Multiple proteins act together to fold and condense prokaryotic DNA.
What are HU proteins?
HU proteins are a type of protein involved in prokaryotic DNA packaging.
How do HU proteins interact with DNA in E. coli?
HU proteins in E. coli form a tetramer wound with about 60bp of DNA.
How many HU proteins are present in an E. coli cell?
There are about 60,000 HU proteins per E. coli cell.
What is the structure of E. coli nucleoid?
E. coli nucleoid model shows DNA packed in a protein core by HU proteins.
