Module 8 Lec 7 Flashcards
What is the complex of DNA and protein in eukaryotic chromosomes called?
Chromatin is the complex of DNA and protein in eukaryotic chromosomes.
What types of proteins are associated with eukaryotic chromosomes?
Histones and non-histone proteins are associated with eukaryotic chromosomes.
What is the ratio of DNA to histones to non-histone proteins in eukaryotic chromosomes?
The ratio is DNA : histone : non-histone = 1:1:1.
What are histones?
Histones are small proteins with basic, positively charged amino acids, like lysine and arginine.
What is the role of histones in relation to DNA?
Histones bind to and neutralize negatively charged DNA.
How many types of histones exist, and which ones make up the nucleosome?
There are five types: H1, H2A, H2B, H3, and H4. The core histones that make up the nucleosome are H2A, H2B, H3, and H4.
How is the synthesis of histones and DNA related?
Histone and DNA synthesis correlate in time, so both are synthesized together.
Why are histones highly conserved across species?
Histones are highly conserved because they are important for binding to DNA and show a high level of similarity among diverse organisms over millions of years of evolution.
What are non-histone proteins?
Non-histone proteins are a heterogeneous group of proteins with a large variety of functions.
What are some functions of non-histone proteins?
Non-histone proteins serve in functions like:
Scaffold (backbone of chromosome)
DNA replication (e.g., DNA polymerases)
Chromosome segregation (e.g., motor proteins of kinetochores)
Transcriptional regulation (largest group)
How do non-histone proteins vary in different tissues?
Non-histone proteins occur in different amounts in different tissues, reflecting their variety of functions.
What is the structure of nucleosomes?
Nucleosomes are composed of DNA wrapped around histone proteins, forming structures that resemble beads on a string.
What histones are involved in the nucleosome core?
The nucleosome core is made of H2A, H2B, H3, and H4 histones.
What is linker DNA?
Linker DNA is the stretch of DNA between nucleosomes, connecting them, and is not wrapped around histones.
What role does H1 histone play in nucleosomes?
The H1 histone binds to the linker DNA and helps stabilize the nucleosome structure, aiding in higher-order chromatin packaging.
How is DNA organized in nucleosomes?
DNA is wrapped around an octamer of H2A, H2B, H3, and H4 histones, creating the nucleosome core.
What is a nucleosome?
A nucleosome is the basic unit of chromatin, consisting of eight histone proteins (an octamer) wrapped by around 160 bp of DNA.
What histones make up the nucleosome octamer?
The nucleosome octamer consists of:
2x H2A
2x H2B
2x H3
2x H4
How is the DNA wrapped around the nucleosome?
About 160 base pairs (bp) of DNA are wrapped twice around the histone octamer.
What is the role of H1 histone in nucleosomes?
H1 binds to the linker DNA, stabilizing the nucleosome where the DNA enters and exits.
What is linker DNA?
Linker DNA is the stretch of DNA, approximately 40 bp long, that connects adjacent nucleosomes.
How does DNA sequence influence histone binding?
The DNA sequence can affect where and how histones bind, influencing the spacing between nucleosomes, which in turn impacts gene expression.
How does nucleosome spacing affect gene expression?
The spacing of nucleosomes affects gene accessibility, influencing whether genes are turned on or off.
How is nucleosome spacing inherited?
The spacing of nucleosomes is faithfully inherited by daughter chromosomes during cell division.
How much does packaging into nucleosomes condense DNA?
Packaging into nucleosomes condenses DNA sevenfold, shortening 2 meters of DNA to less than 0.25 meters (250 mm).
What is the average diameter of a eukaryotic cell?
The average diameter of a eukaryotic cell is approximately 10-30 micrometers (μm).
What is the 300 Å fiber in chromosome compaction?
The 300 Å fiber is formed by the supercoiling of nucleosomes into a higher-order structure, helping further condense the chromatin.
What is the Radial Loop-Scaffold Model in chromatin compaction?
The Radial Loop-Scaffold Model describes how loops of DNA (60-100 kb) are anchored to a scaffold of non-histone proteins, creating higher levels of chromatin compaction
How much more compact is DNA in metaphase compared to its linear state?
In metaphase, DNA is 10,000 times more compact than in its linear state.