Lecture 15 - Chromatin Flashcards
What does packaging do?
Compacts the DNA, protects it from damage and contributes to regulation of replication & transcription
When is DNA present as chromatin?
During interphase
During what phase does DNA replication occur?
S phase
What are histones?
Proteins that package and order the DNA into structured units
What is chromatin comprised of?
DNA, histones, and non-histone proteins
Where are proteins modified and where does maturation of proteins happen?
Endoplasmic reticulum
What is the nuclear lamina?
The inner surface of the nuclear envelope - it is line w/ proteins called nuclear lamins that form intermediate filaments that also extend across the cytoplasm to provide structural support
What are components of the nucleus?
Endoplasmic reticulum, nuclear pore complex, nuclear lamina, nuclear matrix, nucleolus, nucleoplasm, chromatin
What is the function of the nuclear matrix?
To diffuse nuclear scaffold consisting of proteins that attach chromosomes to the nuclear envelope or other structures in the nucleus
What is the nucleoplasm?
Chromatin/chromosome-containing region
What is the nucleolus?
A ribosome-producing sub-compartment of the nucleus
What are the 3 levels of DNA packaging? At which level allows DNA replication & RNA transcription?
3 levels:
- 11 nm nucleosomes
- 30 nm chromatin fibers (solenoids) > also phase where DNA replication and RNA transcription happens
- 700 nm condensed chromosomes (metaphase chromosomes 1400 nm)
What are the 2 processes that change the accessibility of DNA to DNA binding proteins to allow or regulated replication
Histone modification and chromatin remodeling
What effect does acetylation of histone lysines have on chromatin structure?
- loss of positive charge reduces binding to DNA and destabilizes chromatin
- acetylated regions attract proteins that can either cause further compaction or can facilitate access to DNA
Bacteria do not have telomerases. Why is that?
- Bacteria do not have telomerases because their DNA is circular. Telomerases help compensate for incomplete semi-conservative DNA replication at chromosomal ends (eukaryotic cells)
