Genome organization Flashcards
Define synteny
Refers to two genes that are on the same chromosome
What percentage of the genome codes for protein
1.5%
What is the average length of an exon
100-200
What percentage of a gene is repetitive DNA?
50%
What is the average size of a gene?
27k
What are the four levels of DNA compaction?
- Nucleosome: beads on a string
- 30nm fibers
- Interphase chromosomes
- M-phase mitosis model
What is the diameter of a nucleosome?
10 nm
What are the four different proteins that make up the histone?
H2A, H2B, H3, H4
How many bp wrap around the histone?
146-147
In a complete nucleosome, how many bp?
200
What is an example of a function of the chromatin remodeling complex?
Spacing between histones
Name four covalent modifications to histone tails
- Lysine acetylation
- Lysine methylation
- Serine phosphorylation
- Ubiquitination
What enzyme carries out histone acetylation
histone acetyl-transferase
What protein is involved in modifying DNA trajectory upon leaving the nucleosome and forming 30nm fiber sturcture
Histone H1
The highly condensed form of chromatin
heterochromatin
The less condensed form of chromatin
euchromatin
Define constitutive heterochromatin
heterochromatin is tightly packed all the time
Define facultative heterochromatin
Applies to a region of the genome that is hetero- in some cell types, and not in others
Positional effect
The need for a gene to be in the right part of the genome in order to be expressed
What is able to block heterochromatin movement, and what is an example of this?`
Isolators: HS4 sequence
What is a “reader writer” complex?
A group of proteins that gather more more proteins which work together to compact DNA and create heterochromatin
What are tandemly repeated short sequences in the centromere called?
alpha satellite DNA
What is different about nucleosomes in the centromere?
They have a histone H3 variant named CENP-A
How many nucleotide pairs in an alpha satellite DNA monomer
171
What are two examples of interphase chromosome compaction
- lampbrush chromosomes (amphibian oocytes)
2. polytene chromosomes (drosophila salivary glands)
What is the highest level of chromatin compaction?
mitotic chromosomes
What are two roles of mitotic chromosome compaction?
- it untangles sister chromatids
2. protects DNA molecules while being pulled to daughter cells
What group of proteins are used to compact interphase chromosomes?
condensins
