Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
27 Cards in this Set
- Front
- Back
|
Histones are made of 4 unique proteins which eventually form a dimer or dimers. How do the 4 proteins oligomerize into the octomer |
H2A and H2B dimerize H3 and H4 dimerize Then both H3/H4 dimer forms a tetramer which recruits H2A/HB2 dimers 1 at a time NO H2A/H2B tetramers form |
|
|
Describe the structure of a histone |
Each histone has 8 proteins 2 copies of each H2A/H2B complex 2 copies of each H3/H4 complex
Total: 4 sets of dimers leading to a octamer |
|
|
Define nucleosome |
8 protein histone core + DNA |
|
|
What is the 10nm fiber? |
"Beads on a string" represents the diameter of nucleosome |
|
|
What is the purpose of the H1 histone. Where is it found? |
It is a linker histone that aids in supercoiling that is found between nucleosomes |
|
|
What's the charge on a histone and why? |
Positively charged due to ~30% composition being lysine and arginine |
|
|
How many turns of DNA per histone octomer? |
1.7 turns |
|
|
What feature of the H3 and H4 suggests that a mutation in their units could be lethal |
H3 and H4 sequences are highly conserved |
|
|
What's the dimaeter of the successive stages of consendation? |
10-nm beads on a string 30-nm chromatin fiber 300-nm coiled chromatin fiber 700-nm coiled coil chromatin fiber 1400-nm metaphase chromatid |
|
|
What is the average length of a DNA fragments per Nucleosome after light nuclease digestion? |
200 bp |
|
|
What is the average length of core DNA per core particle after heavier nuclease digestion and why? |
145 bp because the linker protein is cleaved |
|
|
Presense of Cyclin ___ signifies the start of the cell cycles within the cell |
Cyclin D |
|
|
What are the histone structural motifs? |
Solenoid model, helical ribbon model, and crossed-linker model |
|
|
Why are there different levels on compaction? |
To regulate gene expression |
|
|
What factors impact the organizational structure of a chromosome? |
Stress and environmental factors |
|
|
What level of chromosomal organization does NOT involve the H1 histone? |
10-nm "beads on a string" organization |
|
|
What organizational motif is seen in the first step of supercoiling and describe this structure. |
Solenoid structure with is 6-8 nucleosomes brought together |
|
|
What is the significance of H1 on gene expression? |
If we want to express genes in a 30nm structure, we would need weak H1 interactions to access it
So binding affinity is related to expression |
|
|
What is the function of topoisomerase in super coiling? |
It relieves stress and increases coiling to supercoiling |
|
|
What is the role of methylation? |
Shield promoter region |
|
|
Order histones by their tail length |
H3 > H4 > H2A |
|
|
What are the 3 ways a histone tail can be modified? What are their effects on the electrostatic environment? |
Acetylation - Shields positively charged histones Methylation - no effect on charge Phosphorylation - adds another negative charge |
|
|
What types of chromatin are there and how can we distinguish them? |
1) Euchromatin is visible only after mitosis promoted condensation 2) Heterochromatin is visible during interphase as a compact structure. Usually adjacent to centromere |
|
|
Heterochromatin can be divided into 2 subgroups, what are they? |
Faculative heterochromatin Constitutive heterochromatin |
|
|
How do the repetitive sequences of heterochromatin differ between subgroups? |
Faculative contains SINES and LINES repeats
Constitutive contain satellite repeasts |
|
|
In what chromosomal regions is cross over most frequent? |
euchromatin regions |
|
|
Compare the genetic diversity of heterochromatin to euchromatin |
# of genes in heterochromatin is less than in euchromatin |
