Chromosomes and Chromatin Flashcards
Are chromosomes condensed or decondensed during interphase?
decondensed
What is the only structure not in the interphase nucleus?
metaphase chromosomes
What is the only type of chromosome visible with a light microscope?
metaphase chromosome
What happens in between cytokinesis and interphase?
nucleus reforms and chromosomes start to decondense
What is a karyotype?
homologous chromosomes paired up from largest to smallest
How many sister chromatids are in each homolog?
2
Histones have what amino acids?
arginine and lysine
What are non histone chromosomal proteins?
- DNA & RNA polymerase
- proteins that regulate transcription
What are the histone molecuels in nucleosomes?
- H2A
- H2B
- H3
- H4
What are nucleosomes made of?
150 base pairs of DNA wrapped twice around 8 histones
What are the 2 terminus on a histone?
- C = inside histone core
- N = histone tails on outside (+ to interact with DNA)
What is the difference between condensed and decondensed chromatin?
- condensed = heterochromatin = NO transcription
- decondensed = euchromatin = needed for RNA transcription
What can histone modification do?
- directly affect chromatin structure due to electrostatic interactions
- create binding sites for proteins that use gene expression or chromatin condensation
Where does post translational modification of histones occur?
N terminal
What are the modifications that open chromatin?
- acetylation: adds acetyl group
- demthylation: removes methyl group
What are the modifications that close chromatin?
- deactylation: removes acetyl group
- methylation: adds methyl group
What chromatin remodeling protein leads to methylation at lysine 9 and condenses chromatin?
HP1
What do histone acetyl transferases (HATs) do?
- add acetyl group to lysines
- OPEN chromatin -> transcription
What do histone deactylases (HDACs) do?
- removes acetyl group from lysines
- CLOSED chromatin -> no transcription
What do histone methylations (HMATs) do?
- adds methyl group to lysines and arginines
- CLOSED chromatin -> no transcription
What do histone demthylations (HDMTs) do?
- removes methyl group
- OPEN chromatin -> transcription occurs
What is the chromatin remodeling complex?
- requires ATP
- stabilizes nucleosomes
What are the steps in the pre-initiation complex?
- nucleosome trancribed as H3K4 methylation
- TF2D recoognizes H3K4 and brings in RNA polymerase
- H3K4 binds to TF2D
- TF2D phosphorylates poly carbon terminal to initiate transcription
What recruits HATs?
transactivators
