Chromatin Flashcards
How many chromosome in human DNA
46 Chromosomes
23 Pairs
Mitosis Phases
Interphase Prophase Metaphase Anaphase Telophase/Cytokinesis
Interphase
When DNA replicates includes G1/S/G2 and G0 phase(for non dividing cells)
Histone Function
Created during G1 phase.
It packages DNA into structured units
Protect DNA and regulate replication and transcription
G2 Phase
DNA content doubled ready for Mitosis using the chromatin that uses histone and non histone chromatin
G1 Phase
Histone synthesis
S Phase
DNA replication begins as G1 phase still continue s making Histone
Non Dividing Eukaryotic Cells have _____ Chromatin Fiber
Solenoid
Straight noodle looking.
Chromatin in Dividing Eukaryotic Cells are _______
Condensed chromosomes that are heterochromatin that have telomere centromere and arms.
Nuclear Lamina
Made of nuclear lamin proteins that form intermediate filaments that provide structure for nucleus
What organelle does the Endoplasmic Reticulum share a nuclear membrane with?
Nucleus
Nucleolus
Produces ribosome in a sub compartment in nucleus
10% of Chromosome arm in Metaphase form has around how many genes
40 Genes
Chromatin Consist Of?
Equal DNA and Protein with a little bit of RNA
First Tier Chromatin package
Nucleosomes
Bead on string
Why Histones are major components of chromatin
25% Lysine/Arginines to equalize the high charged DNA
5 Type of Histone and Function
H2A H2B H3 H4
Core histones that use 2 of each to create octomer that DNA can wrap around
H1
Clamps DNA that is wrapped around the Core
When nucleosomes compress into stage 2 of a 30nm Fibre where is the H1 located on the solenoid.
Interior
Solenoid
The nucleosome compressed packed into a 30nm structure
What proteins cause the DNA duplex to open up during transcription?
Histone modifying enzymes
Chromatin Remodeling Protiein
Does the whole chromosome compact into 30nm Fibres?
No, some spots that are being actively transcribed have little or no H1 more disordered
Nuclear Scaffold
Made of H1 and Topoisomerase II present to supercoil DNA in chromatin assembly
What happens when you coil a coiled chromatin
DNA becomes TRANSCRIPTIONALLY SILENT
How is a head to tail dimer made?
Handshake interaction between H2A H2B histones. Where N terminal of 1 connects with C terminal of another.
Histone Core
2 H3 H4 Dimers
+ 2 H2A H2B Dimers
=Octomer core
N terminal tails
stick out of histone octamer but no specific orientation and are flexible/invisible.
Positive
DNA wraps around the histone octomer with ____ turns of NEGATIVE super coil
1.65
Chromatin Remodeling
Remodeling chromatin by modifying histones using enzymes to make the DNA more accessible (The parts that are used for expression and parts that need fixing)
Can Chromatin Remodeling cause nucelosomes to move to a different location?
Yes
It can move locations and make DNA more accessible
Its done by hydrolzing ATP
Chromosome Transmission is controlled by?
Replication origin more than 1
Centromere 1
Telomere 2
Centromere is?
Attachment site for mitotic spindle because of KINETOCHORE
Allows for 1 copy of chromosome to be pulled to each daughter cell
Replication Origin
Spot of DNA Replication start
More than one so fast replication
Telomere
End of chromosomes
Protects Ends from being eaten by nucleases
HIGHLY REPETITIVE SEQUENCE
How to complete the 5’ end of DNA due to missing 3’OH to fill in strand.
In other parts of the DNA its provided by the Okazaki fragment
Telomerase adds sequence to existing telomeres
Telomerase What Do?
Enzyme contains RNA component around 150 nucleotides long that acts as a template for telomere, by extending the 3’ end.
How to protect the ssDNA ends
Lower Eukaryotes specific binding proteins protect
Higher Eukaryotes have a T-Loop created by TRF1 and TRF2
