Chromatin Flashcards by Eric Cao

How many chromosome in human DNA

46 Chromosomes

23 Pairs

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Mitosis Phases

Interphase
Prophase
Metaphase
Anaphase 
Telophase/Cytokinesis

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Interphase

When DNA replicates includes G1/S/G2 and G0 phase(for non dividing cells)

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Histone Function

Created during G1 phase.
It packages DNA into structured units
Protect DNA and regulate replication and transcription

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G2 Phase

DNA content doubled ready for Mitosis using the chromatin that uses histone and non histone chromatin

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G1 Phase

Histone synthesis

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S Phase

DNA replication begins as G1 phase still continue s making Histone

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Non Dividing Eukaryotic Cells have _____ Chromatin Fiber

Solenoid

Straight noodle looking.

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Chromatin in Dividing Eukaryotic Cells are _______

Condensed chromosomes that are heterochromatin that have telomere centromere and arms.

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Nuclear Lamina

Made of nuclear lamin proteins that form intermediate filaments that provide structure for nucleus

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What organelle does the Endoplasmic Reticulum share a nuclear membrane with?

Nucleus

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Nucleolus

Produces ribosome in a sub compartment in nucleus

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10% of Chromosome arm in Metaphase form has around how many genes

40 Genes

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Chromatin Consist Of?

Equal DNA and Protein with a little bit of RNA

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First Tier Chromatin package

Nucleosomes

Bead on string

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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