Chromatin Structure Part 2 Flashcards Preview

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Flashcards in Chromatin Structure Part 2 Deck (13):

In a "normal" nucleosome

- DNA coils around the histone octomer in a left handed coil
- and negatively supercoiled (right handed supercoils)


nucleosome core

- histone octomer
- 146 bp DNA
- 1 3/4 turns

- results from a limit digest of chromatin by micrococcal nuclease


complete nucleosome

- contains 146 bp DNA + octomer (nucleosome core)
- spacer of ~54 bp DNA

- room enough for H1 histone to bind
- definition does not include H1


linker DNA

- variable
- holds cores together


linker histones

facilitates folding of 10 nm fiber (beads on a string) into 30 nm fiber


chromatin containing H1

- nucleosomes with regular zigzag orientation


no H1

- beads on a string


nucleosome ladders

- microccal nuclease-generated nucleosome ladder of chromatin
- if chromatin was uniform you would get a smear of DNA
- provided evidence for particulate structure of chromatin.


transgenic marker genes

- used to determine if piece of DNA has been successfully inserted into the genome of the host organism
- gene from one organism put into another


selective markers

- genes that protect the transformed organism or cell from a selective agent (usually an antibiotic)


screenable markers

- genes that give transformed cells an identifiable characteristic to distinguish them from untransformed cell
- do not confer resistance to a selective agent


example of screenable markers

- GFP - fluoresces green when excited by UV light
- luciferase - enzyme that converts energy of ATP into light
- B-gal - convert colorless substrates into colored compounds that can be easily observed

- can be used as reporter genes


reporter genes

- usually attached to regulatory sequences of another gene of interest to test the effects of the regulatory sequences
- products are readily quantifiable
- measure genes activity level