Lecture 5 Reading Flashcards Preview

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Flashcards in Lecture 5 Reading Deck (41):
1

Mitotic chromosomes

Highly condensed chromosomes in a dividing cell

2

What three types of specialized nucleotide sequences in DNA contorl replication, separation and partition into daughter cells

DNA replication origin
Centromere
Telomere

3

Replication origin

Nucleotide sequence
The location at which duplication of DNA begins

4

Centromere

Nucleotide sequence
Allows one copy of each duplicated and condensed chromosome to be pulled into a daughter cell when a cell divides

5

Kinetochore

Protein complex forms at centromere and attaches duplicated chromosomes to the mitotic spindle so they can be pulled apart

6

Telomere

The ends of a chromosome
Contain repeated nucleotide sequences that enable ends of chromosomes to be efficiently replicates
Form structures that protect the end of the chromosome from being mistaken by the cell for a broken DNA molecule that needs repair

7

Proteins that bind to dna to form eukaryotic chromosomes 2

Histones
Non histone chromosomal proteins

8

Chromatin

Complex of histone and non histone chromosomal protein with nuclear dna if eukaryotic cells

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Nucleosome

Most basic level of chromosome packing

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Linker DNA

Exposed dna between nucleosome core particles

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Histone octamer

Forms a protein core around which the double stranded DNA is wound

12

Nucleosomes repeat at intervals of

About 200 nucleotide pairs

13

Epigeneric inheritance

A form of inheritance that is superimposed on the genetic inheritance based on DNA

14

Two types of chromatin

Heterochromatin - highly condensed
Euchromatin - not as condensed

15

Position effect

Chromosome breakage and rejoining that translocate normally euchromatic DNA into the neighborhood of heterochromatin

16

Position effect variegation

Once a heterochromatin condition is established on a piece of chromatin, it tends to be stably inherited by all of the cell's progeny

17

How is DNA packaged

DNA tightly wrapped in a left handed coil of 1.7 turns. All four of the histones that make up core of nucleosome are small proteins. They share a structural motif known as the histone fold, which is formed from three alpha helices connected by two loops.

18

How large is interface between DNA and histones

142 h bonds formed between DNA and histone core in each nucleosome, half of these bonds form bet. The amino acid backbone of the histones and the sugar phosphate backbone of dna. Hydrophobic interactions and salt linkages also hold dna and protein together in nucleosome. More than one fifth of a, acids in histones is lysine or arginine, positive charges neutralize dna backbone which is negative.

19

Chromatin remodeling complexes

Include a subunit that Hydrolyzes ATP. Subunit binds to protein core of nucleosome and to double stranded dna that winds around it. ATP hydrolysis releases energy to move Dna and changes structure of nucleosome.

20

Linker stone

Histone H1 larger than individual core histones. Single h1 binds to each nucleosome contacting dna and protein, and changing path of dna as it exits from the nucleosome.

21

How are core histones covalently modified

Acetylation of lysines, mono, di and trimethylation of lysines, and phosphorylation of serines. Occur on unstructured n-terminal histone tails that protrude from nucleosome. Are reversible.

22

Histone acetyl transferase

Adds acetyl groups to lysines

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Histone deacetylate complexes

Remove acetyl groups from lysines

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Histone methyl Transferases and histone demethylases

Add and remove methyl groups

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What does acetylation of lysine cause

Loosens chromatin structure, removes lysine's positive charge and affinity of tails for adjacent Nucleosomes,

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Most profound effect of histone modification

Their ability to recruit specific other proteins to the modified stretch of chromatin. Recruited proteins act with modified histones to determine how and when genes will be expressed, as well as other chromosomal functions.

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Histone variants

Histones extra of standard core histones

28

When are major histones made? Variants?

S phase. Interphase.

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Histone code

Combination known to have specific meaning for the cell in the sense that they determine how and when DNA in Nucleosomes is to be accessed

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Reader complex

Protein domains linked together as modules in a single large protein or protein complex, which thereby recognizes a specific combo of histone modifications

31

Lampbrush chromosomes

Stiff and enormously extended chromosomes in growing amphibians. Paired in preparation for meiosis, clearly visible in light microscope.

32

Polytene cells of flies

Fruit fly drosophila
Multiple cycles of dna synthesis make cell unusually large. Polyploid cells.

33

Polytene chromosomes

Copies of each chromosome are aligned side by side to create thse giant chromosomes

34

What happens to a gene when it is highly expresses

It's position in interior of nucleus changes

35

Nucleolus

Ribosome unit formation site

36

Canal bodies and inter chromatin granule clusters

Organelles inside nucleus of plant and animal cells

37

Nuclear matrix or scaffold

Insoluble material left in nucleus after a series of biochemical extraction steps

38

Purposes of compaction during mitosis

When condensation complete, sister chromatids have been disentangled
Compaction of chromosomes protects the relatively fragile dna molecules from being broken as they are pulled apart

39

When does condensation of interphase chromosomes into mitotic chromosomes begin

In early M phase. Connected with progression of cell cycle. Gene expression shuts during M phase.

40

Cohesive and condensins

Aid compaction of chromosomes

41

Karyotype

The display of 46 human chromosomes at mitosis