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L 211 > exam 2 info > Flashcards

exam 2 info Flashcards

1
Q

what is a packaging mechanism for chromosomes

A

chromatin

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2
Q

what are chromosomes

A

stretches of compressed DNA

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3
Q

whats chromatin

A

specific proteins interacting with DNA to form nucleoprotein

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4
Q

about how long is human DNA in meters

A

2 meters (6’6”)

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5
Q

how is the nucleoid formed?

A

specific proteins interact with DNA

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6
Q

what kind of fold compact is DNA in a nucleus

A

10,000 fold compaction

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7
Q

what are histones

A

small basic proteins

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8
Q

how would histones be viewed under microscopy

A

beads on a string. the beads being nucleosome

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9
Q

what is the nucleosome

A

basic unit of eukaryotic chromatin, formed from about 8 histones wrapped by DNA

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10
Q

what is chromatin remodeling

A

enzymes that use ATP to alter chromatin structure

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11
Q

what 3 mechanisms are site exposure models

A

repositioning
ejection
unwrapping

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12
Q

what 2 mechanisms are altered composition

A

dimer exchange

dimer ejection

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13
Q

closed chromatin prevents what

A

prevents proteins to bind to DNA

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14
Q

open chromatin allows what

A

provides access to specific DNA sequences

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15
Q

what is going on if a a chromatin is depleted of nucleosomes

A

have active regions of the genome

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16
Q

what goes on during nuclease digestion

A

digestion removes linker DNA between nucleosomes and destroys it with MNase

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17
Q

what is endonuclease activity

A

cleavage of DNA

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18
Q

what is exonuclease activity

A

chewing of DNA

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19
Q

how many bases of DNA typically wrap around nucleosomes

A

150

20
Q

what is a centromere

A

section of chromosomes responsible for cell’s ability to properly segregate sister chromatids during cell division

21
Q

how are nucleosomes arranged in chromatid

A

biologists don’t really know

22
Q

why is chromatin modification important

A

recruits proteins to chromatin an regulating chromatin-based processes

23
Q

how are proteins modified

A

through covalent attachments of various functional groups to specific amino acids

24
Q

what can be attached to a proteins during modification

A

small chemical groups
lipids
small polypeptides

25
Q

what occurs during proteolysis

A

split of an inactive precursor protein into an active form

26
Q

what types of protein modifications are there

A

acetylation
methylation
phosphorylation

27
Q

what are nucleosomes

A

8 histones proteins wrapped by about 147 base pairs

28
Q

how are histones bonded

A

covalently

29
Q

nomenclature structure of histones

A

name of histone +
residue one letter code +
residue number +
modification

30
Q

histone lysine is acetylated by

A

acetyltransferases

31
Q

histone lysine is deacetylated by

A

deacetylases

32
Q

what occurs during acetylation of histone lysine

A

neutralizes the postitive charge of lysine’s side chain

33
Q

when does lysine acetylation also occur

A

in citric acid cycle

34
Q

functions of protein lysine acetylation

A 
regulate interactions of histones with DNA
changes interaction partners 
changes cellular localization 
controls cytoskeleton dynamics 
controls cell growth
35
Q

histone lysine is catalyzed by? and removed by?

A

catalyzed- methyltransferases

removed- demethylases

36
Q

lysine can have how many methyl groups

A

up to 3, and doesn’t ever change the charge

37
Q

whats the purpose of histone lysine methylation

A

creates binding sites for many proteins (ex: polycomb)

38
Q

what are hox genes and their purpose

A

organized linear structures that specify the body plan in multicellular organisms. They must be expressed in the correct environments and silenced everywhere else for proper development

39
Q

mutations in the polycomb gene result in

A

ectopic (abnormal location) sex combs

40
Q

what are ectopic sex combs

A

a gene is not correctly placed, causing sex spots (on legs) in places they shouldn’t be

41
Q

what is a homeotic phenotype

A

mutational phenomenon of homeostasis, where an organ turns into another

42
Q

mutations in the trihorax gene results in

A

sex combs are significantly reduced

43
Q

whats the function of the polycomb-group protein

A

repress gene expression (transcription) through chromatin based mechanism

44
Q

what is Zeste (E(z))?

A

its a polycomb-group protein enhancer, that catalyzes H3K27me3, through methylation

45
Q

function of Trithorax-group proteins

A

activate gene expression

46
Q

what does Trithorax do and catalyze?

A

its a histone methyltransferase, that catalyzes H3K4me3 and H3K27

L 211 (12 decks)

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