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Cellular and Molecular Biology > Exam 2: Ch 6 Organization of Eu Chromo and Functional Elements > Flashcards

Exam 2: Ch 6 Organization of Eu Chromo and Functional Elements Flashcards

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1
Q

the packing of DNA is crucial

A

to cell architecture

to prevent tangles in long DNA during cell division

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2
Q

histones

A

abundant nuclear proteins that compact and organize chromosomal DNA

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3
Q

chromatin

A

complex of histones and DNA (1/2ea)

dispersed in interphase

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4
Q

further folding and compaction of chromatin during mitosis produces…

A

visible metaphase chromosomes

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5
Q

the structural organization of _______ allows vast DNA length to be compacted into the microscopic constraints of the nucleus

A

chromatin

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6
Q

5 major types of histone proteins

A

H1, H2A, H2B, H3, H4

rich in pos charged aa that interact with neg charged phosphate on DNA

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7
Q

extracted chromatin appearance depends on

A

salt concentration

low = beads on a string

physiological = condensed fiberlike form 30nm in diameter

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8
Q

beads on a string

A

nucleosomes connected by linker DNA

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9
Q

nucleosomes

A

primary structural units of chromatin

about 10nm in diameter

less susceptible to nuclease digestion than linker DNA

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10
Q

structure of a histone

A

DNA wrapped around octamer histone protein core

2 copies of each histone (not H1) into a disk like structure

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11
Q

when is DNA assembled into nucleosomes

A

during cell replication after the replication fork passes

uses histone chaperones

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12
Q

structure of 30nm fiber

A

chromatin zig-zag ribbon

two strands of stacked nucleosomes wound into a left handed double helix

contains H1

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13
Q

30nm fiber purpose

A

chromatin in chromosomal regions not being transcribed or replicated

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14
Q

modifications of _____ ______ control chromatin condensation and function

A

histone tails

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15
Q

histone tail

A

flexible n-terminus and C-terminus in H2A and B extending from histone octamer core

required for chromatin to condense from beads on a string to 30nm fiber

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16
Q

histone tail modification

A

post-translational modifications like acetylation, methylation, phosphorylation, and ubiquitination

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17
Q

histone code

A

the different combinations of tail modification

alter binding sites on chromatin-associated proteins

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18
Q

histone acetylation

A

tail lysines undergo reversible acetylation by enzymes acting on N-terminus

acetylation neutralizes lysine’s positive charge –> beads on a string (increases transcription and replication)

correlated with increased chromatin digestion by nucleases

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19
Q

histone methylation

A

prevents acetylation to maintain positive charge on lysine

makes chromatin less available

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20
Q

heterochromatin

A

dark staining condensed regions of chromatin

remains compacted after mitosis

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21
Q

examples of heterochomatin

A

centromeres, telomeres, transcriptionally inactive genes

22
Q

euchromatin

A

light staining loose chromatin

most transcribed regions of DNA

23
Q

histone code of modified aas in tails is “read” b proteins that…

A

bind to modified tails and promote condensation or decondensation

forms open or closed chromatin structures as judged by their sensitivity to DNase I digestion

24
Q

proteins that read histone code have a _______

A

chromodomain that binds histone tails when they’re methylated at specific lysines

25
Q

example of a histone code reading protein

A

HP1 heterochromatin protein I

has a 2nd domain called chromoshadow domain that helps spread methylation into heterochromatin

26
Q

bromodomain

A

binds to acetylated histone tails in euchromatin

27
Q

TFIID

A

a transcription factor with a bromodomain

histone acetylase activity

28
Q

x-chromosome inactivation in females

A

epigenetic gene control through repression by heterochromatin

half of cells have inactive Xmom and inactive Xdad

29
Q

dosage compensation

A

process that ensures cells of females express same level of proteins encoded on x-chromosomes as cells as males who only have 1

30
Q

Polycomb in dosage compensation

A

binds methylated histone tails and contains histone methyl transferase activity

31
Q

epigenetic process

A

affects expression of specific genes and is inherited by daughter cells w/o being result of a change in DNA sequence

32
Q

nonhistone proteins organize….

A

long chromatin loops

scaffold associated regions (SARs) or matrix attachment regions (MARs)

33
Q

SARs/MARs

A

located at bases of DNA loops

found between transcription units

insulate neighboring genes

34
Q

insulators

A

DNA sequences that separate transcription units from each other

35
Q

can proteins regulating transcription of one gene influence the transcription of a neighboring gene separated by an insulator?

A

no

36
Q

structural maintenance of chromosome proteins (SMCs)

A

hold bases of chromatin loops in place in interphase

nonhistone proteins that a crucial for maintaining structure of condensed chromatin in mitosis

37
Q

chromonema fiber

A

100-130nm fiber condenses during prophase

38
Q

middle prophase chromatid

A

200-250nm structure made from a chromonema fiber

folds into 500-750nm chromatids observed in metaphase

39
Q

interphase and metaphase chromosomes contain…

A

proteins other than histones that regulate transcription and replication

transcription factors in interphase

high mobility group proteins (HMG) assist binding of TFs

40
Q

each metaphase chromosome consists of two sister _____ that are linked at the centromere

A

chromatids

41
Q

karyotype

A

number, sizes and shapes of the metaphase chromosomes

different for each species

human: 22 autosomes 1 pair of sex chromosomes

42
Q

FISH

A

chromosomes painting that differentiates chromosomes os similar size and shape

probes specific for sites scattered along length of chromosome

43
Q

how does FISH work

A

probes labeled with different fluorescent dyes are hybridized to chromosomes

observed with fluorescence microscope

44
Q

what is FISh used for

A

detect abnormal number of chromosomes, translocations

finer structure analysis to reveal deletions or duplications or chromosomal regions

reveal evolution of chromosomes

45
Q

conserved synteny

A

genes occurring in the same order on a chromosome in 2 different species

46
Q

polytene chromosome

A

enlarged interphase chromosomes with a large number of reproducible well-demarcated bands

salivary glands of fruit flies

precisely locate specific DNA sequences, translocations, and inversions (immunostaining)

47
Q

3 functional elements required for replication and correct segregation

A

replication origins where DNA polymerase + other proteins initiate synthesis

centromere (proper segregation)

telomeres

48
Q

kinetochore

A

complex protein structure that assembles at centromeres and uses mitotic spindle fibers

49
Q

telomere

A

repeat sequence TTAGGG at end of chromosomes to prevent shortening

lagging strand not replicated by DNA polymerase in its entirety so lose end of chromo

50
Q

telomerase

A

specialized form of reverse transcriptase that carries an internal RNA template to direct DNA synthesis

adds telomeres to ends of chromosomes

51
Q

telomerase is active/inactive in…

A

active: cancer, germ/stem cells
inactive: cells of adult tissues that replicate a limited number of times or never again (postmitotic)

Cellular and Molecular Biology (34 decks)

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