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molgen > Ch 7 Lecture (Chromosomes) > Flashcards

Ch 7 Lecture (Chromosomes) Flashcards

1
Q

Chromosome

A

A discrete unit of the genome carrying many genes

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2
Q

Nucleoid

A

The structure in a prokaryotic cell that contains the genome

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3
Q

Chromatin

A

The state of nuclear DNA and its associated proteins during interphase of the eukaryotic cell cycle

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4
Q

Packing Ratio

A

The ratio of the length of DNA to the unit length of the fiber containing it

Ex. 1.4 cm packed into 2 um

Packing ratio: 7000

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5
Q

Capsid

A

The external protein coat of a virus particle

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6
Q

The length of DNA that can be incorporated into a virus is limited by:

A

The structure of the capsid

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7
Q

Two primary methods of constructing capsid with nucleic acids:

A

Assemble the capsid around the nucleic acid

Construct the capsid and load nucleic acid into the empty structure

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8
Q

Natural closed bacterial DNA is:

A

Negatively supercoiled

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9
Q

Ethidium bromide induces:

A

Positive supercoiling

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10
Q

The nucleoid is composed of individual domains, each of which:

A

Can retain their own supercoiled status

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11
Q

Bottlebrush Nucleoid Structure

A

Supercoiled loops emanating from a central core

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12
Q

Nucleoid Associated Proteins (NAPs)

A

Regulators of nucleoid structure and gene expression

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13
Q

Protein HU

A

Histone-like structure

Dimer that plays a role in DNA flexibility

NAP

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14
Q

Protein H-NS

A

Histone-like structure

Preference for AT-rich regions

NAP

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15
Q

how is metaphase DNA arranged

A

as 60kb loops attached to a proteinaceous scaffold

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16
Q

metaphase scaffold

A

a proteinaceous structure in the shape of a sister chromatid pair

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17
Q

during interphase, what does the metaphase scaffold do?

A

fills the entire nucleus and is called the nuclear matrix

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18
Q

how is interphase DNA attached to the nuclear matrix

A

MARs (matrix attachment regions)

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19
Q

MARs are

A

AT rich but do not have a consensus sequence

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20
Q

MARs often contain

A

Cis-acting transcription regulatory sites
5’intron sites
topoisomerase II recognition sites

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21
Q

MARS can also bind to

A

the metaphase scaffold

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22
Q

proteins regulate association of MARs with matrix to regulate

A

transcription

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23
Q

individual chromosomes can only be seen in

A

the M phase

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24
Q

DNA is … times more condensed than chromatin

A

5-10

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25
Q

during interphase, the general mass of chromatin is in the form of

A

euchromatin

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26
Q

where is heterochromatin found

A

nuclear periphery, around nucleolus, and packed as aggregates called chromocenters.

27
Q

open active chromatin

A

euchromatin
actively transcribed genes
highly transcribed and weakly transcribed
minority of genome (20%)

28
Q

closed inactive chromatin

A

euchromatin and heterochromatin
euchromatin is considered quiescent
heterochromatin is considered facultative or constitutive.

29
Q

facultative heterochromatin

A

regulated chromatin
developmentally repressed genes
can be turned on in specific circumstances
barr bodies

30
Q

constitutive heterochromatin

A

“permanently” condensed
replicates late in S phase
repeat rich
reduced recombination frequency
reduced gene density with low levels of transcription

31
Q

chromosome territories

A

distinct regions of the interphase nucleus associated with chromatin from specific chromosomes

32
Q

chromosomes interact at the … of territories

A

periphery

33
Q

homologues are… in the nucleus

A

separated

34
Q

gene dense regions are found in

A

the center of the nucleus

35
Q

active genes are often found at

A

territorial borders

36
Q

heterogeneity of nucleoplasm is facilitated by

A

biomolecular condensate formation

37
Q

transcriptionally active regions of chromatin are actively extended towards the

A

the center of the nucleus and transcription factories

38
Q

what is G-banding

A

when the metaphase spread is digested with trypsin and stained with Giemsa dye

39
Q

In G-banding, what are the g-bands

A

a series of striations that are lower in GC content

40
Q

in G-banding, where are enriched genes loacted

A

interbands

41
Q

in humans, G-bands are approximately how big

A

10^7

42
Q

centromere

A

a constricted region of a chromosome that includes the site of spindle attatchment

43
Q

how are chromosomes attached to the mitotic spindle

A

the kinetochore

44
Q

microtubule organizing center

A

a region from which microtubules emanate
centrosome in animals

45
Q

cohesins

A

proteins that hold sister chromatids together
gradually degrade during anaphase to allow separation

46
Q

how is chromatin structure specified

A

epigenetically

47
Q

centromeres are characterized by

A

centromere specific histone H3 variant
post-translationally modified H2A and H3
often contain satellite DNA rich heterochromatin

48
Q

kinetochore

A

protein structure at centromere that facilitates spindle attachment

49
Q

telomeres are required for

A

protection of linear chromosome ends
extension of chromosomal ends
pairing of homologous chromosomes and recombination

50
Q

why were telomeres created

A

limitations of DNA replication enzymes

51
Q

what enzyme helps maintain telomere length

A

telomerase

52
Q

stability of telomeres is due to

A

the t-loop and shelterin

53
Q

the t-loop is catalyzed by

A

TRF2 protein

54
Q

how is the t-loop made

A

the 3’ repeating unit of the GT rich strand forms a loop by displacing its homologue in an upstream region of the telomere

55
Q

role of telomeres in meiosis

A

telomeres cluster at nuclear membrane immediately preceding coiling of homologous chromosomes
disruption of telomeres leads to defects in recombination

56
Q

proteins involved in influencing telomerase binding

A

Yeast
Rif 1 and 2
Rap 1
Cdc13
Human
TRF 1 and 2
Tin 2
Tpp1
Pot 1
Rap 1

57
Q

shelterin complex

A

TRF 1 and 2
Tin 2
Tpp1
Pot 1
Rap 1

58
Q

how long are telomeres in humans

A

5-15 kb

59
Q

loss of telomeres results in

A

senescence

60
Q

escape from senescence can occur in yeast if

A

telomerase is reactivated
chromosomes are circularized
unequal crossing over

61
Q

cells from multicellular eukaryotes obey the

A

hayflick limit

62
Q

what cells do not obey the hayflick limit

A

stem cells

63
Q

the majority of cancer cells contain

A

reactivated telomerase

molgen (28 decks)

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