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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
during interphase, the general mass of chromatin is in the form of
euchromatin
26
where is heterochromatin found
nuclear periphery, around nucleolus, and packed as aggregates called chromocenters.
27
open active chromatin
euchromatin actively transcribed genes highly transcribed and weakly transcribed minority of genome (20%)
28
closed inactive chromatin
euchromatin and heterochromatin euchromatin is considered quiescent heterochromatin is considered facultative or constitutive.
29
facultative heterochromatin
regulated chromatin developmentally repressed genes can be turned on in specific circumstances barr bodies
30
constitutive heterochromatin
"permanently" condensed replicates late in S phase repeat rich reduced recombination frequency reduced gene density with low levels of transcription
31
chromosome territories
distinct regions of the interphase nucleus associated with chromatin from specific chromosomes
32
chromosomes interact at the ... of territories
periphery
33
homologues are... in the nucleus
separated
34
gene dense regions are found in
the center of the nucleus
35
active genes are often found at
territorial borders
36
heterogeneity of nucleoplasm is facilitated by
biomolecular condensate formation
37
transcriptionally active regions of chromatin are actively extended towards the
the center of the nucleus and transcription factories
38
what is G-banding
when the metaphase spread is digested with trypsin and stained with Giemsa dye
39
In G-banding, what are the g-bands
a series of striations that are lower in GC content
40
in G-banding, where are enriched genes loacted
interbands
41
in humans, G-bands are approximately how big
10^7
42
centromere
a constricted region of a chromosome that includes the site of spindle attatchment
43
how are chromosomes attached to the mitotic spindle
the kinetochore
44
microtubule organizing center
a region from which microtubules emanate centrosome in animals
45
cohesins
proteins that hold sister chromatids together gradually degrade during anaphase to allow separation
46
how is chromatin structure specified
epigenetically
47
centromeres are characterized by
centromere specific histone H3 variant post-translationally modified H2A and H3 often contain satellite DNA rich heterochromatin
48
kinetochore
protein structure at centromere that facilitates spindle attachment
49
telomeres are required for
protection of linear chromosome ends extension of chromosomal ends pairing of homologous chromosomes and recombination
50
why were telomeres created
limitations of DNA replication enzymes
51
what enzyme helps maintain telomere length
telomerase
52
stability of telomeres is due to
the t-loop and shelterin
53
the t-loop is catalyzed by
TRF2 protein
54
how is the t-loop made
the 3' repeating unit of the GT rich strand forms a loop by displacing its homologue in an upstream region of the telomere
55
role of telomeres in meiosis
telomeres cluster at nuclear membrane immediately preceding coiling of homologous chromosomes disruption of telomeres leads to defects in recombination
56
proteins involved in influencing telomerase binding
Yeast Rif 1 and 2 Rap 1 Cdc13 Human TRF 1 and 2 Tin 2 Tpp1 Pot 1 Rap 1
57
shelterin complex
TRF 1 and 2 Tin 2 Tpp1 Pot 1 Rap 1
58
how long are telomeres in humans
5-15 kb
59
loss of telomeres results in
senescence
60
escape from senescence can occur in yeast if
telomerase is reactivated chromosomes are circularized unequal crossing over
61
cells from multicellular eukaryotes obey the
hayflick limit
62
what cells do not obey the hayflick limit
stem cells
63
the majority of cancer cells contain
reactivated telomerase

MOLGEN (28 decks)

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