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BSCI330 SPRING > exam 1 nuclear and chromosomal structure > Flashcards

exam 1 nuclear and chromosomal structure Flashcards

1
Q

what defines eukaryotic cells

A

the presence of the nucleus

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2
Q

what is the nucleus bounded by

A

a double membrane (two lipid bilayers)

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3
Q

how does the double membrane of the nucleus communicate with the cytoplasm

A

through large nuclear pores that allow things to go in and out

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4
Q

what does the modification of histones regulate

A

chromatin structure and gene expression

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5
Q

how are prokaryotes and eukaryotes described with kernels

A

eukaryote = “true kernel”

prokaryote = “before kernel”

(kernel beng nucleus)

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6
Q

what does the nucleus contain

A

genetic material of DNA within the double membrane structure, which is continuous with the ER

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7
Q

what is the nuclear lamina

A

supports the nuclear membrane - it’s a fibrous network made of proteins, which provides structural support and allows the nucleus to retain its shape

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8
Q

how is the nucleus compartmentalized

A

into dynamic subdomains - aren’t separated by membranes and can be assembled/disassembled as needed

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9
Q

what is the best understood subdomain of the nucleus

A

the nucleolus - site of ribosome assembly

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10
Q

how is the double membrane actually a single membrane?

A

it’s folded back upon itself to create a double membrane - nuclear pores are where it’s folded over

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11
Q

what occurs if the nuclear lamina lacks lamin A

A

structural support is reduced and the normal organization of chromatin is prevented - affects the ability of cells to divide

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12
Q

what is the nuclear lamina important for

A

organizing chromatin and gene expression

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13
Q

what does the double bilayer of the nuclear membrane present

A

a major barrier to the movement of material between the cytoplasm and nucleus

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14
Q

how is transport between the nucleus and cytoplasm regulated

A

large regulated nuclear pores

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15
Q

what are nuclear pores made up of

A

30 different proteins called nuclearporins

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16
Q

how can large macromolecules and protein complexes travel through nuclear pores

A

active transport

17
Q

what is the DNA in the nucleus of eukaryotic cells divided into

A

23 pairs of chromosomes

18
Q

what does chromatin do

A

condenses linear DNA molecules to fit within the nucleus - changes to regulate gene expression, DNA replication, and cell division

19
Q

what is the basic unit of chromatin

A

the nucleosome

20
Q

what is a histone core composed of

A

two copies of each of the four different histones

21
Q

what do nucleosomes in chromatin look like

A

beads on a string

22
Q

what is between the “beads” of nucleosomes

A

linker DNA

23
Q

what is chromatin condensed into during interphase (when cells aren’t dividing)

A

the 30 nm fiber (formed through interactions between the N-terminal tails of histones in neighboring nucleosomes)

24
Q

what does the linker histone H1 do

A

binds to the outside of each nucleosome and helps condense chromatin

25
Q

what are the two types of interphase chromatin

A

heterochromatin (different chromatin) and euchromatin (true chromatin)

26
Q

what is heterochromatin

A

DNA that is resistant to gene expression (“silences”)

includes centromeres and telomeres

27
Q

what is euchromatin

A

less condensed that heterochromatin and remains accessible to the RNA transcript machinery

28
Q

how can chromatin structure be regulated

A

by covalent modifications to the histone tails

29
Q

what happens when histone tails get modifications

A

can change charge-charge interactions and lead to condensation or de-condensation

30
Q

what is the most highly condensed form of chromatin

A

mitotic chromosomes

31
Q

what is the replication origin

A

the site where DNA duplication is initiated (multiple in eukaryotes)

32
Q

what is the centromere

A

the site of attachment to the mitotic spindle, which allows one copy of each duplicated chromosome to be pulled into each daughter cell during mitosis

33
Q

what is a telomere

A

prevents the ends of chromosomes from being mistaken for broken DNA, and allows for proper duplication of the chromosomes ends

34
Q

out of replication origin, centromere, and telomere, which can be found in prokaryotic cells

A

replication origin

35
Q

what is linker DNA

A

DNA that is NOT wound around histones

36
Q

what does linker histone do

A

binds the the nucleosome on the outside of histone core to help it flex the DNA to help with packing

BSCI330 SPRING (24 decks)

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