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49 Cards in this Set

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What is the typical diameter of a nucleus?
5-10 microns
do nuclei stain acidophilic or basophilic with an H&E stain?
basophilic
which, euchromatin or heterochromatin, shows DNA that is actively being transcribed?
euchromatin
why is heterochromatin darkly stained?
the DNA is condensed because it is not being actively transcribed.
levels of what can give you clues about the activity level of the nucleus, and hence, the cell at large?
euchromatin and heterochromatin
Do the nucleoli stain basophilic or acidophilic in an H&E stain?
basophilic (blue/purple)
what two processes occur in the nucleoli?
1) rRNA synthesis and 2) ribosomal subunit assembly
How many membranes envelop the nucleus of the cell? What other organelle also has this number of membranes?
2 membranes; mitochondrion
what is the name of the space between the outer and inner membranes in a nucleus?
perinuclear cisterna
the outer nuclear membrane is continuous with which organelle in the cell?
rough endoplasmic reticulum
the perinuclear cisterna is continuous with which part of the extranuclear cell?
the lumen of the RER.
True or False, the outer nuclear membrane could be studded with ribosomes?
True
What is the name for the channels present in the nuclear envelope?
Nuclear pores
how many histones compose a nuclosome?
8 (2 of each of 4 types of histones)
what are the names for the histones that participate in the organization of DNA into nucleosomes?
H2a, H2b, H3, H4
which proteins are involved in assembling the nucleosomes into larger 30nm units? What is the name for these units?
H1 histones and other acidic proteins; solenoid fibers
what are the main components of the nucleoskeleton
histones, acidic proteins, and other structures which help to organize the chromatin (DNA) into supercoils.
what is the width measurement of a nucleosome
11nm
which structure supports the nucleur envelope on its internal surface?
nuclear fibrous lamina
nuclear lamins are found where and are composed of which type of cytoskeleton?
on the inner surface of the nuclear envelope; intermediate filaments
what are the name of 3 lamins found in the fibrous lamina in the nucleus?
Lamins A, B, and C
in which 3 activities are lamins A, B, and C involved?
1) attachment of chromatin to the nuclear envelope, 2)structural integrity of the envelope, and 3)envelope reassembly following nuclear envelope breakdown during mitosis.
breakdown of the nuclear envelope in mitosis is triggered by the phosphorylation of which nuclear proteins?
lamins
dephosphorylation of nuclear lamins has what effect on the integrity of the nucleus
it triggers reassembly of the nuclear envelope
the nuclear pore complexes (NPC) are composed of approximately how many proteins
approximately 100 proteins
what is the name for the proteins which make up the nuclear pore complex (NPC) and make a channel for transport of material into and out of the nucleus?
nucleoporins
how are small molecules (i.e. <40kD) granted entry to the nucleus?
they diffuse freely
what two important factors are key in getting large material into the nucleus, through the pores?
1) import and export signals and 2) chaperons molecules
what is an NLS (nuclear localization signal)?
a peptide signal on a protein that signals the nucleus as the protein's destination
which specific class of proteins are important in recognizing the NLS and facilitation entry into the nucleus for large material? These proteins are part of which larger class of proteins?
Importins; Chaperons proteins
Importins interact with which two things?
the NLS on the protein entering the cell and the pore fibrils.
True or false, the nucleolus has a single membrane while the nucleus envelope is composed of 2 membrane layers.
False. The nucleolus has no mebrane.
what is the NOR? which organelle does it compose?
Nuclear organizing regions; nucleolus.
how many chromosomes contain rDNA?
10
True or False: Red Blood Cells have large nuclei.
False. They are anucleate.
when looking at tumorous cells versus normal, healthy cells, what is an important ratio to consider
nucleus:cytoplasm. Should be less nucleus than cytoplasm, on average.
in which area can you normally find constitutive heterochromatin?
along the inner nuclear membrane (next to fibrous lamina)
which stains lighter: euchromatin or heterochromatin?
euchromatin
what are the two classes of heterochromatin?
constitutive and facultative
which type of heterochomatin is always condensed and very rarely transcribed?
constitutive
Does an abundance of euchromatin mean a cell is very active or dormant?
active
what is the name for the DNA in between nucleosomes?
linker DNA
protein scaffolding around which chromatids are wound is composed of what kind of proteins
acidic proteins
Fill in the Blank: As DNA condensation increases, transcriptional activity ______.
decreases.
while the rRNA is transcribed in the nucleolus, where is this rRNA combined with proteins to form ribosomal subunits?
in the nucleolus, too.
If a cell has large or multiple nucleoli, what does that say about the cell?
the cell is very active
what is contained in the fibrillar center of the nucleolus?
rDNA not being transcribed
what is contained in the dense fibrillar zone?
rDNA being transcribed
What occurs in the granular zone of the nucleolus?
ribosome subunits are processed and packaged