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Histology > Ch. 3 - The Nucleus > Flashcards

Ch. 3 - The Nucleus Flashcards

1
Q

Nucleus

A

The command center of the cell
Contains the code for all of a cell’s enzymes and proteins
Stores the genetic information
Largest structure within a cell

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2
Q

What are the components of the nucleus?

A

Nuclear envelope
Chromatin
Nucleolus

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3
Q

Chromatin

A

A mass of DNA and associated proteins

Two types can be distinguished via microscopy, heterochromatin and euchromatin

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4
Q

Nucleolus

A

Specialized subdomain of the nucleus

Contains the genes for pre-rRNA

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5
Q

Nuclear envelope

A

Forms a selectively permeable barrier between nuclear and cytoplasmic components
Two concentric membranes separated by a perinuclear space

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6
Q

Perinuclear space

A

The narrow space between the two concentric membranes of the nuclear envelope
This space and the outer nuclear membrane are continuous with the RER

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7
Q

Nuclear lamina

A

A highly organized meshwork of proteins that is closely associated with the inner nuclear membrane
Stabilizes the nuclear envelope

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8
Q

Lamins

A

Class of intermediate filament proteins that bind to membrane proteins and associate with chromatin in nondividing cells

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9
Q

Nuclear pore complexes

A

Bridge the inner and outer nuclear membranes

Regulate movement of macromolecules between the nucleus and cytoplasm in both directions simultaneously

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10
Q

Nucleoporins

A

Various core proteins of a nuclear pore complex

Eightfold symmetry around the lumen

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11
Q

How is heterochromatin visualized with the light microscope? Electron microscope?

A

Intensely basophilic clumps (light)

Coarse, e- dense material (e-)

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12
Q

How is euchromatin visualized with the light microscope? Electron microscope?

A

Lightly stained basophilic areas (light)

Finely dispersed granular material (e-)

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13
Q

Heterochromatin

A

Highly condensed chromatin
DNA is tightly coiled
Less accessible for transcription

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14
Q

Euchromatin

A

Finely dispersed chromatin
Contains regions of the DNA undergoing active transcription
More prominent in metabolically active cells
Typically more active in protein synthesis

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15
Q

Nucleosome

A

The structural unit of DNA and histones

Has a core of 8 small histones wrapped around DNA of ~150 bp

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16
Q

Barr body

A

A small, dense mass of heterochromatin present in females but not in males
Aka “sex chromatin”
One of the two X chromosomes

17
Q

Chromatid

A

Each long DNA double helix and its associated proteins

18
Q

Chromosome

A

Two chromatids held tougher by complexes of cohesin proteins

19
Q

The members of each chromosomal pair are called _______ because, although from different parents, they contain allele of the same genes.

A

homologous

20
Q

Cells of most tissues (somatic cells) are considered _______ because they contain pairs of chromosomes.

A

diploid

21
Q

Diploid cell are referred to as _______.

A

2n

22
Q

Germ cells are _______, with half the diploid number of chromosomes, each pair having been separated during meiosis.

A

haploid

23
Q

Germ cells

A

Sperm cells and mature oocytes

Haploid

24
Q

Karotyping

A

Chromosomal analysis where the condensed chromosomes of one nucleus may be photographed by light microscopy and rearranged to produce a karotype in which stained chromosomal bands can be analyzed

25
Q

What causes the intense basophilia of the nucleolus?

A

Densely concentrated rRNA that is transcribed, processed, and complexed into ribosomal subunits in the nucleoli

26
Q

Cell cycle

A

Regular sequence of events that result in new cells

27
Q

What are the four distinct phases of the cell cycle?

A
  1. G1 phase (part of interphase)
  2. S phase (part of interphase)
  3. G2 phase (part of interphase)
  4. M-phase (and cytokinesis)
28
Q

M phase

A

Cell division that results in clones

29
Q

G1 phase

A

The time gap between mitosis and DNA replication
Cellular content is duplicated, not chromosomes
Period of active RNA and protein synthesis
Cell volume, reduced in half by mitosis, is returned to normal volume

30
Q

S phase

A

Synthesis phase
The period of DNA synthesis
Chromosome duplication
Histone synthesis

31
Q

G2 phase

A

The gap between DNA duplication and the next mitosis
Cell grows and prepares for mitosis by accumulating proteins needed
Checks for errors

32
Q

What are the phases of M phase?

A
  1. Mitosis
  2. Prophase
  3. Metaphase
  4. Anaphase
  5. Telophase
33
Q

G0 phase

A

Postmitotic cells that stop differentiating and specialize
In a state of arrest
Stem cells live in this phase

34
Q

Mitogens or Growth factors

A

Protein signals from the extracellular environment that activate cycling in post mitotic G0 cells
Bind to cell surface receptors and trigger a cascade of kinase signaling in the cells

35
Q

Prophase

A

Nucleolus disappears and chromosomes are visible

At the centromere, kinetochores serve as a site for microtubule attachment

Histology (14 decks)

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