Ch. 3 - The Nucleus Flashcards Preview

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Flashcards in Ch. 3 - The Nucleus Deck (35):
1

Nucleus

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

2

What are the components of the nucleus?

Nuclear envelope
Chromatin
Nucleolus

3

Chromatin

A mass of DNA and associated proteins
Two types can be distinguished via microscopy, heterochromatin and euchromatin

4

Nucleolus

Specialized subdomain of the nucleus
Contains the genes for pre-rRNA

5

Nuclear envelope

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

6

Perinuclear space

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

7

Nuclear lamina

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

8

Lamins

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

9

Nuclear pore complexes

Bridge the inner and outer nuclear membranes
Regulate movement of macromolecules between the nucleus and cytoplasm in both directions simultaneously

10

Nucleoporins

Various core proteins of a nuclear pore complex
Eightfold symmetry around the lumen

11

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

Intensely basophilic clumps (light)
Coarse, e- dense material (e-)

12

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

Lightly stained basophilic areas (light)
Finely dispersed granular material (e-)

13

Heterochromatin

Highly condensed chromatin
DNA is tightly coiled
Less accessible for transcription

14

Euchromatin

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

15

Nucleosome

The structural unit of DNA and histones
Has a core of 8 small histones wrapped around DNA of ~150 bp

16

Barr body

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

17

Chromatid

Each long DNA double helix and its associated proteins

18

Chromosome

Two chromatids held tougher by complexes of cohesin proteins

19

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

homologous

20

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

diploid

21

Diploid cell are referred to as _______.

2n

22

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

haploid

23

Germ cells

Sperm cells and mature oocytes
Haploid

24

Karotyping

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

What causes the intense basophilia of the nucleolus?

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

26

Cell cycle

Regular sequence of events that result in new cells

27

What are the four distinct phases of the cell cycle?

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

28

M phase

Cell division that results in clones

29

G1 phase

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

S phase

Synthesis phase
The period of DNA synthesis
Chromosome duplication
Histone synthesis

31

G2 phase

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

32

What are the phases of M phase?

1. Mitosis
2. Prophase
3. Metaphase
4. Anaphase
5. Telophase

33

G0 phase

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

34

Mitogens or Growth factors

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

Prophase

Nucleolus disappears and chromosomes are visible
At the centromere, kinetochores serve as a site for microtubule attachment