The Nucleus

Front 1

How are the nucleoplasm and the cytoplasm seperated?

Back 1

by the nuclear envelope, a double set of membranes with a narrow perinuclear space;
the outer membrane binds ribosomes and is continuous with the RER.

Front 2

The nuclear enevelope is penetrated by...

Back 2

nuclear pore complexes , large assemblies of nucleoporins with eightfold symmetry through which proteins and protein-RNA complexes move in both directions.

Front 3

How is the nuclear envelope supported internally?

Back 3

by a meshwork, the nuclear lamina, composed of intermediate filament subunits called
lamins.

Front 4

What is chromatin?

Back 4

Chromatin is the combination of DNA and its associated proteins

Front 5

How does chromatin stain?

Back 5

Depends...

Chromatin with DNA that is active in transcription stains lightly and is called euchromatin ; inactive chromatin stains more darkly and is
called heterochromatin .

Front 6

DNA molecules wrap around what?

Back 6

around complexes of basic proteins
called histones to form nucleosomes , producing a structure resembling beads on a string.

Front 7

What does the extra-X-chromosome in females form?

Back 7

A Barr Body

Front 8

What is the nucleolus?

Back 8

The nucleolus is a very basophilic or electron-dense area of chromatin localized where rRNA transcription and ribosomal subunits
assembly occur.

Front 9

Describe the nucleolus

Back 9

By TEM, an active nucleolus is seen to have fibrous and granular parts where rRNA forms and ribosomal subunits are assembled,
respectively.

Front 10

What is the cell Cycle?

Back 10

The cell cycle is the sequence of events that controls cell growth
and division

Front 11

G1 phase

Back 11

the longest part of the cycle, begins immediately
after
mitosis and includes all preparations for DNA replication.

Front 12

S Phase

Back 12

The period of DNA (and histone) synthesis is the S phase.

Front 13

G2 Phase

Back 13

In a short G2 phase the cell prepares for division during mitosis (M).

Front 14

What controls cell cycling ?

Back 14

controlled by the sequential appearance of key
cytoplasmic proteins, the cyclins, which bind cyclin-dependent kinases (CDKs).

Front 15

What do CDKs do?

Back 15

They phosphorylate and activate the enzymes and transcription factors whose functions characterize each phase of the cell cycle.

Front 16

How is the progress in cell cycles monitored?

Back 16

Progress through the cell cycle stages is monitored at checkpoints,
including the G1 restriction point; only when each phase’s activities are completed are the cyclins changed to trigger those of the
next phase.

Front 17

What are the divisions of Mitosis. In order?

Back 17

Stages of mitotic cell divisions include prophase, when chromosomes
condense, the nuclear envelope disassembles, and the microtubular spindle forms; metaphase, when chromosomes are
aligned; anaphase, when they begin to separate toward the two centrosomes; and telophase, when nuclear envelope re-forms
around the separated chromosomes.

Front 18

What is cytokinesis?

Back 18

cell cleavage into two daughter
cells by a contractile ring of actin filaments and myosin.

Front 19

How do stem cells divide?

Back 19

Stem cells occur in all tissues with rapid cell turnover; they divide
slowly in an asymmetric manner, with one daughter cell remaining
a stem cell and one becoming committed toward differentiation.

Front 20

What is Meiosis?

Back 20

Meiosis is the process by which two successive cell divisions produce
cells called gametes containing half the number of chromosomes
found in somatic cells.

Front 21

What is unique about prophase in meiosis?

Back 21

Prophase of the first meiotic division is a unique, extended period in
which homologous chromosomes pair and undergo genetic recombination
during the process called synapsis.

Front 22

What happens after recombination in meiosis?

Back 22

Synaptic pairs separate toward two daughter cells at the first meiotic
division.

Front 23

Is there an S phase in Meiosis after the 1st division?

Back 23

The second meiotic division occurs with no intervening S phase and
separates the sister chromatids into two final cells that are haploid.

Front 24

What is apoptosis?

Back 24

Apoptosis is the process by which redundant or defective cells are
rapidly eliminated in a manner that does not provoke a local inflammatory
reaction in the tissue.

Front 25

What controls apoptosis?

Back 25

cascade of events controlled by the Bcl-2 family
of proteins regulating the release of death-promoting factors from
mitochondria.

Front 26

What are the "death promoting factors" from mitochondria?

Back 26

Cytochrome c from mitochondria activates cytoplasmic proteases
called caspases, which degrade proteins of the cytosol, cytoskeleton,
and cell membrane.

Front 27

What happens to DNA during apoptosis?

Back 27

Endonucleases are activated, which degrade all nuclear DNA

Front 28

What happens to the "remains" of the cell after apoptosis?

Back 28

cell breaks into many small apoptotic bodies
that undergo phagocytosis by neighboring cells.

Front 29

Does apoptosis trigger inflamation?

Back 29

Apoptosis occurs rapidly, with little or no release of proteins that would trigger inflammation, unlike the death of injured cells by necrosis that typically induces local inflammation.