Ch 3 Flashcards
The nucleus is a ______________ that contains the______ (genetic
information) in eukaryotic cells.
- membrane-limited compartment
- genome
what does the nucleus contain?
machinery for DNA replication and RNA transcription and processing.
what does the nucleus of a nondividing cell (interphase cell) consists of?
- chromatin
-barr body - nucleolus
- nuclear envelope
- nucleoplasm
What is chromatin?
A complex of DNA and proteins, responsible for the basophilia of the nucleus.
chromatin contains __________
equal mass of various nuclear proteins including histones
what are the two forms that chromatin is organized into?
euchromatin (dispersed, lightly staining, active) and heterochromatin (condensed, densely staining, mostly inactive).
Heterochromatin can be
- constitutive (genetically inactive, repetitive sequences)
- facultative (location varies, can undergo active transcription in some cells)
heterochromatin stains with what basic dye?
hematoxylin
where is Constitutive heterochromatin found near?
centromeres and telomeres
what can Facultative heterochromatin form
barr bodies
Euchromatin is __________ in the light microscope. It is present within the___________ in the “clear” areas between and around the heterochromatin. In routine electron micrographs, there is no sharp delineation between euchromatin and heterochromatin; both have a granular, filamentous appearance, but the euchromatin is less tightly packed
- not evident
- nucleoplasm
where is marginal chromatin found?
at the periphery of the nucleus.
what are karyosomes?
discrete bodies of chromatin found throughout the nucleus.
what is associated with the nucleolus?
Nucleolar-associated chromatin
what are the smallest units of chromatin?
nucleosomes
what are nucleosomes?
macromolecular complexes of DNA and histones.
what does nucleosomes consist of?
DNA coiled around a core of eight histone molecules.
Further folding of chromatin forms a ___________, which is further organized into loop domains.
30-nm chromatin fibril
In dividing cells, chromatin condenses to form _________
chromosomes
Each chromosome is made of two___________ joined at the centromere.
chromatids
where are telomeres located at?
at the ends of chromosomes. Cell aging. Telomerase present in cancer cells which is involved in making them immortal.
Human cells contain 23 homologous pairs, including 22 pairs of________ and one pair of sex chromosomes (XX in females, XY in males).
autosomes
what are karyotypes used for?
to sort chromosomes based on size, shape and fluorescent color.
metaphase spread
contains some individual chromosomes as well as other chromosomes that may not be well spread out, i.e., overlapping or touching
In the past, chromosomes were routinely stained with ____________; however, with the recent development of in situ hybridization techniques, the _______________ procedure is now more often used to visualize a chromosomal spread.
- Giemsa stain
- fluorescent in situ hybridization (FISH)
- Red box shows translocation
what is a barr body
Some chromosomes are repressed in the interphase nucleus and exist only in the tightly packed heterochromatic form.
one X chromosome of the female is an example of such a chromosome (Barr body) and can be used to identify the sex of a fetus.
what does a barr body look like?
Drumstick appendage
what is the nucleolus?
A non-membranous region within the nucleus,
the site of rRNA synthesis and initial ribosomal assembly.
the nucleolus contains DNA loops of chromosomes containing………
- rRNA genes
- RNA polymerase I
- transcription factors
what are the three morphologically distinct regions of the nucleolus?
- fibrillar centers
- fibrillar material
- granular material
The network formed by the granular and the fibrillar materials is called the_______
nucleolonema
what is the nucleolus involved in?
regulation of the cell cycle
the nucleolus contains ________ a protein that regulates the cell cycle.
nucleostemin
The presence of ___________ in malignant cells suggests that it could play a role in their _____________
- nucleostemin
- uncontrolled proliferation
The nucleolus stains intensely with ________ and______ dyes and metachromatically with______ dyes
- hematoxylin
- basic
- thionine
what does the nuclear envelope look like?
it has a double membrane system surrounding the nucleus
nuclear envelope
The outer membrane is ____
The inner membrane is ______
- continuous with the rER and studded with ribosomes.
- adjacent to the nuclear lamina.
what does the nuclear envelope contain?
nuclear pores that mediate transport of molecules between the nucleus and the cytoplasm.
what is the nuclear lamina?
a network of intermediate protein filaments that supports the inner
membrane.
what is the nuclear lamina composed of?
nuclear lamins and lamin-associated proteins.
what happens to lamina during mitosis and after mitosis ends?
they disassemble and then reassemble
what is the nuclear lamina essential for?
many nuclear activities such as DNA replication, transcription, and gene regulation
how are nuclear pores formed?
by the merging of the inner and outer nuclear membranes.
what do nuclear pores contain?
a nuclear pore complex (NPC), a cylinder-like structure that mediates bidirectional transport
what does the NPC contain?
nucleoporins
what is the nuclearplasm?
Nuclear content other than the chromatin and nucleolus.
what does the nuclearplasm contain?
proteins and other metabolites involved in the synthetic and metabolic activity of the chromatin and nucleolus.
what are somatic cells classified based on?
mitotic activity
what are the different mitotic activities in which somatic cells classified based on?
- static cell populations
- stable cell populations
- renewing cell population
what does static cell populations mean?
means they do not divide
nerve cells, cardiac muscle cells
what does Stable cell populations mean?
means they divide slowly
smooth muscle cells, periosteal and perichondrial cells, endothelial cells, fibroblasts
what does Renewing cell populations mean?
means they display regular mitotic activity
blood cells
what are the two categories of renewing cell populations?
- Slowly renewing populations:
1. smooth muscle cells of most hollow organs
2. fibroblasts of the uterine wall
3. epithelial cells of the lens of the eye - Rapidly renewing populations:
1. blood cells
2. epithelial cells
3. dermal fibroblasts of the skin
4. the epithelial cells and subepithelial fibroblasts of the mucosal lining of the alimentary tract
what is the cell cycle?
a self-regulated sequence of events controlling cell growth and division
the cell cycle includes:
interphase (G1, S, G2) and M phase (mitosis)
what is G1 phase?
cell growth, gathering of nutrients, and RNA/protein synthesis. Includes the restriction checkpoint, and the G1 DNA-damage checkpoint. Longest phase.
what is S phase?
DNA replication; monitored by the S DNA-damage checkpoint.
what is G2 phase?
cell prepares for cell division; monitored by the G2 DNA-damage checkpoint and the unreplicated DNA checkpoint.
what is M phase?
includes mitosis and cytokinesis; monitored by the spindle-assembly and chromosome-segregation checkpoints.
what do checkpoints ensure?
that the cell cycle progresses correctly and prevent division when damage is present.
what is a mitotic catastrophe?
it is caused by malfunction of cell cycle checkpoints may lead to cell death (apoptosis) and tumor cell development.
what is the cell cycle driven by?
cyclin-Cdk complexes
what is mitosis?
A process of chromosome segregation,
nuclear division producing,
two identical daughter cells.
what are the two things that mitosis includes?
karyokinesis (division of the nucleus) and cytokinesis (division of the cell).
what are the phases of mitosis?
- prophase
- metaphase
- anaphase
- telophase
what is prophase?
chromosomes condense, nuclear envelope disassembles, mitotic spindle develops.
what is metaphase?
chromosomes align at the metaphase plate.
what is anaphase?
sister chromatids separate and move to opposite poles
what is telophase?
nuclear envelope reforms, cytoplasm divides.
what is meiosis?
Involves two sequential nuclear divisions producing gametes with half the number of chromosomes and half the DNA of somatic cells.
what is meiosis divided into?
meiosis I and meiosis II
what is Meiosis I?
a reductional division.
what are the stages in meiosis I?
- Prophase I: homologous chromosomes pair, synapsis and crossing-over occur. Subdivided into leptotene, zygotene, pachytene, diplotene, and diakinesis.
- Metaphase I: paired chromosomes align at the equatorial plate.
- Anaphase I: homologous chromosomes separate.
what is meiosis II?
an equatorial division, similar to mitosis.
where sister chromatids separate
what can an abnormality in any of these rates can cause? (2 things)
- disorders of cell accumulation
(hyperplasia, cancer, autoimmune diseases) - disorders of cell loss
(atrophy, degenerative diseases, AIDS, ischemic injury)
what are some of the cell accumulation disorders?
- cancer
- lupus erythematosus
- glomerulonephritis
- viral infections
where are some cell loss disorders?
- AIDS
- Alzheimer disease
- Parkinson disease
- aplastic anemia
- myocardial infarction (heart attack)
cell death can be either….
programmed or nonprogrammed.
what is non programed cell death (necrosis) caused by?
acute cell injury, resulting in cell swelling and lysis and often accompanied by intense inflammatory response
Programmed cell death is a regulated process that may be _________
apoptotic or nonapoptotic.
what is apoptosis?
aspase-dependent and characterized by cell shrinkage, membrane blebbing, and DNA fragmentation. It does NOT cause inflammation.
what may apoptosis be triggered by?
internal (mitochondrial) or external pathways
what is apoptosis regulated by?
the Bcl-2 family of proteins
what is anoikis?
apoptosis induced by lack of cell-to-extracellular matrix interactions.
Signals from the extracellular matrix are sensed by______ that form an integral part of anchoring _________ matrix junctions
- integrins
- cell-to-extracellular
In __________ cancer, cells develop mechanisms to survive the______ process, including changes in ________ receptor types, activation of ________ factors, _____ activation, and growth factor receptor signaling.
- metastatic
- anoikis
- integrin
- antiapoptotic
- oncogene
necrosis and apoptosis
necrosis
1. injury of cell membrane
2. swelling
3. membrane breakdown
4. disintegration and inflammation
apoptosis
1. DNA fragmentation
2. decrease of cell volume
3. membrane bleeding
4. formation of apoptotic bodies
what THE HELL is programmed nonapoptotic cell death?
it is caspase-independent and is often characterized by membrane rupture.
Apoptosis is characterized by controlled ________, which maintains cell membrane integrity; thus, the cell “_________” without spilling its contents and damaging its neighbors
- autodigestion
- dies with dignity
Examples of cell death
- autophagy
- enosis
- paraptosis
- mitoptosis
- proptosis
- NETosis
- necroptosis
