Lectures 21-22 Flashcards
M phase =
Mitosis and cytokinesis
The central problem for a cell in M phase is to accurately separate and distribute its
chromosomes.
What are sister chromatids?
The duplicated chromosomes
What ties the two sister chromatids together?
Cohesins
What is the microtubule-organizing center in an animal cell?
centrosome
What is the centrosome made of?
hundreds of_-tubulin rings
What does the centrosome contain a pair of?
centrioles
What are centrioles made of?
a cylindrical array of short microtubules
What are the five stages of mitosis?
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
What are the three types of microtubules in the miotic spindle?
aster, kinetochore, and interpolar
What is the miotic spindle?
a complex cytoskeletal machine that is
composed of microtubules to separate the replicated chromosomes.
What happens during metaphase?
chromosomes aligned at the _mitotic spindle equator__
(or mitotic interface, mitotic plate…)
What happens during anaphase?
separation of sister chromatids by shortening the kinetochore
microtubules and move apart of the centrosomes
What happens during telophase?
a. daughter chromosomes arrive at the poles
b. reassemble of nuclear envelope via de-phosphorylation of __lamins__
c. assembly of __contractile ring__ for cytokinesis
What is cytokinesis?
A different cytoskeletal structure is responsible for cytokenesis called
contractile ring which consists of __myosin_ and __actin__ filaments.
What is the structure of microtubules?
- __tubulin hetero-dimers 13 protofilaments hollow tube
- polarity : -tubulin is the _+__ end growing faster; the two ends are
chemically different and behave differently
What are the major functions of microtubules?
- Anchoring membrane-enclosed organelles
- Guiding intracellular __transport__
a. Mediated by motor proteins
Two major motor proteins for microtubules
__kinesin__ & __dynein__ containing globular heads
b. Conduct __directional___ movement
Kinesins move towards the __plus__ end; dyneins to the __minus__ end - Cell division (both mitosis and meiosis)
- movement of cilia and flagella
What are the major functions of actin filament?
- Special cell structure: microvilli
- Cell shape: contractile bundles
- Cell migration: lamellipodium & filopodium
- Cell division: contractile ring
- Intracellular transport
- _muscle contraction__
What is a lamellipodium?
a sheet-like structure at the leading edge of crawling
cells.
What is filopodium?
a thread-like structure at the leading edge of crawling cells
What are the intracellular changes of cell migration?
a. protrusion –forming filopodia and lamellipodia
b. focal adhesion – using integrins proteins
c. attachment and traction
d. contraction at the back
What is muscle contraction called?
a sacromere
What are sarcomeres made of?
made up with __myosin__ filaments (thick filament) and
__actin_ filament (thin filament).
What mediates muscle contraction?
by Ca ions
What are drugs that interfere with microtubules used to treat?
cancer
What does the drug Taxol do?
stabilizes microtubules
What does the drug Vinblastine do?
binds to subunits and prevents polymerization.
What are homologous chromosomes?
Parental chromosomes which are similar but not identical
What are sister chromatids?
the twin copies of each replicated chromosome
What are daughter chromosomes?
separated sister chromatids
What is a synapsis?
homologous chromosomes pair along their length.
What is homologous recombination?
genetic exchange between homologous
chromosomes.
What is reduction division?
two successive divisions
What happens during the meiotic division I?
- Pairing of homologous chromosomes
- Homologous chromosomes cross over to form structures called
__chiasma__ (pl. __chiasmata___) - Genetic recombination occurs
- Separate __homologous__ chromosomes
- Sister chromatids are no longer identical due to __crossing over__.
What happens during the meiotic division II?
separate sister chromatids
What are the genetic variations during meiosis?
- crossovers during meiotic prophase I stage
- independent assortment of maternal and paternal homologues during
metaphase I & anaphase I stages - fertilization
What is a nondisjunction?
mproper separation of DNA during meiosis
What is aneuploidy?
causing abnormal number of chromosomes in cells
What is the cause of down syndrome?
trisomy 21
