Lectures 21-22

Question 1

M phase =

Answer 1

Mitosis and cytokinesis
The central problem for a cell in M phase is to accurately separate and distribute its
chromosomes.

Question 2

What are sister chromatids?

Answer 2

The duplicated chromosomes

Question 3

What ties the two sister chromatids together?

Answer 3

Cohesins

Question 4

What is the microtubule-organizing center in an animal cell?

Answer 4

centrosome

Question 5

What is the centrosome made of?

Answer 5

hundreds of_-tubulin rings

Question 6

What does the centrosome contain a pair of?

Answer 6

centrioles

Question 7

What are centrioles made of?

Answer 7

a cylindrical array of short microtubules

Question 8

What are the five stages of mitosis?

Answer 8

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

Question 9

What are the three types of microtubules in the miotic spindle?

Answer 9

aster, kinetochore, and interpolar

Question 10

What is the miotic spindle?

Answer 10

a complex cytoskeletal machine that is
composed of microtubules to separate the replicated chromosomes.

Question 11

What happens during metaphase?

Answer 11

chromosomes aligned at the _mitotic spindle equator__
(or mitotic interface, mitotic plate…)

Question 12

What happens during anaphase?

Answer 12

separation of sister chromatids by shortening the kinetochore
microtubules and move apart of the centrosomes

Question 13

What happens during telophase?

Answer 13

a. daughter chromosomes arrive at the poles
b. reassemble of nuclear envelope via de-phosphorylation of __lamins__
c. assembly of __contractile ring__ for cytokinesis

Question 14

What is cytokinesis?

Answer 14

A different cytoskeletal structure is responsible for cytokenesis called
contractile ring which consists of __myosin_ and __actin__ filaments.

Question 15

What is the structure of microtubules?

Answer 15

1. __tubulin hetero-dimers  13 protofilaments  hollow tube
2. polarity : -tubulin is the _+__ end growing faster; the two ends are
   chemically different and behave differently

Question 16

What are the major functions of microtubules?

Answer 16

1. Anchoring membrane-enclosed organelles
2. 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
3. Cell division (both mitosis and meiosis)
4. movement of cilia and flagella

Question 17

What are the major functions of actin filament?

Answer 17

1. Special cell structure: microvilli
2. Cell shape: contractile bundles
3. Cell migration: lamellipodium & filopodium
4. Cell division: contractile ring
5. Intracellular transport
6. _muscle contraction__

Question 18

What is a lamellipodium?

Answer 18

a sheet-like structure at the leading edge of crawling
cells.

Question 19

What is filopodium?

Answer 19

a thread-like structure at the leading edge of crawling cells

Question 20

What are the intracellular changes of cell migration?

Answer 20

a. protrusion –forming filopodia and lamellipodia
b. focal adhesion – using integrins proteins
c. attachment and traction
d. contraction at the back

Question 21

What is muscle contraction called?

Answer 21

a sacromere

Question 22

What are sarcomeres made of?

Answer 22

made up with __myosin__ filaments (thick filament) and
__actin_ filament (thin filament).

Question 23

What mediates muscle contraction?

Answer 23

by Ca ions

Question 24

What are drugs that interfere with microtubules used to treat?

Answer 24

cancer

Question 25

What does the drug Taxol do?

Answer 25

stabilizes microtubules

Question 26

What does the drug Vinblastine do?

Answer 26

binds to subunits and prevents polymerization.

Question 27

What are homologous chromosomes?

Answer 27

Parental chromosomes which are similar but not identical

Question 28

What are sister chromatids?

Answer 28

the twin copies of each replicated chromosome

Question 29

What are daughter chromosomes?

Answer 29

separated sister chromatids

Question 30

What is a synapsis?

Answer 30

homologous chromosomes pair along their length.

Question 31

What is homologous recombination?

Answer 31

genetic exchange between homologous
chromosomes.

Question 32

What is reduction division?

Answer 32

two successive divisions

Question 33

What happens during the meiotic division I?

Answer 33

• 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__.

Question 34

What happens during the meiotic division II?

Answer 34

separate sister chromatids

Question 35

What are the genetic variations during meiosis?

Answer 35

1. crossovers during meiotic prophase I stage
2. independent assortment of maternal and paternal homologues during
   metaphase I & anaphase I stages
3. fertilization

Question 36

What is a nondisjunction?

Answer 36

mproper separation of DNA during meiosis

Question 37

What is aneuploidy?

Answer 37

causing abnormal number of chromosomes in cells

Question 38

What is the cause of down syndrome?

Answer 38

trisomy 21