Mitosis And Meosis

Front 1

Cyclin-Dependent-Kinases

Back 1

Require cyclins for activity. Regulate progression through different stages of the cell cycle.

Front 2

Cyclin

Back 2

Required for the function of cyclin dependent kinases to regulate the progression through the cell cycle.

Front 3

Cdk1

Back 3

Binds to cyclin A and triggers G2 to M transition.

Front 4

Cdk2

Back 4

Binds to Cyclins A or E and triggers cells from G1 to S phase.

Front 5

Cdk-4/Cdk-6

Back 5

Restriction point regulation

Front 6

Anaphase-promoting complex

Back 6

Inactivates and degrades cyclins by a ubiquitin-mediated proteolysis pathway.

Front 7

Centrosome duplication

Back 7

Necessary for the bi-polar spindle. Starts in G1 and goes to S phase and is completed in G2. Loss of regulation results in centrosome amplification which leads to apoptosis or cancer.

Front 8

Cytoskeleton dynamics

Back 8

Cytoplasmic microtubules disassemble and mitotic spindle microtubules assemble from the centrosomes.

Front 9

Prophase

Back 9

1. Condensin enters the nucleus
2. Chromosome condensation begins
3. Duplicated centrosomes begin to separate
4. Cell begins to round up
5. Intracellular membranes begin to disassemble
6. Cell surface markers internalized

Front 10

Condensin

Back 10

Proteins that initiate chromosome condensation.

Front 11

Prometaphase

Back 11

1. Nuclear envelope disassembles
2. Microtubules grow and shrink in asters
3. Kinetochores capture plus ends of microtubules
4. Chromosomes slide poleward along a microtubule
5. Chromosomes attach to both poles and congress to middle of spindle

Front 12

Metaphase

Back 12

1. Chromosomes align at the middle of spindle
2. Kinetochore microtubules extend from poles (minus ends) to sister kinetochores where they attach (positive end), motors (dynein) push chromosomes toward negative end of microtubules (poleward)
3. Interpolar microtubules extend from spindle poles and overlap at cell equator. Two motors plus end directed and minus end directed kinesin produce balanced forces to hold poles apart

Front 13

Metaphase plate

Back 13

The name of the chromosomes when they are aligned at the center of the cell.

Front 14

Role of cytoplasmic dynein in mitosis

Back 14

Moves the chromosomes towards the negative ends of the microtubules which are attached at the centrosomes.

Front 15

Role of kinesin in mitosis

Back 15

Moves the interpolar microtubules apart from each other to stretch the cell. Includes both plus end and minus end directed kinesins.

Front 16

Spindle Assembly Checkpoint

Back 16

1. Signaling by unattached kinetochores stops the cell from entering anaphase
2. Microtubule motor (CENP-E) at the kinetochores functions as a tension sensor
3. Status of kinetochore microtubule binding and tension is signaled by CENP-E to a kinetochore associated kinase BubR1 which activates Mad1 that signals Mad2 that blocs APC/C
4. The attachment of microtubules and proper tension results in inactivating BubR1, activating APC initiating anaphase APC/c which is like a trigger that when activates initiates anaphase chromosome movement

Front 17

Microtubule motor (CENP-E)

Back 17

Checks the tension between microtubules and kinetochores and if it is not equal it signals BubR1 to prevent continuation into anaphase.

Front 18

BubR1

Back 18

A kinetochore associated kinase that phosphorylates Mad1 preventing continuation into anaphase.

Front 19

Mad1

Back 19

Signaling molecule that signals Mad2 to block APC/C and prevent continuation into anaphase.

Front 20

Mad2

Back 20

Directly blocks action of APC/C preventing continuation into anaphase.

Front 21

Anaphase

Back 21

1. Cohesin is degraded
2. Sister chromatids separate
3. Chromatids approach poles (anaphase A)
4. Spindle poles migrate apart (anaphase B)

Front 22

Cohesin

Back 22

Proteins that hold sister chromatids together.

Front 23

Telophase

Back 23

1. Nuclear envelope reassembles around chromosomes
2. Cleavage plane is specified
3. Central spindle pushes poles apart

Front 24

Cytokinesis

Back 24

1. Early cytokinesis:
a. Acto-myosin ring contracts
b. Midbody forms
c. New membrane is inserted
2. Late cytokinesis:
a. Midbody forms
b. Chromatin decondenses and nuclear substructures reform
c. Cytoplasmic microtubules reform

Front 25

Aneuploidy

Back 25

Condition where one or more chromosomes are lost or gained within a diploid complement of chromosomes due to errors in mitosis.

Front 26

Consequences of mutation or disregulated checkpoints

Back 26

1. Kinetochore dysfunction and non-disjunction of chromatids
2. Multipolar spindle due to errors in regulating spindle poles (centrosome amplification)
3. Failure of cytokinesis resulting in tetraploidy
4. Other genomic instabilities such as breaks, translocations, deletions within the chromosome complement.

Front 27

Differences between meiosis and mitosis

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1. Meiosis has two cell divisions
2. Products are haploid vs. diploid
3. Products of meiosis are genetically different vs. identical
4. Prophase is much longer in meoisis
5. Genetic recombination occurs in meiosis
6. Kinetochore behavior is different in meiosis
7. Chromatid cohesion is different in meiosis

Front 28

When does meiosis occur in males?

Back 28

Human males produce 100 million sperm/day in testis via spermatogenesis after puberty.

Front 29

When does meiosis occur in females?

Back 29

Eggs are produced in follicles of ovary - 1 million primordial follicles with an oocyte arrested in diplotene stage of meiosis I. Following puberty, a small number of oocytes are activated and grow and are ovulated each month through reproductive life.

Front 30

Where does meiosis occur in males?

Back 30

Seminiferous tubules of testis

Front 31

Where does meiosis occur in females?

Back 31

Ovarian follicles.

Front 32

Purpose of meiosis

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Assures genetic recombination in concert with random reassortment of chromosomes. Re-shuffling of chromosomes produces genetic diversity.

Front 33

Pairing

Back 33

Alignment of homologous chromosomes within the nucleus

Front 34

Synapsis

Back 34

Process where by homologous chromosomes actually become intimately connected via a special scaffold-like structure called the synaptonemal complex enabling crossing over of DNA strands.

Front 35

Recombination

Back 35

Physical exchange of DNA between homologous chromosomes. Starts when pairing begins and when completed forms a chiasmata where recombination occurred.

Front 36

Chiasmata

Back 36

Specialized structure where crossing over and recombination has occurred.

Front 37

Prophase I

Back 37

The longest phase of meiosis that can last from days to years and is broken down into many stages.

Front 38

Leptotene stage

Back 38

Early stage where homologous chromosomes associate at their ends - telomeres.

Front 39

Bouquet stage

Back 39

Telomeres of all homologs come together at a site on the nuclear membrane.

Front 40

Zygotene stage

Back 40

Homologs undergo synapsis.

Front 41

Pachytene stage

Back 41

Synapsis is complete and synaptonemal complex is complete.

Front 42

Diplotene stage

Back 42

Synaptonemal complex disassembles and chromosomes condense further.

Front 43

Diakinesis

Back 43

Homologs become oriented to one of two poles of the spindle.

Front 44

Metaphase I

Back 44

Bivalents arranged at metaphase plate. Disjunction of homologous pairs occurs as bivalents are pulled apart.