Mitosis Flashcards
Why do Multicellular Eukaryotes depend on cell division?
Development from a fertilized cell
Growth
Repair
Results in daughter cells with identical genetic information (DNA)
All the DNA in a cell constitutes the cells ___
Genome
What can a genome consist of?
It can consist of a single DNA molecule (prokaryotic cells) or a number of DNA molecules (eukaryotic cells)
DNA molecules in a cell are packaged into ____
chromosomes
Eukaryotic chromosomes consist of what?
Chromatin
What is Chromatin?
A complex of DNA & Protein (Nucleosomes) that condense during cell division
What are Somatic Cells?
Non-Reproductive Cells
How many sets of chromosomes do Somatic Cells have?
They have two sets
What are Gametes?
Reproductive Cells: Sperm and Eggs
How many chromosomes are in Gametes?
Have half as many chromosomes as somatic cells
What is a Karyotype?
An image that reveals an orderly arrangement of chromosomes
What are Homologous Chromosomes?
Matching pairs of chromosomes that can possess different versions of the same gene
What happens in preparation for cell division in Eukaryotic Cell Division?
DNA is replicated and the chromosomes condense
In Eukaryotic Cell Divison, each duplicated chromosome has what?
Two sister chromatids (joined copies of the original chromosome)
Each set of sister chromatids attached along their lengths by?
Cohesins
What is a centromere?
It is the narrow “waist” of the duplicated chromosome where the two chromatids are most closely attached
The cell cycle consists of what two phases?
Mitotic (M) Phase (Mitosis and Cytokinesis)
Interphase
What is Interphase?
Interphase accounts for 90% of the cell cycle and can be divided into sub-phases.
What are the sub-phases of Interphase
G1 Phase ("First Gap")
S Phase ("Synthesis")
G2 Phase ("Second Gap")Packing Ratio for Linear DNA
1
Packing Ratio for Nucleosome
6X
Packing Ratio for Nucleosome around 30 nm Fiber
1000x
Packing Ratio for Mitotic Chromosome
10,000X
G2 of Interphase Info
Chromosomes are duplicated, uncondensed
Centrosomes appear with Centriole pairs
Prophase information
Two sister chromatids of one chromosome appear
Early Mitotic Spindle with Asters separating
Prometaphase Information
Fragments of Nuclear Envelope disappear
Nonkinetochore Microtubules start to expand
Metaphase Information
The Centrosomes are each at one spindle pole.
Everything lines up on the Metaphase Plate
Anaphase Information
Daughter Chromosomes start to disappear from one another and separate
Telophase and Cytokinesis Information
Cleavage Furrow forms, with Nucleolus forming with Nuclear Envelope forming.
What is the Mitotic Spindle made of?
It is a structure made of microtubules that control chromosome movement during mitosis
Where does the assembly of spindle microtubule begin?
In the centrosome
The microtubule organizing center (MTOC) includes..
Basal bodies associated with cilia and centrosomes
When the centrosome replicates during interphase.. what happens?
It forms two centrioles that migrate to opposite ends of the cell during prophase and pro-metaphase
During prometaphase, some spindle microtubules attach to..
kinetochores of chromosomes (kinetochore fibers) and begin to move the chromosomes
Are Non-kinetochore microtubules connected to centromeres?
No
What are Kinetochores?
Protein complexes associated with centromeres
At metaphase the chromosomes…
Are all lined up at the metaphase plate, a plane midway between the spindle’s two poles
Non-Kinetochore Microtubules from opposite poles ..
overlap and push against each other, elongating the cells
In Telophase, genetically..
identical daughter nuclei form at opposite ends of the cell
Cytokinesis begins during..
Anaphase or telophase and the spindle eventually disassembles
Eukaryotic Cell Cycle is regulated by a Molecular Control System which..
Controls frequency of cell division varies with the type of cell
Differences result from regulation at the molecular level
Cancer cells manage to escape the usual controls on the cycle
The sequential events of the cell cycle are directed by a distinct
Cell cycle control system, which is similar to a clock.
Cell Cycle Control System regulaed by both
Internal (Cylin + Cyclin Dependent Kinases (Cdks)
And External Controls (Growth Factors)
With change in concentration of its cyclin partner, the activity of a Cdk
Rises and falls
The clock has specific ..
checkpoints where the cell cycle stops until a go-ahead signal is received
Which checkpoint is the most important for most cells?
G1
What happens if a cell receives a go-ahead signal at the G1 checkpoint?
It will usall complete the S, G2, and M phases and Divide
What happens if a cell does not receive the go-ahead signal?
It will exit the cycle, switching into a non-dividing state called the G0 phase (quiescent heart muscle cells and nerve cells)
What does MPF stand for?
Maturation-Promoting Factor
What is MPF?
A cyclin-CDK complex
What does the MPF do?
Triggers cell’s [assage past the G2 checkpoint into the M phase
Phosphorylates proteins during cell division
Promotes spindle formation
Promotes condenation of chromosomes
Contributes to degradation of nuclear envelop, ER, and Golgi
Anchorage Dependence?
Cells require a surface for division
Density-Dependent Inhibition
Cells form a single layer
Density-Dependent inhibition also
have cells that divide to fill a gap and then stop
A normal cell is converted to a cancerous cell by a process called
Transformation
If abnormal cells remain only at the original site, the lump is caleld a
Benign Tumor
If abnormal cells move away from the initial site to other parts of the body
Metatasis
Cancer cells do not respond normally to..
The body’s control mechanisms
Cancer cells need growth factors to grow and divide. However,
They made their own growth factors
They may convey a growrth factors signal w/o the presence of a growth factor
They may have an abormal cell cycle control system
