cell division

new cells arives through the division of preexisitng ones

meiosis --> gametes

mitosis --> somatic cells

cytokinesis

"movement"

-the divsion of the cytoplasm

when complete-2 new daughter cells

Asexual Reproduction

(stages)

mitosis followed by cytokinesis

Chromosome

consist of single, long DNA double helix which is wrapped around proteins in a highly organized manner

DNA....

-encodes cell's hereditary info/genetic material

gene

lenght of DNA that codes for a particular protein or RNA found in the cell

Pre-mitosis....

each chrom is replicated

each of the DNA copies in a replicated chromosome

-2 joined together along entire lenght as well as centromeme

Sister Chromatid

chromatids from the same chromosome

Interphase

-active time cell is either growing or preparing to divide or fulfilling its specialized function in a multicellular individual 

G1 + S + G2

What is incorporated into DNA as it is being synthesized?

phosphorus and thymidine

Synthesis (S) phase

-part of interphase

-replication of the genetic material is separated from the partitioning of chromosome copies during M phase

Cell Cycle

sequence of events that starts w/the formation of a eukaryotic cell, throught the duplication of its chroms, to the time it undergoes division itself

time lag

occurs btwn the end of S phase and the beginning of M phase

G2 phase

chrom replication is complete but mitosis hasnt begun yet

G1 phase

occurs after M phase but before S phase

Why are there gaps?

-besides copying their chroms during S phase, dividing cells also must replicate organelle and manufacture additional cytoplasm

-before mitosis can take place, the parent cell must grown large enough and synthesize enough organelles that its daughter cells will be normal in size and function

histones

Eukaryotic chroms consis of DNA associated w/ these gloubular proteins

chromatin

DNA protein material in eukaryotes

during interphase chromatin is....

"relaxed"/uncondensed

-long threadlike strands

Chromatin contains

-one lone DNA double helix and sister chromatids represent exact

IPPMAT

interphase is followed by mitotic subphases of prophase, prometaphase, metaphase, anaphase, and telophase

spindle apparatus

structure that produces mechanical forces taht

(1) pull chromosomes to the poles of the cell

(2) push the poles of the cell away from eachother

polar mictrotubules

(in spindle apparatus)

-extend from each spindle and overlap one anothe rin the middle of the cell

kinetochore microtubules

-attach to the chromosomes

centrosome

microtubule organizing center

-polar and kinetochore microtubules originate here

Kinetochore

-where the attachment btwn the kineotchore microtubules and each chromatid is made

-locate at the centromere region

-each chrom has 2 (one on each side)

centromere region

where sister chromatids attach most persistently to each other during mistosis

Metaphase Plate

imaginary plane where chroms line up when a metaphase ends

Interphase

-after chrom replication each chrom is composed of 2 sister chromatids

-centrosomes have replicated

PRophase

chroms condense

-spindle apparatus begins to form

Prometaphase

-nuclear envelope breaks down

-kinetochore microtubules contact chromosome at the kinetochore

Metaphase

chroms complete mrgration to the middle of the cell

(metaphase plate)

Anaphase

-sister chromatids separate

-chroms pulled to opposite pole

-kinetochore shorten

-motor proteins pull chromes to opp poles

-replicated chroms split to 2 identical sets of unreplicated

Telophase

nuclear envelope reforms

-spindle apparatus disintegrates

Cell division Begins (Cytokinesis)

actin myosin ring causes the plasma

mem to begin pinchin

Cytokinesis in plants

Cell Plate (plant cytokinesis)

structure where vesicles from golgi apparatus are transported of the middle of the dividing cell

Vesicles (plant cytokinesis)

carry components of cell wall and plasma membrane

(gradually build up completing the cell plate and dividing the 2 daughter cells)

cleavage furrow

forms due to a ring of actin filaments that formed

(myosin-motor protein binds to actin filament; mysoin binds to ATP/ADP part of protein moves causing actin filaments to slide--> cell pinches into 2)

Mitotic Spindle Forces

-spindle apparatus composed of microtubules

-microtubules composed of alpha and beta tubulin dimers

-the # of tublin dimers a microtubule has determines its lenght

-microtubules are asymmetric

difference in cell cycles due to....

variation in the lenght of the G1 phase

(rapid division essentially no G1 phase)

G0 phase

essentially stuck in G1

(cells after they mature-ex nerve)

Mitosis promoting factor (MPF)

induces mitosis in all eukaryotes

-contains protein kinase and a cylin

protein kinase

-enzyme that catalyzes the transfer of a phosphate group from ATP to a target protein 

-frequently acts as a regulatory elemtn in the cell

Cyclins

Cyclin dependent kinase (CdK)

protein kinase subunit of MPf

-catalyzes phosphorylation of other proteins to start Mitosis

MPF triggers...

the onset of the M phase

-the # of complete MPF dimmers builds up steadily during interphase

Destruction of MPF

-MPF triggers chain of events that lead to its own destruction

-negative feedback

negative feedback

-occurs when a process is slowed or shut down by one of its products

G1 checkpoint in order to pass...

-size-cell must reach a certain size so its daughter cell willb e large enought to function normally

-abailability of nutrients-if conditions are poor or not

-social signals- cells in multicellular organiss do(not) pass through in respons to signaling molecules from other cells

-Damage to DNA-if physically damage protein p53 activates gene that will eitehr stop cycle until damage is repaired or apoptosis

G2 Checkpoint will pass if....

chromosomes have successfully replicated

DNA is undamaged

-activated MPF is present

Metaphase checkpoitn will pass if...

all chromes are attached to spindle apparatuses

Cancer

-uncontrollable cell division

-arise from cells in which cell cycle checkpoints have failed

2 types of cancerous cell defects

(1) defects that make the protein required for cell growth to activate when they should be

(2) defects that prevent tumor suppressor genes from shutting down the cell

metastasis

-the processing of detaching and estabilishing secondary tumors elsewhere

-cells become malignant and cancerous if they gain ability to detatch from original tumor and invade other tissues

Social Control

-idividual cells should be allowed to divide only when their growth is in the best interest of the organism as a whole

(based on growth factors)

growth factors

polypeptides or small proteins that stimulate cell division

serem

liquid portion of blood that remains after blood cells and cell fragments have been removed