mitosis/asexual Flashcards
(26 cards)
asexual reproduction
offspring are produced by a single parent without the participation of sperm and egg cells
offspring are genetic copies of the parent and of each other
binary fission
equal division
budding
an unequal distribution of cytoplasm
regeneration
the ability of an organism to regrow lost body parts by mitosis
cell cycle : interphase
chromosomes duplicate and cell parts are made and the cell grows
cell cycle : mitotic phase
duplicated chromosomes are evenly distributed into 2 daughter nuclei
interphase
Individual chromosomes contain very long DNA molecule associated with proteins and are visible only when the cell is in the process of dividing
Chromosomes occur in the form of thin loosely packed chromatin fibers
Before a cell starts dividing, the chromosomes produce sister chromatids join together at the centromere
S-phase : DNA replication
Nucleic acids (DNA & RNA) are a class of organic macromolecules which are made of subunits called nucleotides
DNA & RNA - blueprints for proteins & control the life of a cell
DNA molecules are organized into structures called chromosomes
Nucleotides form a series of units called genes
Genes
Nucleotides are composed of a sugar, phosphate & nitrogenous bases
Nitrogenous bases
Purines :
Adenine - A
Guanine - G
Pyrimidines :
Thymine - T
Cytosine - C
DNA consists of 2 polynucleotides twisted around each other in a double helix
Base Pair Rule
A : T - 2 bonds
C : G - 3 bonds
1st step : Replication
Unwind and unzip DNA
Helicase enzyme unwinds part of DNA helix by breaking the hydrogen bonds that link the complementary bases
2nd step : Replication
Build daughter DNA strand
Accomplished by enzymes called DNA polymerase that add new complementary bases
DNA Polymerase
The original strands that are being copied that are called templates
DNA polymerase acts as a proofreader
An mutation in DNA may occur once per 1000 nucleotides
Mitosis
Cell division involves the seperation of sister chromatids and results in 2 daughter cells, each containing a complete and identical set of chromosomes
Stages of mitosis ( cell division )
Prophase
Chromatin coils and shortens becoming visible double stranded chromosomes
Centrioles move towards the poles of the cell
The mitotic spindle forms a microtubule structure that helps separate chromosomes during mitosis
The nuclear membrane begins to break down
Stages of mitosis ( cell division )
Metaphase
Chromosomes lineup in the middle of the cell at the metaphase plate
Microtubules are attached to sister chromatids at the kinetochore
Stages of mitosis ( cell division )
Anaphase
Sister chromatids separate and are pulled by the mitotic spindle to opposite poles
Stages of mitosis ( cell division )
Telophase
One complete set of chromosomes gather at each pole
The mitotic spindle breaks down
A nuclear membrane forms around each set of chromosomes
Chromosomes uncoil and elongate, becoming chromatin again
Cytokinesis (cytoplasm division)
In animals: cytokinesis occurs by a constriction of the cell (cleavage)
In plants : a membranous cell plate splits the cell in 2
Growth factors
Signals affecting critical checkpoints in the cell cycle determine whether a cell will go through the complete cycle and divide
The binding of growth factors to specific receptors on the plasma membrane
Cancer
Cancer cells produce malignant tumors
Cell cycle checkpoints fail
Divide excessively to form masses called tumors
Do not respond to limits of anchorage, density or growth factors
Radiation and chemotherapy are effective cancer treatments because they interfere with cell division
Mitotic cell division functions in :
Growth
Replacing damaged cells
Asexual reproduction
Plant growth
Meristem - regions of actively dividing undifferentiated cells (growth tissue, meristemstic tissue)
Vertical growth meristems in the stem and roots
Horizontal growth bands of metistematic tissue in the stem
Stem Cells
Undifferentiated cells that renew themselves by mitosis
Have the ability to be transformed into any type of cell
Equivalent of meristem cells in plants
