Biology - chapter 4

Stages of binary fission

DNA replication, elongation, septum formation, cell division

DNA replication

circular chromosome is uncoiled and the DNA is replicated, Plasmids also replicate

Elongation

the cell elongates to prepare for cell separation, the duplicated circular chromosomes migrate to opposite ends

Septum formation

plasma membrane begins to pinch inward and creating a septum, plasmids won’t always be evenly distributed between the two new cells

Cell division

new cell wall and membrane are formed down the centre of the cell

Purposes of cell replication

growth and development, maintenance and repair, reproduction

3 main stages of eukaryotic cell cycle

interphase, mitosis, cytokinesis

G1

increases cytosol volume, synthesises proteins for DNA replication, duplication of organelles

S stage

cell replicates its DNA turning one chromosome into two genetically identical sister chromatids which are held together by a centromere

G2

increasing the cytosol volume, synthesising proteins in preparation for mitosis

stages of apoptosis

activation of caspases, digestion of cell contents, cell shrinks, membrane blebbing and breakage

Activation of caspases

activated by either the mitochondrial or death receptor pathway

Digestion of cell contents

caspases cleave intracellular proteins, which leads to the breakdown of organelles

Cell shrinks

the cell and nucleus shrink as intracellular material is broken down

Membrane blebbing and breakage

organelles and cytoskeleton are digested, weakening structural integrity of the cell, apoptotic bodies detach from the cell

Prophase

nuclear membrane and nucleolus disappear, chromosomes condense, centrioles go to the opposite poles of the cell and begin creating spindle fibers

Metaphase

spindle fibers fully form and attach to the centromere of each chromosome, guides chromosomes to the middle of the cell where it lines up

Anaphase

spindle fibres contract, splitting the centromere and pulling sister chromatids to opposite ends of the cell.

Telophase

chromosomes densely pack together at opposite ends of cell, new nuclei form, spindle fibers disintegrate, chromosomes decondense

Characteristics of cancer cells

Self sufficiency, antigrowth deactivation, increased survival, blood supply formation, tissue invasion and metastasis