1.6 CELL DIVISION Flashcards
prokaryotic cells divide by?
Binary Fission
eukaryotic cells divide by?
Mitosis
Mitosis is needed for
Growth
Assexual reproduction
Tissue repair
Embryonic development
Cell Cycle
the series of events through which cells pass to divide and create two identical daughter cells
Interphase
DNa replication
Organelle duplication → for twin daughter cells
Cell growth → cytoplasmic volumen must increase
Transcription/translation
Obtain nutrients →vital cellular materials must be present
Respiration → ATP production is needed
G1
Increase the volume of cytoplasm
Rapid protein synthesis to allow cell growth
Organelles produced
S
DNA replication takes place
G2
Increase the volume of cytoplasm
Protein synthesis to produce proteins needed for cell division
Organelles produced
Prophase
DNA supercoils → chromatins condense
Nucelar membrane desitegrates
Spindle fibres start to form
Centrioles move to opposite poles
Metaphase
Spindle fibres bind to centromere
Sister chromatids are aligned at the equatorial plate
Anaphase
sister chromatids are separated
Telophase
Nuclear membrane start to reform at each pole
Spindle fibres disintegrate
Cell elongates in preparation of cytokinesis
Cytokinesis in animal cells
Cytokinesis in plant cells
Mitotic index
a measure of the proliferation status of a cell population
MI = cells in mitosis / total number of cells
Cell Cyclins
a family of proteins that control the progression of cells through the cell cycle
G1 phase
Cyclin D levels gradually increase
assembles proteins for DNA replication
S phase
Cyclin E activates DNA replication
G2 phase
Cyclin S promotes progression through the cycle
Mitosis
Cyclin B initiates mitosis
Tumorigenesis
the formation of a tumor
Tumour
mass of cells that divide uncontrollably
Malignant tumours
cancerous growth that is often resistant to treatment
It may spread to other parts of the body
Benign tumour
usually localised and does not spread to other partos of the body
respond well to treatment
metastasis
when a primary tumor detaches form its original location and moves into another
primary tumor → secondary tumour
Mutagens
agents that cause gene mutations
potentially causes cancer
examples of mutagens
high energy radiation
short-wave ultraviolet light
some viruses
chemicals taht cause mutations (carcinongens)
Mutation in a oncogene
causes a malfunction in the control of the cell cycle → uncontrolled cell division → tumour formation
oncogene
a gene which in certain circumstances can transform a cell into a tumor cell.
