Cell Biology - 1.6 Cell Division Flashcards
Understandings:
- Mitosis is division of the nucleus into two genetically identical daughter nuclei
- Chromosomes condense by supercoiling during mitosis
- Interphase is a very active phase of the cell cycle with many processes occurring in the nucleus and cytoplasm
- Cytokinesis occurs after mitosis and is different in plant and animal cells
- Cyclins are involved in the control of the cell cycle
- Mutagens, oncogenes and metastasis are involved in the development of primary and secondary tumours
Interphase + process (DOCTOR)
Interphase is an active period in the cell cycle when many metabolic reations occur
(Many events need to occur in interphase to prepare the cell for successful division
These key processes include:
D - NA replication – DNA is copied during the S phase of interphase
O - rganelle duplication – Organelles must be duplicated for twin daughter cells
C - ell growth – Cytoplasmic volume must increase prior to division
T - ranscription / translation – Key proteins and enzymes must be synthesised
O - btain nutrients – Vital cellular materials must be present before division
R - espiration (cellular) – ATP production is needed to drive the division process
DNA Supercoiling - Chromatin versus Chromosome
Chromatin:
1) DNA is usually loosely packed within the nucleus as unravelled chromatin
2) In this unravelled form, the DNA is accessible to transcriptional machinery and so genetic information can be translated
3) DNA is organised as chromatin in all non-dividing cells and throughout the process of interphase
Chromosome:
1) DNA is temporarily packaged into a tightly wound and condensed chromosome prior to division (via supercoiling)
2) In this condensed form, the DNA is able to be easily segregated however is inaccessible to transcriptional machinery
3) DNA is organised as chromosomes during the process of mitosis (condense in prophase, decondense in telophase)
DNA Supercoiling - Chromosome versus Chromatid
A chromosome is the condensed form of DNA which is visible during mitosis (via microscopy)
- > As the DNA is replicated during the S phase of interphase, the chromosome will initially contain two identical DNA strands
These genetically identical strands are called sister CHROMATIDS and are held together by a central region called the centromere
-> When these chromatids separate during mitosis, they become independent chromosomes, each made of a single DNA strand
Mitosis = (very meh paragraph explanation taken from booklet)
“division of nucleus into 2 genetically identical daughter nuclei. Mitosis for growth, embryonic development and tissue repair which occurs in all cells and results in two ells, each with the same # of chromosomes. Cells in which rapid mitosis occours are in the growth tips of roots and shoots and in the developing embryo. Mitosis is also used in asexual reproduction”
Cell cycle (2 phases)
Cell cycle = series of events that take place in a cell leading to its division and duplication (replication) - it includes both mitosis (cell division) and cell growth (+ culminated in the division of a cell into 2 daughter cells)
(length of cycle = 8minutes - 24 hours)
1) interphase
2) M (mitotic) phase
Interphase - cell cycle
- stage in the development of a cell between 2 successive divisions
Sub stages:
1) G1 = first gap stage, cell grows and preps for DNA
2) S = synthesis stage + replication (DNA is replicated)
3) G2 = 2nd gap stage, cell finishes growing + preps for cell division
Interphase continued (BEFORE MITOSIS)
- DNA is present as uncondensed
- DNA is contained within chromatin and clearly defined nucleus
- centrosome/other organelles have been duplicated
- cell is enlarged in preparation for division
M (mitotic) phase - cell cycle
= the period of the cell cycle - cell and contents divisde to create 2 genetically identical daughter cells
Sub stages:
1) mitosis = nuclear division (DNA = separed into 2 identical nuclei)
2) cytokinesis = cytoplasmic division (=cellular contents = segregated and cell splits into 2)
Cyclins =
(refer to diagrams on bioninja!)
= Chemicals that undergo periods of chemical synthesis and breakdown as they interact with the cell cycle and the environment to signal the beffins and end of the different stages (eg. the interphase and the mitotic phase)
= a family of regulatory proteins that control the progression of the cell cycle
- activate CDKs (cyclin dependant kinases) (controls cell cycle progression via phosphorylation)
cyclin expression patterns:
- cyclin concentrations = tightly regulated to ensure the cell cycle progresses in a proper sequence
- Different cyclins specifically bind to and activate different classes of cyclin dependant kinases
- Cyclin levels = peak when their target protein is required to function and remain at lower levels at all other times
purpose of DNA replication in cell division:
= you need to have a full copy of DNA/genetic info for the daughter cells to 1) be created and 2) survive
Mitosis =
= process of nuclear division where DNA molecules are arranged into 2 separate nuclei (the division of the cell in 2 (cytokinesis) occours concurrently w/ final stage of mitosis) - parent cell devising into 2 or more daughter cells (cell division is usually a small segment of a larger cell cycle
Cell division occours in the following circumstances:
1) Development and growth = # of cells within an organism increases by mitosis (ie development of a multicellular body from a single celled zygote)
2) Cell replacement = in some parts of body - new cells are formed by mitosis and so are exact copies of the cells being replaced
3) Asexual reproduction = some organisms produce genetically similar offspring through asexual reproduction in bacteria and vegetative reproduction in plants
8 step process:
1) Interphase
2) early prophase
3) late prophase
4) metaphase
5) anaphase
6) late anaphase
7) telophase
8) cytokinesis
Interphase - mitosis (1)
- stage in the development of a cell between 2 successive divisions
Sub stages:
1) G1 = first gap stage, cell grows and preps for DNA
2) S = synthesis stage + replication (DNA is replicated)
3) G2 = 2nd gap stage, cell finishes growing + preps for cell division
Interphase continued (BEFORE MITOSIS)
- DNA is present as uncondensed
- DNA is contained within chromatin and clearly defined nucleus
- centrosome/other organelles have been duplicated
- cell is enlarged in preparation for division
early prophase - mitosis (2)
DNA continues condensing into chromosomes and the nuclear membrane beings to dissolve
- DNA supercoils and chromosomes condense
- chromosomes = comprised of genetically identical sister chromatids
- paired centrosomes move to the opposite poles of the cell + form microtubual spindle fibres
- nuclear membrane breakdown and the nucels dissolves
late prophase - mitosis (3)
chromosomes continue to coil up and appear as double-chromatids
centrosomes in plant cells lack centrioles. In animal cells, centrioles are associated with the centrosomes but their exact role in unclear
- DNA supercoils and chromosomes condense
- chromosomes = comprised of genetically identical sister chromatids
- paired centrosomes move to the opposite poles of the cell + form microtubual spindle fibres
- nuclear membrane breakdown and the nucels dissolves
Metaphase - mitosis (4)
The mitotic spindle is formed to organise the chromosomes. The spindle consists of fibres made of microtubules and proteins
- microtubal spindle fibres from both centrosomes connect to the centromere of each chromosome
- microtubal depolymerization causes spindle fibres to shorten in length and contract
-> causes chromosomes to align along the centre of the cell
