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Genetics - Coggle Diagram
Genetics
Meiosis:
Prophase 1: The chromosomes condense and the nuclear membrane breaks down releasing the chromosomes into the cytoplasm. Centriols move towards the poles and spindle fibers form. Note that the chromosomes also cross over through the process of synapsis to create variation in this step
Synapsis: Is the exchange of genetic information between sister chromatids. This increases the variation and is one of hte reaons why siblings can never by identical (excluding identical twins ofcourse)
Metaphase 1: The spindle fibers direct the homologous pair to line up in a "plate in the center of the cell. The spindle fibers then attachtot the centromeres getting ready to divide the homologous paris.
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Independent assortment: Image the cell having a north and south pole and the equatoriol plate of homologous paired chromosomes make up the equator. One of the chromosomes from each homologous pair is on the north side and the other on the south side. Independent assortment is the facts that the chromosomes from the homologous pair can be on either side of the equator and are will randomly end up on one side. This creates more variation becusase there are millions of possible combination as to which homologous pair will end up in one of the two cells.
Anaphase 1: The spindle fibers pull the homologous pairs apart and pull the towards the centriols (poles). At this point two cells will form each with 23 chromosomes (23n)
Telophase 1: The chromosomes unwind forming chromatin and the nuclear membrane reforms. Ussually telophase 1 doesn't occur and the cycel goes straight to prophase 2. This is becuase it is extra energy to unwind the chromosomes and reform the nuclear membrane when the oppoite will happen in prophase 1.
Prophase 2: If telophase 1 doesn't occur (most of the time), the centriols move to the poles and spindle fibers form.
Metaphase 2: The spindle fibers direct the chromosomes to the centre of the cell creating the equtorial plate and attach the the centromeres.
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Telophase 2: The chromatids (considered chromosomes even on there own) unwind to form chromatin and the nuclear membrane reforms. By the end of telophase 2, 4 cell have been created each with 23 chromosomes.
Reproductive Stratagies:
Spore: Spores divide mitotically to produce gametophytes. Note that the gametophytes are all haploid and genetically identicle.
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Gametes: Form when gametes fertalize each other and produce diploid zygotes. The zygotes divide mitotically and produce sporophytes.
A sexual Reproduction: When a species is able to reproduce with itself. This means that the new species will have no variation (all genetically identicle), leaving them suseptable to being whipped out. However, a sexual species are also able to reproduce in mass and very quickly.
Parthenogenisis: A form of a sexual reproduction where unfertalized eggs devlope into adults. The adult can be either diploid or haploid.
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Mitosis:
Prophase: The chromosomes are in hte form of chomatin which is the long stringy strand similar to pasta noodles. This is tightly package to from the commonly known chromosome shapes. The nuclear membrane also breaks down releasing the chromosomes into the cytoplasm. Centrioles also form and move to the poles of the cell and begin forming spindle fibers.
Metaphase: Spindle fibers attach to the centromeres of the chromsomes and guide them to the centre of the cell creating the cell plate. The cell is now ready to begin dividing the chromsomes
Anaphase: The spindle fibers seperate the sister chromatids from each other and pull them to opposite poles.
Telophase: Once the chromatids reach the poles, the spindle fibers begin to break down and the nuclear membrane begins to reform. The chromatids begin to unwind and form the longer DNA strands called chromatin. Remember after interphase, the 46 chrmatides areduplicated to form 92 chromatids. These are in pairs (sister chromatids) so they are still considered only 46 chromosomes. Once the cell divides, the two cell then have 46 identicle chromatids which by themselves are also considered chromosomes.
Interphase: In this stage, all the choromosomes are in the form of chromatids. These chromatids duplicated and form sister chromatides.
Nondisjunction:
mieotic non-disjunction: Is the unequal division of chromosomes into dauter cells. This can lead to non-fertile gametes or gametes that will result in a bavby with a disorder being born (down syndrom
Monosomy: Is when there is a missing chromosome. E.g. turner syndrome (female with only 1 X chromosme) They are infertile.
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Secondary mieotic nondisjunction: When an indvidual arises from meiotic non-disjunction (individual with missing or extra chromosome) produces nondisjunction gametes. They can also have a child with a non-disjunction disorder but are more likly to have non-fertile gamets. It is also possible for them to have a normal child.
Mitotic Non-disjunction: Occurs during embryotic development and is when some cells in the body may have a different number of chromsomes than other parts.
Cloning: You can take an egg from a donar female, remove it's nucleus, take cells from organism desired to be cloned, re-plant the egg into the donar organism and they will give birth to an organsim genetically identical to the one whos cell was taken.
Pluripotent: When some differentiation has occured but the cell is able to give rise to several types of cells (almost if not all types of cells). They can't give rise to an entirely new organism though.
Stem cells: Can specialize/differntiate into mutliple differnet cell types. they are found in the bone marrow and and divide an infinit number of times unlike other cells. Stem cells act as a resovior to repair or replace damaged cells. Recently a procedure was developed which added 4 new gene types to the blastula cells (recombinant DNA tech using restriction enzymes and ligase to add the DNA fragements). This de-differnetiated cells could then be used to grow into any tissue or boy structure potentially repairing damaged organs and more.
Multipotent: Are cells that are slightly more differnetiated than plruipotent cells and can give rise to several types of cells, but not all types of cells. An eample of multiponent cells are stem cells found in bone marrow.
Totipotent: When a cell is able to give rise to a completely new identicle oranism. This can be plant stems, roots, or even cells form the blastula where a cell is taken from the cell mass and it can grow completely indipendently (same as how identicle twins are born).
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Clining, differnetiation and Stem Cellls:
Cancer Cells: Are cells that have mutated and serve no purpose in the body any more. They can contiune to mitotically divide and form large masses such as tumors which can kill the host. The have an enzyme called telomerase which rebuilds the telomeres after every cell division. This means that cancer cells can divide inifnit number of times so long as they are provided neutrients.