Embryonicstem cells are pluripotent cells which are found in the inner cell mass ofblastocyst-stage embryos. These are maintained and in culture up until the timethey are needed.Whenthe embryonic stem cells are in culture, they must be grown under suitableconditions in order for them to remain undifferentiated. However if they clumptogether they will form embryoid bodies.
Theybegin to differentiate unexpectedly. This means they can form muscle and nervecells. Impulsive differentiation suggests that the culture of embryonic stemcells is healthy. This process enables the generation of specific types ofdifferentiated cells like heart muscle cells and blood cells. Nonetheless, tomake these cultures scientists attempt to control the differentiation of stemcells by changing the chemical composition of the culture medium and alter thesurface of the culture dish. They can also interrupt the differentiationprocess by modifying the cells by inserting specific genes. 3.
2Cell division does not take place byrandom chance. The cell divides according to the conditions in its environmentand genetic code. Cells receive extracellular chemical signals from the body orother cells that will cause them to start dividing. These chemical signals areknown as mitogens. In addition, other cells can release chemical substanceswhich will cause nearby cells to divide. One of these is cytokines. Cytokinesare a type of signaling molecule and are mainly used for intercellularcommunication. These are molecules which are produced in cells of the immunesystem and also in the nervous system.
Cells can also be induced intodividing due to growth factors. The surface of the cell membrane has differentreceptor regions for specific regulatory proteins. When the receptor region isfilled with the protein it then sends a signal that activates proteins withinthe cell and results in cell division to begin.Thecell cycle is not a linear pathway because in the end the two daughter cellscan start the same process again from the beginning.Interphone is very first the stage where thecell grows and makes a copy of its DNA. Then leading to the mitotic phase wherethe cell will separate the DNA into two copies, dividing the cytoplasm formingtwo daughter cells. The process of interphase has three phases.
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The first phaseis called the G1 (growth phase) which is the longest phase. The cell grows larger as in double its size and copiesorganelles. Here is where the cytoplasm increases in volume. It also produces molecularbuilding blocks for the next two phases. ATP is synthesised to provide energyfor replication. Finally the cell will remain in this phase if the cell is notgoing to divide. In the second phase which is known as the S phase wheresynthesis occurs to create sister chromatids.
The cell duplicates by the processof semi conservative replication. Semi conservative replication is when a double stranded DNA molecule separates and each strandis used as a template for the synthesis of a new strand. Producing twoidentical copies of the original double stranded molecule. The third phase is G2(growth 2) is a short gap before mitosis in which the cell resumes its growth by making moreproteins and organelles in preparation for mitosis. Also the cytoskeleton ofthe cell breaks down and the protein microtubule components begin to reassembleinto spindle fibres.3.
3Mitosis is a form of celldivision where a cell divides to generate two daughter cells which aregenetically identical to that same cell. The purpose of mitosis is to grow andrepair damaged a cell, that’s how wounds heal. There are four significantphases firstly, to begin with prophase. In prophase, chromosomes condense andbecome visible. The chromosomes coil becoming shorter and fatter. The nucleolusdisappears and the nuclear envelope breaks down. The centrioles move toopposite poles of the cell.
Each centriole forms spindle fibers. The mitoticspindle forms it’s made of strong fibers called microtubules. The spindleorganises the chromosomes and moves them around when necessary. Next, inmetaphase one or more spindle fibres attach to the centromere of eachchromosome. The chromosomes are then pulled along the spindle apparatus andarrange themselves across the equator of the cell. Anaphase is the third phaseof mitosis where the centromeres divide into two and spindle fibres shorten,pull and contract one of each pair of sister chromatids to opposite poles ofthe cell. Now each pole will have the exact same number and type of chromosomes.The chromatids will now be called chromosomes.
Also the energy fro this processis provided by the mitochondria during aerobic respiration. The last stage ofmitosis is telophase where thecell is almost towards the finish line of dividing, and it starts to reform itsnormal structures as cytokinesis occurs. The spindle is broken down.
Then twonew nuclei form with the nuclear membranes and nucleoli reappearing. Andeventually chromosomes decondense and return to their original form. Just to finishthe whole process of cytokinesis, the cytoplasmdivides into two and we have two new cells, each with a complete set ofchromosomes identical to those of the original cell we started with.
