This is a DNA :DLet's start with the word chromotin. A chromotin is a long thread-like material that is actually a form that DNA takes withing the nuclei of a nondividing cell. In other words, a chromotin is a piece of DNA with activated genes. A chromosome is the form that a chromotin takes when it is going to divide. This can easily be seen under a microscope.
A gene is a piece of DNA that contains information for an amino acid sequence to make proteins. In turn, it also can code for a trait.They are primary for making proteins. Genome is the total number of all genes in the body. There are about 25,000 different types of genes. Interesting enough, it has been recently discovered that a single gene can code for a number of different polypeptide chains. That first picture above is a piece of DNA that is considered to be a gene and can contain a code for different proteins. Proteome is the number of different proteins produced in the body. There are about 100,000 proteins in the body!! Wow! Despite the fact that these are some pretty high numbers scientists estimate that there are only 300 genes active in a given cell at a given time and the genes that are functioning in certain cells can be temporarily shut off and later turned back on. Some genes can also be permenantly inactivated in each specialized cell type. This is important because different tissues and organs require that certain genes need to be turned off while others need to be permenantly turned on.
When a cell is going to divide, DNA must be copied prior to its cell division. This is called DNA replication. This can be a very confusing process so I will write it in steps. Refer to the picture above so you don't get lost!!
- An enzyme moves along the DNA breaking the hydrogen bonds between each pair bases of nucleotides. Its like the enzyme is a zipper and its unzipping the DNA along the hydrogen bonds.
- The now single strand of DNA is now floating withing the nucleus. Along with this strand are free floating nucleotides that then bind with the complementary nucleotides of the old strand.
- Adenine-> Thymine
- Guaine-> Cytocine
There are two types of cell division: Mitosis and Meiosis. For this session I will only talk about mitosis. I will have a different section dedicated to meiosis when I have a reproduction section. When a cell divides it has the exact same identity as the parent cell. This is when the chromotin convert themselves into chromosomes. I will put the steps of mitosis in number order along with a picture.
- Interphase- this is when the DNA replicate (not shown in picture but it IS there at the beginning so dont forget; cells have to replicate before dividing!)
- Prophase- the chromotin condense themselves into chromosomes; the duplicated chromotid on one side and the original on the other. They look like large "X"s. Also, the nuclear envelope fades away but don't worry it is still somewhat there!
- Metaphase- the chromosomes line up in the equator of the cell (the middle). An organelle called centrioles form spindle fibers that attatch to the center of the chromosome called the centromere.
- Anaphase- the spindle fibers then pull the duplicated chromosomes to opposite poles.
- Telophase- finally, the chromosomes are pulled apart so much that the cell cytoplasm breaks apart thus creating two new cells. The chromosomes turn back into chromotin and the nuclear envelope reappears concealing them.
These notes were based off of actual notes from myself while I was in the class and further research outside the class. I also used the notes from my AWESOME professors who kindly handed them down to me and contributed extra information about this section. This information was also checked and clarified from various physiology books. For the pictures, I do not own any rights to them! If you have any questions feel free to ask on my blogspot or email me!
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