DNA

__**DNA**__ Yi En and Kevin

What is DNA and where is it found? DNA is like the brain of the cell. It tells the cell what processed to carry out and how it should do it. DNA is found throughout the body inside chromosomes which is found in the nucleus of cells. It is always in the nucleus of cells.

What does it look like (its structure) and what is it made from? DNA it self looks like a spiral ladder which is also known as a double helix. It is made from 4 main bases aligned inside of phosphate and sugar. The four nitrogen bases that carry the genes are Thymine, Cytosine, Adenine, and Guanine. Phosphate and deoxyribose sugar form the structure and is the backbone for DNA. The four nitrogen bases are connect in pairs by hydrogen bonds, making up the rungs of the ladder. Thymine will always pair with adenine while cytosine will always pair with guanine.

media type="youtube" key="121ScQj8dIs" height="315" width="420" http://www.youtube.com/watch?v=121ScQj8dIs&feature=g-vrec

How and why does DNA copy itself? DNA will copy itself when cells split to allow continued growth. Each cell needs the same set of DNA. Hence, DNA copies itself when the cells are going to split. There are three stages to the process: interphase, mitosis, and cytokinesis. During interphase, the cell grows to its mature size, makes a copy of its DNA, and prepares to divide into two new cells. Two cylindrical structures called centrioles are also copied. In mitosis, the chromatin in the nucleus condenses to form chromosomes. The pairs of centrioles move to opposite sides of the nucleus. Spindle fibers form a bridge between the ends of the cell and the nuclear envelope breaks down. The chromosomes line up across the center of the cell, each chromosome attaches to a spindle fiber at its centromere. The centromeres split. The two chromatids separate, and each chromatid becomes a new chromosome. The new chromosomes move to opposite ends of the cell. The cell stretches out as the opposite ends are pushed apart. The chromosomes begin to stretch out and lose their rod like appearance. A new nuclear envelope forms around each region of chromosomes. In cytokinesis, the cell membrane pinches in around the middle of the cell. The cell splits in two. Each daughter cell ends up with an identical set of chromosomes and about half the organelles.

media type="youtube" key="teV62zrm2P0" height="315" width="420" http://www.youtube.com/watch?v=teV62zrm2P0

What are genes and where are they found? Genes are pieces of DNA that have the code for a specific protein. Genes are small sections of a chromosome that controls one specific characteristic. Bases in the gene determine the order in which amino acids are put together to create the protein. Proteins have specific functions in the body so it is important that the right proteins are made. Genes are found in a cell’s nucleus, where the chromosomes are located. The chromosomes themselves are made up of DNA molecules.

media type="youtube" key="eOvMNOMRRm8" height="315" width="420" http://www.youtube.com/watch?v=eOvMNOMRRm8

=__**The Replication Of DNA:**__=

Original: DNA is complete, getting ready to replicate.

Un-Zipping: The DNA splits, and the hydrogen bonds loosen.

DNA completes itself: Floating nitrogen basses are attached to the split DNA.

The resulting DNA is an exact copy of the original.

A DNA Replication Video:

media type="youtube" key="cDlKrLJjRlY" height="315" width="420" (Don't pay attention to U, its for RNA) http://www.youtube.com/watch?v=cDlKrLJjRlY