Dna 4
Dna 4The molecule responsible for the transformation of characteristics form one generation to the next is called DNA. The genetic material, located in the chromosomes is a combination of acid and histones. DNA is made up of units called nucleotides. Nucleotides are made up of 3 components, a five carbon sugar (deoxyribose), a phosphate group, and a nitrogenous base. This base can be either adenine, guanine, thymine or cytosine.
There are 2 strands of nucleotides in a double-helix - they are anti-parallel, meaning they go in opposite directions. Double stranded DNA is located in the chromosome. DNA and proteins together make up chromatin which is foiled and coiled.
DNA makes an exact copy of itself just before cell division begins. This process of DNA duplication is known as replication. The hydrogen bond between the base pairs of the 2 nucleotide strands weaken, and the 2 strands break apart. Each strand acts as a template forming a new nucleotide. This is accomplished by the acting of 2 sets of enzymes - DNA helicase enzymes and DNA polymerase enzymes. The DNA helicase enzymes separate the 2 nucleotide strands. The site where the helicase is working and where replication is taking place is known as the DNA fork. The polymerase enzyme helps the nitrogenous base in a given nucleotide to pick up and attach to a complementary base at the 3' end of the DNA template. The 5'-3' strand of template is duplicated in short segments called Okazaki fragments. Ligase is the enzyme that joins the fragments together. The end product of this is an exact copy of the original DNA.
DNA must also be stable, but able to be changed. We know that DNA is stable because of the tightly wound, double helix ladder formation. Also the bonds that keep everything together are hydrogen bonds, one of the...
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