ALL ABOUT DNA

Discovery of the Structure of DNA
     In 1928, Frederick Griffith discovered that a factor (which would later become DNA) in diseased bacteria could transform harmless bacteria into deadly bacteria. He conducted his experiment using mice. The DNA in the harmless bacteria would become lethal because both bacteria had the same DNA, so, when exposed to each other, the lethal DNA turned on genes in the harmless DNA that made it lethal, thus altering its DNA to be similar to the deadly bacteria. In 1952, Rosalind Franklin took the very first picture of DNA, and she would not share her findings with any other scientists. In 1953, two scientists, Watson and Crick, needed Franklin's photo of DNA to prove that DNA was a double helix, but, since Franklin would not show her picture of the DNA, the men stole it. To get the picture of the DNA, Franklin used x-rays, and, unfortunately, there was not enough information about the consequences of standing in front of an x-ray without lead protection, so she developed cervical cancer. Before Franklin died of cancer, Watson and Crick published their findings of DNA, giving little credit to Rosalind Franklin, and they received the Pulitzer Prize. Because of prevalent sexism in America in the mid-20th century, Franklin received no compensation for her photograph and died before she, too, was awarded the Pulitzer Prize.
Structure of DNA
-Double Helix: The shape of DNA, which appears to be a winding (or spiral) staircase.
-Deoxyribose: The five carbon sugar found in DNA.
-Nucleotides: The subunits of DNA that is made up of three parts; phosphate, five carbon sugars (aka Deoxyribose), and the base.
-Nucleic acids: Genes or specific traits.
     DNA is made up of repeating molecules called nucleotides. Three nucleotides create a codon, which codes for a specific amino acid. (Amino acids are the building blocks of DNA.) There are four types of nitrogen bases that make up nucleotides: Adenine (A); Guanine (G, not to be confused with guano!); Thymine (T); and Cytosine (C). With these nitrogen bases is the Base-Pairing Rule, which states that Adenine always pairs up with Thymine (which are called Purines) and Cytosine and Guanine always pair up (which are called Pyrimidines). When A and T bond and C and G bond, the two strands are called complimentary bonds. Between the complimentary bonds, hydrogen bonds form, weak bonds, which easily separate for reproduction. The genetic information in the DNA is stored as a sequence of bases (nucleotides), and the order of the bases determines the genetic information.
How Does DNA Replicate?
       Replication is used to make a copy, occurs in the nucleus of cells, and is used to prepare for cell division. The complimentary structure of DNA helps it to make copies of itself. Replication occurs in three steps:
1) DNA helicase unzips:
   -Helicase, an enzyme, splits the complimentary strands by breaking the hydrogen bonds that linked the nitrogen bases.
2) DNA polymerase:
   -Polymerase, also an enzyme, adds new nucleotides to the exposed nitrogen bases.
3) The two new molecules separate when both are complete.

As a result of Replication, the DNA molecules produce two identical new complimentary strands. Each strand of the original DNA serves as a template for the new strand.
What's RNA?
     RNA is similar to DNA because it has a single strand of nucleotides and also has complimentary strands, but it has ribose instead of Deoxyribose and uses Uracil (U) instead of Thymine (T). Although U is used instead of T, Uracil will still pair with Adenine.
How Does DNA "Make" Protein?
      In its simplest sense, expressing a gene means manufacturing its corresponding proteins, and it's a multilayered process between Transcription and Translation. Transcription is the creation of RNA, which is the message from the DNA created during Transcription. Transcription occurs in the nucleus and is used because it is the process involving the transcribing of genetic information from DNA to RNA. When a gene is activated, the DNA strands separate and one of them serves as a template for copying a messenger RNA (which is called mRNA). Transcription occurs in three steps:
1) RNA polymerase binds to DNA.
2)Elongation:
   -DNA strand unwinds and polymerase allows RNA to transcribe only a single strand.
3)Termination:
   -RNA releases and detaches from the DNA strand
Translation is the actual creation of a protein (called polypeptide) under the direction of RNA. The mRNA is "read" according to the genetic code. Translation occurs in the cytoplasm with the ribosomes of cells, and it is used to put the amino acids together to make proteins (mRNA-tRNA-amino acids). Each group of three base pairs in mRNA makes a codon, and each codon specifies for a particular amino acid. The mRNA sequence is used as a template to assemble (in order) the chain of amino acids that form a protein. Transfer RNA (called tRNA) attaches and transports amino acids nto growing chains to form proteins. Basically, the tRNA is already present in the ribosome and attaches free amino acids into one growing structure. TRNA functions as an interpreter for nucleic acid and peptide sequences, and tRNA picks up amino acids and matches them to the proper codons in mRNA. TRNA is complimentary to mRNA.
What Are Genetic Mutations?
     Mutations are permanent changes in the DNA sequence, and mutations can occur in two ways:
1) Mistakes that occur when a cell copies its DNA:
   -such as in cellular division
2) Acquired during a person's lifetime:
   -ex: environmental factors (UV light, chemicals, radiation)
Mutations generally occur in somatic cells, but can not be passed on to the next generations. The actual number of mistakes that remain incorporated into the DNA is low, because cells contain special DNA repair proteins that fix many of the mistakes in the DNA that care caused by mutagens (aka mutation-causing agents). There are eight types of genetic mutations:
1) Base-Pair Substitutions (genes):
    -known as "silent mutations"
    -they have no effect on proteins
2)Missense/Substitution:
  -substitutes a different amino acid  for the correct amino acid
  -it results in a different protein
3)Nonsense:
  -substitutes to a stop codon
  -results in a nonfunctional protein
4) Deletion:
   -changes the number of DNA bases by removing a segment of DNA
(The following are chromosomal genetic mutations)
5) Duplication:
   -multiple copies of all chromosomal regions are created
6) Inversion:
   -reverses the orientation of a chromosomal segment
7) Insertion:
   -changes the number of DNA bases by inserting a segment of DNA
   -can disrupt the grouping of codons
          •resulting m a completely different translation from the original
          •the earlier in the sequence the deletion/Insertion occurs, the more altered the produced protein is
8) Translocation:
   -interchange of genetic parts from nonhomologus chromosomes
         •chromosomes occur in pairs (one from each parent)
         •nonhomologus would be Chromosome Four exchanging a DNA segment with Chromosome Twenty.