Microbial Genetics.docx

Transformation Experiment The smooth bacteria contained the virulent strain of DNA, while the rough bacteria had the avirulant strand of DNA. When injected individually into one mouse, the smooth bacteria killed the mouse. When injected individually into one mouse, the rough bacteria did not kill th...

Transformation Experiment The smooth bacteria contained the virulent strain of DNA, while the rough bacteria had the avirulant strand of DNA. When injected individually into one mouse, the smooth bacteria killed the mouse. When injected individually into one mouse, the rough bacteria did not kill the mouse. However, due to the smooth strain using transformation of its DNA into the rough strain, once a combination of both the smooth and rough strain were injected into the same mouse, the mouse would die. Transformation is a way for bacteria to acquire new genetic markers via the incorporation of new DNA to their genetic material. Genetic Material The genetic material of organisms is described to be nucleic acid. Nucleic acid is composed of nucleotides. Nucleotides are a combination of a nitrogenous base, 5-carbon sugar, and (up to 3) phosphate (groups). The 5-carbon sugar of the nucleotide can either be deoxyribose (in DNA) or ribose (in RNA). Nucleotides are what make up the stair-like spiral structure within DNA. Nucleic Acid Structure Purines Purines include adenine, and guanine. Purines are composed of 2 fused carbon rings with 5-6 members. Elements within the purine nitrogenous base are labeled numerically from 1-9. In purines, the nitrogenous base, at N9, is attached to the sugar molecule via a glycosidic bond. Pyrimidines Pyrimidines include thymine, cytosine, and uracil. Pyrimidines are composed of a 6 carbon ring. Elements within the pyrimidine nitrogenous base are labeled numerically from 1-6. In pyrimidines, the nitrogenous base, at N1, is attached to the sugar molecule via a glycosidic bond. Sugar vs Nitrogenous Base Nomenclature Sugar When numbering the elements within a sugar molecule, a prime symbol is attached to the number of each carbon element. For example, the carbon on the sugar molecule that is attached to the nitrogenous base is considered to be the 1st carbon and would be called: 1’. Nitrogenous Base When numbering the elements within a nitrogenous base, nothing is attached to the number, rather they are simply numbered in numerical order or may have a “N” placed in front of the number. For example, the first carbon element on a nitrogenous base is called: “1” or can also be called “N1”. Nucleoside vs Nucleotide Nomenclature Adenine is the base. Adenosine is the nucleoside. Adenylic acid is the nucleotide. Guanine is the base. Guanosine is the nucleoside. Guanylic acid is the nucleotide. Cytosine is the base. Cytidine is the nucleoside. Cytidynic acid is the nucleotide. Thymine is the base. Thymidine is the nucleoside. Thymidynic acid is the nucleotide. Uracil is the base. Uridine is the nucleoside. Uridynic acid is the nucleotide. DNA Structure Adenosine (A) always pairs with thymine (T) using 2 hydrogen bonds. Guanine (G) always pairs with cytosine (C) using 3 hydrogen bonds. The use of 3 hydrogen bonds as opposed to the 2 hydrogen bonds with A&T, allows the G&C bond to be stronger and more difficult to break. DNA is double stranded, in comparison to RNA which is single stranded. Only DNA uses Thymidynic acid. DNA has A&T pairing. DNA has a nuclear location. DNA is stable. RNA Structure RNA has 3 types: mRNA (messenger RNA), tRNA (transfer RNA), rRNA (ribosomal RNA). Only RNA uses Uridynic acid. RNA has A&U pairing. RNA has a cytoplasmic location. RNA is labile. The Central Dogma The Central Dogma states that DNA is converted to RNA via transcription, followed by RNA being converted to Protein via translation. In some cases, RNA can be converted to DNA via reverse transcription. In translation, there are 4 nucleotides within a codon, and 20 amino acids total. DNA acts as the coding and the template strand within this process. Coding (sense) strand The coding strand has the same sequence as mRNA. DNA is from 5’ to 3’ in the sense strand. Templet (antisense) strand The templet strand guides the synthesis of mRNA via complementary base pairing. DNA Replication DNA replication is semi-conservative, resulting in a parent and a daughter strand. The lagging strand will result in Okazaki Fragments which are not present in the leading strand. DNA Replication Steps Step 1: Helicase unwinds the parental double stranded DNA. Step 2: A protein stabilizes the unwound single stranded DNA. Step 3: The leading strand is continuously synthesized in the 5’-3’ direction by DNA Polymerase. At the same time, the lagging strand is being synthesized discontinuously by DNA Polymerase, resulting in Okazaki Fragments. Step 4: Only in the lagging strand, Ligase is used to fill in the gaps present within the Okazaki Fragments. Eukaryotic vs Prokaryotic Transcription Prokaryotes Prokaryotic cells are polycistronic. Prokaryotes don’t use polyadenylation. Prokaryotes do not have introns. Prokaryotes only have one RNA Polymerase. Prokaryotes lack 5’ caps. Eukaryotes Eukaryotes are monocistronic. Eukaryotes utilize polyadenylation at the 3’ end. Eukaryotes remove their introns. Eukaryotes utilize RNA Polymerase 1, 2, and 3. Eukaryotes have a methylated cap on the 5’ end. Mutations Mutations are the presence of any change within the DNA sequence. Mutations can be spontaneous or induced. Mutations can happen to any DNA base pair. Mutagens can directly modify a base or can be inserted into the nucleic acid, altering it. Mutation types include: Silent mutation Silent mutations involve a base change that has no impact on the amino acid associated with the codon. For example, the codon CGA is altered to AGA but both code for the amino acid Arg. Missense mutation Missense mutations involve a base change that will change the amino acid associated with the codon. Given that each amino acid has it’s own unique properties, a change in the amino acid used, will impact the overall function of the protein synthesized. For example, the codon CUU is altered to CCU, changing the amino acid from Leu to Pro. Nonsense mutation Nonsense mutations involve a base change that will change the amino acid into a Stop codon. Inserting a Stop codon sooner than what would have happened without the mutation, results in a prematurely terminated sequence. For example, the codon UAC is altered to UAA, changing the amino acid from Tyr to a Stop codon. Frameshift mutation Frameshift mutations involve the addition or removal of a base, altering the normal 3 base pairs per codon. For example, the base “C” is inserted into the codon “UUU”, now making the whole sequence “CUUU”.