Lecture 21, 10/31 (Maybruck 6); Bacterial Genetics

Here is the audio.

• • Slide 1 of handout from 10/29 – bacterial genetics replication, transcription, and translation
• o The study of bacterial heredity discusses passing of traits to subsequent generations and evolution of genetic material (more on slide one of handout from 10/29)
• • Slide 2 levels of structure and terminology
• o Genome – total amount of genetic material in a cell
• • In bacteria and eukaryotes and viruses the genetic material is DNA. In a retrovirus it would be RNA (ex. HIV)
• o Chromosome – includes genes that are critical for the survival of the bacteria/cell.
• • We have diploid chromosome sets (two copies). 23 chromosomes 2 copies . . . 46 total
• • Haploid have only one copy.
• • Chromosome is supercoiled to save space. For it to be copied it will be unwound by a DNA gyrase.
• o Plasmids – another type of genetic material. Plasmids help but are not essential. They allow the bacteria to adapt to a certain situation
• o Gene – a specific sequence of nucleotides. Found within the chromosome they are a specific sequence of nucleotides that will code for a protein.
• o Genotype – genetic makeup of a gene. Genotype is a specific nucleotide sequence of that gene.
• o Phenotype - The protein that was produced by the gene produces a trait and that is called the phenotype
• • Slide 3 DNA
• o Basic unit of DNA is a nucleotide.
• o Nucleotide – includes nitrogenous base which defines the type of nucleotide we have, They have a phosphate group and a sugar group.
• o Hydroxyl group lacking on the ribose sugar of DNA. If you see a hydroxyl group you know you have an RNA.
• o Each separate strand of the DNA (nucleotide) is covalently bound – unequally shared electrons.
• o The phosphate group is covalently bound to an adjacent nucleotide at the #3 carbon.
• o sugar phosphate linkage occurs on outside of helix
• o you ultimately get the double helix
• • slide 4 DNA
• o purines: adenine and guanine
• o pyrmidines: thymine and cytosine
• o two colons two hydrogen bonds 3 colons three hydrogen bonds. A::T G:::C
• • slide 5+6 DNA replication in bacteria: a semiconservative process
• o semiconservative - formation of a new DNA molecule from old DNA strands
• o STEP 1
• • uncoiling the DNA using DNA gyrase
• • separating the DNA molecule into 2 strands – helped by the enzyme helicase (which goes to “A” “T” rich area which is the origin of replication) and single stranded binding proteins (without these the hydrogen bonds would reattach). The A::T rich sight is the origin of replication – it is easier for the helicase to break down the bonds here.
• • The area where the strands are being split is called the replication fork.
• • Slide 7 DNA replication in bacteria: a semiconservative process
• o In order for the synthesis of new nucleotides to be added to the old DNA strand to form a new DNA strand you need RNA primase and DNA polymerase III.
• o DNA polymerase III – before it can add new nucleotides it needs a primer (RNA primase). It works down the strand adding nucleotides according to what it reads on the old strand. It can only read DNA strand in 3’-5’ direction. SO in order for it to replicate 5’-3’ direction it waits for helicase to open up the two DNA strands wide enough so that an RNA primer can get in. The DNA polymerase III uses it to replicate in the opposite direction.
• o RNA primase – adds complimentary RNA nucleotides
• o Processing of the lagging strand creates okazaki fragments.
• o DNA polymerase I (repair polymerase) - removes all of RNA primers and replace it with the correct complementary nucleotides in the newly synthesized strand.
• • Slide 8
• o DNA ligase – connects okazaki fragments
• o Freesciencelectures.com video DNA replication process
  
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• • Slide 9 transcription and translation overview
• o Gene has a specific sequence of nucleotides that’s going to code for a protein. That DNA within the gene has nucleotides that can be grouped into 3’s (triplets). Each of those groups will code for a specific amino acid. We get a protein that rolls over the DNA and creates an exact copy of the gene in RNA (mRNA). RNA’s grouped together as three is known as a codon (in DNA it is a triplet) which codes for a specific amino acid which is what proteins are made of.
• o DNA → RNA = transcription
• o mRNA → amino acids = translation
• • Slide 10 RNA
• o Look at diagram on the handout.
• o RNA uses uracil (in pyrimidine group) instead of thymine
• • Slide 11 RNA (1 strand of covalently bound nucleotides)
• o mRNA – RNA that is involve in coding for a protein. Provides an exact copy for a gene.
• o tRNA – parts of tRNA that complimentary bind to one another making it look like it has two strands. This creates hairpin structures. On one of the hairpin structures there is a triplet nucleotide sequence. That nucleotide sequence will bind to a specific sequence of mRNA. At the other end of the tRNA a specific amino acid will be attached.
• • tRNA brings the specific amino acid of the mRNA to the codon. It knows because of the anticodon which complimentary binds to the codon.