Week 7 Notes
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This 4 page Class Notes was uploaded by Jacob Edwards on Wednesday October 12, 2016. The Class Notes belongs to 1030 at Clemson University taught by Dr. William Baldwin in Fall 2016. Since its upload, it has received 7 views. For similar materials see General Biology in BIO at Clemson University.
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Date Created: 10/12/16
Week 7 Notes Genetic Material o Molecular Biology Study of heredity at the molecular level o Viruses Not considered to be alve Not Cellular Cannot reproduce on their own Infect organisms Binding to receptors on a host’s target cell Injecting viral genetic material into the cell Hijacking the cell’s own molecules and organelles to produce new copies of the virus Host cell is destroyed, and cycle continues o DNA and RNA RNA uses ribose instead of deoxyribose Uses uracil instead of thymine Watson and Crick found that DNA has a double helix structure A pairs with T to form two hydrogen bonds (DNA) G pairs with C to form three hydrogen bonds (DNA) o DNA Replication Follows a semi conservative model Two DNA strands separate Each strand is used a s a pattern to produce a complimentary strand Each new DNA helix has one old strand with one new strand Two key proteins in replication DNA ligase o Joins small fragments into a continouos chain DNA polymerase o Adds nucleotides to a growing chain o Proofreads and corrects base pairing Central Dogma o DNA makes RNA makes protein Transcription The synthesis of RNA under the direction of DNA Translation The synthesis of proteins under the direction of RNA Triplet Code The genetic information for an amino acid sequence of a polypeptide chain are written in non overlapping three base words called a codon In mRNA 64 possible codons Some amino acids have more than one possible codon Three nucleotides specify one amino acid AUG codes for methionine and signals the start of translation 3 “stop” codons signal the end of translation Gentic code Redundant o With more than one codon for some amino acids Unambiguous o In that any codon for one amino acid does not code for any other amino acid Nearly Universal o Genetic code is shared by organisms from the simplest bacteria to the most complex plants and animals Without Punctuation o Codons are adjacent to each other with no gaps in between Transcription produces genetic messages RNA nucleotides are linked by the transcription enzymes RNA polymerase The “start” signal for transcription is called a promoter Transcription Phases Initiation o RNA polymerase attaches to the promoter Elongation o RNA grows longer, as RNA peels away, the DNA strands rejoin Termination o RNA polymerase reaches a sequence of bases in the DNA template called a terminator, which signals the end of the gene Transfer RNA (tRNA) Act as a language interpreter o Convert the genetic material of mRNA into the language of proteins Do this by: o Picking up the appropriate amino acid o Using a special triplet of bases called an anticodon to recognize the appropriate codons in the mRNA Ribosomes build polypeptides Translation occurs on the ribosomes o Ribosomes Coordinate the functioning of mRNA and tRNA and, ultimately the synthesis of polypeptides Have two subunits: small and large Each subunit is composed of ribosomal RNAs and proteins Subunits come together during translation Ribosomes have binding sites for mRNA and tRNAs Translation Phases Same as Transcription Initiations o An mRNA molecule will bind to a small ribosomal subunit and the first tRNA binds to mRNA at the start codon (AUG) o The large ribosomal subunit joins the small subunit, allowing the ribosome to function o The first tRNA occupies the P site which holds the growing polypeptide chain o The A site is available to receive the next tRNA Elongation o Codon Recognition Te anticodon fo incoming tRNA molecule, carrying its amino acid pairs with the mRNA codon in the A site of the ribosome o Peptide bond formation The new amino acid is joined to the chain o Translocation tRNA is released from the P site and the ribosome moves tRNA from the A site to the P site o Continues intil the ribosome reaches a stop codon Mutations Any change in the nucleotide sequence of DNA Two Categories o Base Substitutions Have no effect at all, called a silent mutation Change the amino acid coding producing a missense mutation which produces a different amino acid Change an amino acid into a stop codon producing a nonsense mutation o Deletions or Insertions Alter the reading frame of the mRNA so that nucleotides are grouped into different codons Produce a nonfunctional polypeptide o Mutagenesis is the production of mutations o Mutations can be cause by mutagens Radiation Chemicals Virus and Bacteria Genetics o Viruses are wrapped in a protein coat called a capsid `Two reproductive systems Lytic Cycle o Viral particles are produces using host cell components o The host cell lyses and viruses are released Lysogenic Cycle o Viral DNA is inserted into host chromosome by recombination o Viral DNA is duplicated along with the host chromosome during cell division o The inserted phage DNA is called a prophage o Morst prophage genes are inactive o Environmental signals can cause a switch to the lytic cycle, causing the viral DNA to be exercised from the bacterial chromosome and leading to the death of the host cell Emerging Viruses Viruses that appear suddenly or are new to medical scientists Three processes contribute to this o Mutation o Contact between species o Spread from isolated human populations to larger human populations often over great distances AIDS is caused by HIV o HIV is an RNA virus Has two copies of its RNA genome Carries molecules of reverse transcriptase which causes reverse transcription producing DNA from an RNA template o
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