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EXAM FOUR NOTES |
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Molecular Biology Introduction Definitions History Central Dogma Definitions Chromosomes DNA Gene Genotype Phenotype Chromosomes The structure in cells that carries hereditary
information Composed of DNA and protein Prokaryotic - circular Eukaryotic - linear DNA Nitrogenous base (4 bases - A,T,G & C Deoxyribose sugar Phosphate Double helix structure Genes Segments of DNA Functional or regulatory Complementation Mutability and variation Genotype The genetic make-up of an organism; the information that
codes for all the characteristics of an organism Phenotype The expression or physical manifestation of a gene; how
it appears Molecular biology seeks to understand the molecular or chemical
basis of genetics History of molecular biology is a melding of biochemistry, especially
nucleic acid biochemistry and genetics Biochemistry Meischer Avery & MacLeod Hershey & Chase Watson & Crick Genetics Mendel Morgan Delbruck Beadle & Tatum Tatum & Lederberg Genetics Mendel (1865) Fluid vs. particulate inheritance Studied pure breeding pea plants Law of Segregation Law of Independent Assortment Rediscovered by de Vries &
others Genetics Morgan developed modern science of genetics, especially
techniques of mapping genes on chromosomes used fruit flies because they had a shorter generation
time than peas Genetics discovered transformation in 1927 a process by which a nonpathogenic strain is transformed
into a pathogenic strain Genetics Delbruck developed quantitative methods for analysis of bacteriophage organized course to teach biologists methods at Genetics Beadle & Tatum developed Neurospora as an
experimental organism established one gene one enzyme hypothesis complementation testing generation time is even shorter with Neurospora Genetics Tatum & Lederburg discovered conjugation in bacteria Biochemistry Meischer (1869) Austrian doctor isolated a substance called “nuclein”
from the nuclei of cells obtained from the pus of surgical bandages found to contain nitrogenous chemicals, sugar and
phosphate Biochemistry Avery & MacLeod (1944) isolated characterized transforming factor using highly purified
enzymes found transforming factor to be DNA Biochemistry Hershey & Chase (1952) used newly developed radioisotopes S35 for protein P32 for nucleic acid labeled bacteriophage (a virus
of bacteria) found P32 went into cells but S35 did not implying that
nucleic acid transfer information to cell for new bacteriophages Biochemistry Watson & Crick (1953) used X-ray crystallograph to
study structure of DNA by combining chemical data and X-ray data were able to
construct a model of DNA structure inferred function leading to Central Dogma Central Dogma DNA Structure Genetic Code Replication Transcription Translation DNA Structure Sugars Bases Phosphates Double Helix Anti-parallel Genetic Code 4 bases / 20 amino acids codons punctuation Central Dogma states a hypothesis regarding information flow in cell Replication - the copying of DNA or information for next generation Transcription - the copying of information for use by the cell Translation - the conversion of information into useful products
-enzymes Replication replication is semi-conservative replication occurs at replication fork replication is discontinuous process uses DNA polymerase requires a primer Transcription RNA polymerase promoters produces messenger RNA (mRNA) requires NO primer Translation tRNA amino acid synthase ribosomes initiation termination |
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Microbial Genetics - DNA
Transfer Review of Information Transfer in Cell Recombination Transfer of DNA &Genetic Recombination in Bacteria Conjugation Transformation Transduction Microbial Genetics - DNA
Transfer Recombination - exchange of DNA between two DNA molecules to form new combinations Crossing over Occurs when DNA is transfer from one cell to another (transfer from a doner to a recipient) Microbial Genetics -
Regulation Three types of regulation Constitutive - gene is always turned on Repression - gene is normally turned on but can be
turned off in response to a metabolic signal Induction - gene is normally turned off but can be
turned on in response to a metabolic signal Microbial Genetics -
Regulation Types of Regulation of mRNA synthesis Induction - lac operon Repression - trp operon Microbial Genetics -
Regulation Microbial Genetics -
Mutation Mutation - Introduction A mutation is a change in the DNA sequence that results
in a change in the product protein Mutations can be neutral, harmful (most) or beneficial Mutation is the basis of variation within a species and
thus provides an important mechanism to evolution Types of Mutation Base-pair substitution - misssense
change in amino acid sequence Base-pair substitution - nonsense change in DNA sequence
- premature stop Frameshift Insertion Deletion Normal gene DNA transcribed mRNA translated No change in gene product Missense mutation Base substitution Changes amino acid sequence by one amino acid May or may not affect activity of protein Nonsense mutation Mutation changes codon to stop
codon Premature termination of protein Almost always destroys activity of protein Frameshift mutation inserts or deletes a base in the DNA Protein may be of correct size (approximately) Protein sequence altered significantly Mutatgens Chemicals that modify DNA Deaminating agents Methylating agents Intercalating agents Radiation UV - UV repair system X-Rays Frequency Rate at which change occurs usually low Mostly random although there are “hot spots” Low rate necessary to provide genetic diversity Rate can change depending upon what population of cells
is exposed to |
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Biotechnology Introduction Tools Process Applications Biotechnology Introduction Gene is
identified and excised from one organism Gene is placed
in vector (plasmid) and amplified Gene is
transferred to new organism or used in host organism to make protein product Biotechnology - Tools Restriction endonucleases Nucleases
cut nucleic acid – at first seem non specific Linn
& Abner discover that some strains of bacteria
are able to resist bacteriophage infection by
digesting infecting DNA Different
bacteria produce different restriction enzymes Restriction Endonucleases Cut at
specific 4, 6, or 8 base sites Site is a
“palindrome” Racecar Madam I’m
Adam Damit I’m Mad Some
restriction enzymes generate “sticky ends” Plasmids Carry an
antibiotic resistance marker Carry
restriction sites in convenient locations to insert DNA Carry
characteristics that allow the plasmid to reproduce in several organisms Polymerase Chain Reaction (PCR) Allows
any segment of DNA to be amplified chemically in minutes Uses a thermostable DNA polymerase Machine
can cycle every 60-90 seconds Agarose Gel Electrophoresis Can
separate DNA fragments made with restriction enzymes Can
separate PCR made DNA Can be
used to sequence DNA Biotechnology - Process Basic
process worked out by Cohen & Boyer Cut
plasmid DNA and target DNA with same restriction enzyme Mix DNA and
allow sticky ends to match up Select
DNA clones having target gene |
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