overview of notess for Final

overview of notess for Final - 3 Ways in which genes are...

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3 Ways in which genes are transferred between bacterial cells -bacterial conjugation -Bacterial transformation -Transduction F plasmid is an episome -they can actually integrate into the cell’s DNA Multiplicity of infection -more than one phage infects a single bacterial cell. Rare because of low concentration of phage in environment Recombination can occur between phage genomes in this situation Generalized transduction Specialized transduction -involves temperate phages (lamda is example) Conditional mutants important -permissive conditions -restrictive conditions Seymore Benzer’s rII system for detecting rare crossover events -rII loci of phage T4 -r = rapid lysis so large plaques -Grow on E.coli B -no growth on E. coli K Cell Theory: 1. All living things are composed of cells 2. At this point, all cells come from pre-existing cells Temperate phage -lytic cycle -lysogenic cycle -The T even phages are not temperate phages and therefore can only do generalized transduction -lamda phage carries the recombinant enzyme somewhere Precursor-> enzyme X-> ornithine-> enzyme Y-> citrulline-> enzyme Z->arginine Active site: 1.Provides template -To bring the reactants to the proper position 2. Induced fit my astress bonds in the substrate. 3. Favorible microenvironment (pH, charge) 4. Direct participation (brief covalent bonding to active site aa side chain). Bead Theory -Gene is recognized through its mutant alleles -A mutant allele affects a single phenotypic character -It maps to one chromosome locus -It shows a Mendelian ratio when intercrossed.
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The gene is viewed as the fundamental unit of structure. It is indivisible by crossing over -Benzer falsified The gene is the fundamental unit of change A mutation changes the whole gene, not part. -Benzer showed you could change individual parts The gene is the fundamental unit of function. Parts of a gene cannot function. Benzer found the minimal proportion between a pair of different mutant alleles to be 0.01%. Therefore, the map distance between individual base pairs appears to be 0.01 m.u. Deletion mapping -A deletion is a mutation which results from the loss of a portion of the DNA. -A point mutation on one chromosome cannot produce a wild type by recombination with the deleted portion on another chromosome. Benzer asked if all site equally mutable. -Benzer mapped 1612 point mutations in the rII locus. -All sites within a gene are not equally mutable there are hot spots of mutation. -Using Poisson distribution Benzer showed that at least 60 sites were more mutable than those with 1 or 2 mutations. Mutagenic agents produce different hot spots 1. Each mutagen can act in a specific way a. Ex. UV light can fuse 2 thymines 2. Don’t effect the purines the same way Anaximander, 6 th century B.C., humans and other animals were decended from fishes. (500 B.C.)
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overview of notess for Final - 3 Ways in which genes are...

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