bio 207 lecture 8.docx

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Biology (Biological Sciences)
Lesley Harrington

BIOL207 B01 Lec08 2014-01-22 CHAPTER 4 (cont’d) A. Mutation Classification (cont’d); a. point mutation (substitute one base for another) b. insertion or deletion (indel); c. effect on gene function (Muller moprhs) i. amorph = null = no wt protein function; complete loss of functions; if there is a stop codon at the start of the gene and it is not made, that would be a null ii. hypomorph = partial loss of wt function; partial loss of function; perhaps the catalytic site has changed so it is not as strong as it was before; not a complete loss of function, but some functions iii. hypermorph= more of the wt function than in wt; more of the mutant function is present than the wildtype; you make a darker purple flower than the typical purple flower; can be a mutation in the catalytic site making the purple proteins faster; this gene has more of the function than the wildtype; VERY RARE iv. neomorph = a new function that is different from wt; not more, not less, it’s just a whole new function; changing the purple flower to a pink flower, a new function, a function that’s different from the widltype v. antimorph = a new function that works in opposition to wt d. loss-of-function (amorph, hypomorph) vs. gain-of-function (hypermorph, neomorph, antimorph); antimorph looks like an amorph, but it works against the wildtype; antimorph is a loss of a wildtype function but antimorph can gain a new function; wildtype protein is still made but there is a mutation that givesANOTHER GENE a different function as well; look phenotypically null, but it’s working in opposition, maybe it degrades the substrate; VERY RARE!; haven’t lost the wildtype function but gained a new function working against the wildtype function; e. amorph, hypomorph tend to be recessive because wt alleles tend to be haplosufficient; wildtype alleles tend to be haplosufficient’most amorphs and hypomorphs are recessive f. hypermorph, neomorph, antimorph tend to be dominant; dominant/ new functions/ opposition functions tend to be dominant; g. Loss of function tends to be recessive, gain of function tends to be dominant; B. Mutant screening: Salvation of Doug a. learn about almost any biological process by identifying mutants that disrupt that process; randomly pick and mutate genes then observe the effects b. mutagenize (chemical, physical, biological) thousands of individuals; mutagenize gametes/ adults (e.g. fruit flies), we wonder what we can find via a mutant screen; we can expose them to radiation/ feed them radioactive food; we have a wildtype fly and each + one of the flies’wildtype cells is AA. Then we mutate it toAA , but this does not mean that every single cell will be mutated; mutagenisis occurs on a cell by cell basis; we get thousands of base pairs changed when we walk outside or are exposed to radiation in an airplane; most of the mutations that occur are a loss of function (recessive) and the wildtype function (dominant) will usually make up for these mutations c. Where do we have to start to look for changes in p
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