BIOL 112 Lecture Notes - Lecture 17: Frederick Griffith, Oswald Avery, Antirrhinum
15 Jun 2018
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BIOL 112: GENETICS
Having many genes and alleles determine each phenotype can lead to an infinite range of traits
Semi-Dominant Case: white and red snapdragons breed pink snapdragons (intermediate between
dom/rec. phenotype)
Allelic Series: istead of haig R ad r, ou hae r’ hih is a peretage oiatio of the doiat
allele e.g. R = 50% red piget, r = 0% red piget, r’ = 30% red piget hih egis otiuous
variation folloig Medel’s La:
- i.e. Alzheier’s; allele of Apo E allelic combinations, gradient relative to risk
- Heart attack risks are related to polygenic traits (concentrations of genes in certain regions
contribute to the risk causing variation)
o Irease the uer of gees, otiuous ariatio gets ore otiuous
Environmental contribution to phenotype (sharing): people have different environmental exposure,
which gives you a bell curve
- Penetrance: percentage of individuals of a given genotype that show the phenotype at all (e.g.
not all homozygous wrinkled peas are wrinkled)
- Expressivity: the degree to which a phenotype is expressed (e.g. shades of pink in a flower)
Contributions to Traits:
- # of traits, # of alleles in the population for each gene, environmental effects
DNA: Discovery and Replication
How to find out the chromosomes contain genetic material:
- Assay: a way of measuring, quantitating biological phenomena (e.g. respiration, photosynthesis,
memory (mice in a maze), etc.)
- Separate the cell into separate components
How to purify DNA:
- Extract lipids and proteins from the cell (e.g. phenol) & grind them up and precipitate with
ethanol
- Frederich Miescher: collected puss around a hospital, discovered DNA by grinding them
- Frederick Griffith: genetic material, live strain of bacteria to create colonies, discovered that a
chemical component from 1 cell is capable of genetically transforming another cell
o Can an extract from dead bacterial cells genetically transform living bacterial cells?
▪ There must be transforming principle that changes S bacteria to R bacteria,
whatever is transferred from dead S to live R is material that causes heredity
o Osald Aer uses Griffith’s assa to idetif the trasforig priiple to discover the
DNA had the ability to convert the R to S bacteria
DNA in Viruses: T2 bacteriophage: alien-like
find more resources at oneclass.com
find more resources at oneclass.com
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Document Summary
Having many genes and alleles determine each phenotype can lead to an infinite range of traits. Semi-dominant case: white and red snapdragons breed pink snapdragons (intermediate between dom/rec. phenotype) Heart attack risks are related to polygenic traits (concentrations of genes in certain regions contribute to the risk causing variation) I(cid:374)(cid:272)rease the (cid:374)u(cid:373)(cid:271)er of ge(cid:374)es, (cid:272)o(cid:374)ti(cid:374)uous (cid:448)ariatio(cid:374) gets (cid:373)ore (cid:862)(cid:272)o(cid:374)ti(cid:374)uous(cid:863) Environmental contribution to phenotype (sharing): people have different environmental exposure, which gives you a bell curve. Penetrance: percentage of individuals of a given genotype that show the phenotype at all (e. g. not all homozygous wrinkled peas are wrinkled) Expressivity: the degree to which a phenotype is expressed (e. g. shades of pink in a flower) # of traits, # of alleles in the population for each gene, environmental effects. How to find out the chromosomes contain genetic material: Assay: a way of measuring, quantitating biological phenomena (e. g. respiration, photosynthesis, memory (mice in a maze), etc. )
