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moving target definition of gene:
gene = nucleotide coding sequence for a particular prot, molecular component (or a larger complex) or trait

DNA studied hard in 20th century
gene is THE unifying concept in sci
smallest unit of biological instruction
genes full of "junk", introns, intervening sequences

CF gene CFTR cycstic fibrosis transmembrane conductance regulator, 250kb stretch of DNA on xsome 7
xsome 11 has gene for Beta Globin

Duchenne-type Muscular Dystrophy
largest gene known
2.3 million base pairs
1.5% of xsome where fuond
has 70 exons or more

HUMAN GENOME PROJECT
began 1985, many labs, originally funded by US Dept of Energy
they wanted to look for radiation damage
completed 2005 by private corp
human genome is *25,000 genes (debatable)(fruit fly drosophilia has 13,600)
99% noncoding
sonic hedgehog = gene for organogenesis
*proteomics = what do proteins do? how genes are expressed, many more possibilities than genes
each gene has a *locus on an xsome
variants of genes are *alleles
sig allelic variation = *polymorphisms
genes that don't vary much are highly *conserved
change in gene is a *mutation
*wild-type allele is described as common or normal type





WELL KNOWN GENES
there is no conventional naming system
BRCA1
p53
c-myc

CAUSES OF MUTATIONS
radiation: esp cosmic rays, radioactive decay, xrays
(known since 1927 that xrays are mutagenic, Hermann Muller)
chemicals: esp polycyclic aromatic hydrocarbons, oxidative agents
methylators (methylene chloride is v dangerous) and alkylators (in paints & strippers)
1941 Charlotte Auerbach showed mustard gas is mutagenic
list of chems that are known mutagens is over 1000 now
not sure about phenol used in cadaver lab, is active ingrednt in chloraseptic lozenges/sore throat

TAUTOMERIC SHIFT
reversible shift of H atom location, changing isomer-->diff bonding
"tautomeric shifts that modify the pairing of nucleotides can result in base substitutions and, as a result, mutations"
happens with thymine, guanine, cytosine and adenine-->base pair substitutions, mutations
enol form of thymine bonds to keto form of guanine
thymine, guanine normally keto:
when enol (rare) forms 3 H bonds with ketos of guanine or thymine, respectively
cytosine and adenine normally in amino forms
when in the rare imino forms they can join by two hydrogen bonds with amino forms of adenine or cytosine, respectively
http://www.jrank.org/health/pages/20548/tautomeric-shift.html

TWO TYPES OF GENES
structural genes-->can't build something, usu dominant mutations, collagen, elastin, fibrillin,
actin, spectrin abnormalities
metabolic genes-->inborn errors of metabolism, precursors accumulate, deficiency of product, possible activation of alternative pathway

COMMON PHENOTYPES OF METABOLIC DZ
failure to thrive
gradual onset (variable)
unusual dietary response (to metabolite that can't be metabolized)
mental retardation
dysmorphology

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