BIOL 2131 Lecture Notes - Lecture 5: Cysteine, Amylase, Wild Type
16 May 2013
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Genes)code)for)proteins)(ch2):: see+figure+2. 1+!+very+important+figure, a+chromosome+contains+a+very+long+stretch+ of+dna+that+contains+many+genes, genes+were+initially+thought+to+be+a+light+switch+ (on/off),+but+now+they"re+thought+to+be+a+dimmer+ switch+(on/off+and+in+between), most+genes+in+the+genome+code+for+proteins, functional+significance+to+the+evolution+of, for+every+single+gene+that"s+at+a+specific+ the+organism+ a+single+gene)+ located+(locus+generally+doesn"t+change)+ locus,+there+are+alternate+forms+of+that+gene+ !+alleles: alleles:+alternate+forms+of+a+gene+(may+be+many+for, for+genes+that+are+conservative+(critical+function) , locus:+region+on+the+chromosome+where+a+gene+is, for+example,+hemoglobin+gene+is+always+on+the+ exact+same+spot+of+the+chromosome+for+everybody+, genes+on+a+specific+chromosome+are+said+to+be+ linked+o they+do+not+assort+independently+during+ meiosis+as+do+genes+that+are+on+different+ chromosomes, recombination+can+occur+between+homologous+chromosomes+during+meiosis, the+locus+(location+of+those+genes)+stays+the+same,+but+you+may+be+changing+the+ (crossing+over), causes+genetic+variation+ sister+chromatids+back+and+forth+ Discovery)of)2006:)cnvs) new+discovery:+ (descendants+from+europe,+africa,+asia): you+get+one+maternal+and+one+paternal+copy+for+each+gene+(mendel), however,+in+2006+(after+the+human+genome+was+sequenced+in+2003),+there+was+a, global+variation+in+copy+number+in+the+human+genome + +title+of+paper, compared+genome+sequences+from+270+people+from+4+populations, they+compared+the+chromosomal+sequences, they+chose+these+regions+to+look+at+variations+of+dna+sequences,+because, did+this+on+somatic+cells, 1447+cnvs+account+for+~12%+of+genome+(total+of+360+megabases), cnvs:+copy+number+variations+(>+1000+bp)+ human+evolution+came+from+these+areas+ Individual+3+could+have+2+cnv+for+maternal+and+0+for+paternal: this+wouldn"t+be+a+big+deal+if+cnvs+didn"t+contain+genes,+but+it+could+be+a, what"s+worse,+individual+2+or+3?+either+one+because+in+individual+2,+you+have+ drastic+change+if+they+do+ more+than+one+copy+of+the+gene+and+you+have+over+(4+copies+ instead+of+2). +in+individual+3,+you+have+nothing+from+father+so+under$ expression+(1+copy+instead+of+2). , what+does+this+mean?, for+some+genes,+we+may+inherit+more+or+less+genes+from+one+parent+ (genomic+copy+number)+ Pmp22 gene copy number and impact on disease. Chareotamarieatooth)(cmt))disease:: most+common+nerve+related+disorder, myelin+sheath+damage+in+peripheral+nerves, diagnosed+in+mid+and+progressively, caused+by+mutation+in+pmp22+gene+(peripheral, there+are+mutations+in+pmp22+that+cause+ gets+worse+ Myelin+protein)+ phenotypes+ severe+form+of+disease. +there+could+also+be+no+ mutation+in+pmp22,+but+the+child+still+has+the+ disease. +how?+you+have+more+or+less+than+2+ copies+of+genes+!+cnv: another+43+genes+are+involved+in+other+cmt, see+figure+!+gene+dosage+affects+symptoms, pmp22+gene:+copy+number+and+impact, numerous+possibilities:+the+number+of+ extra,+missing,+and+mutated+(red)+pp22+ genes+leads+to+neuropathies+of+varying+ severity+(cmt1a+and+hnpp)+ on+disease, 2+copies+!+normal, 3+copies+(2+from+mom,+1+from+dad)+!+cmt1a,+mild+form, 1+copy+(1+from+mom,+0+from+dad)+!+hnpp,+worse+form, 4+copies+(2+from+mom,+2+from+dad)+!+severe+cmt1a, 3+copies+(2+from+mom+but+one+mutated,+1+from+dad)+!+mild+cmt1a,+hnpp+ features+ Multicopy+genes +paper. +they+discovered+one+could+ have+48+copies+of+a+gene!+: copy+number+variation+for+specific+genes+vary, asian+=+red,+european+=+green,+african+=+blue, don"t+need+to+memorize+names+of+genes,+just+ general+trends, kiaa1267+gene:+ Human)evolution)and)copy)number)variation:) number: can+this+copy+number+variation+theory+also+explain+some+human+phenotypes?, diet+(high+vs. +low+starch)+can+select+for+high+amylase+gene+(amy1)+copy+ numbers+of+that+amy1+gene+than+those+that+had+low+starch+diet+(africa), focus+on+diets+because+they"re+significantly+different+between+populations, they+found+that+high+starch+diet+individuals+(asia+and+europe)+had+more+copy, thus,+high+starch+diets+=+high+amylase+copy+number, so+the+amy1+gene+is+under+very+strong+selective+pressure, you+need+more+than+2+copies+of+amy1+genes+to+survive, key+words+of+evolution:+eat,+survive,+reproduce+ It"s+a+sequence+of+dna+that+encodes+a+functional+rna+molecule;+in+protein+ coding+genes,+the+rna+in+turn+codes+for+protein. : an+alternate+form+of+a+gene+(not+an+exact+copy!!, large+number+of+variation+in+the+dna+of+a+genome+that+results+in+the+cell, what+is+an+snp?+ having+an+abnormal+copies+of+one+or+more+sections+of+the+dna+(either+more+ or+less+than+the+regular+2+copies)+ but+10%+has+a+rather+than+c+at+a+single+spot, can+or+cannot+have+genes+within+those+regions, single+number+polymorphisms+!+example:+90%+of+class+has+same+genome,, there+are+millions+of+snps+all+the+way+through+our+genome+when+you, 23+and+me+company+sequences+snps, looking+at+chromosome+15+for+maternal+and+paternal+ compare+individuals, see+figure:+*very)important)on)midterm*+ It+was+believed+that+a+gene+encodes+an+enzyme+ proteins!! encodes+a+functional+rna+molecule+(2013)+ that+were+defective+in+an+enzyme+involved+in+a+ pathway: we+know+now+that+this+hypothesis+is+not+true+, some+enzymes+are+produced+by+>+1+gene, one+gene+=+single+polypeptide +hypothesis+(1962), some+genes+only+encode+rna+!+not+all+genes+encode, definition+of+gene:+gene+is+a+sequence+of+dna+that, most+mutations+that+affect+gene+function+are+recessive, see+figure+2. 2:+ (where+get+absence+or+reduction+in+protein+function), wild+type+homozygote+=+wild+type,+wild+type+
