Nondisjunction and chromosomal anomalies La no disyunción y las ...
By NA - uniba.it · Yonggang J, Evan E. Eichler, Stuart Schwartz, and Robert D. Nicholls Structure...
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By NA Evoluzione del genoma Lezione 22
Transcript of By NA - uniba.it · Yonggang J, Evan E. Eichler, Stuart Schwartz, and Robert D. Nicholls Structure...
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Evoluzione del genoma
Lezione 22
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Evoluzione cosa significa?Evoluzione questa sconosciuta
in italiano: processo graduale attraverso il quale qualcosa si trasforma in altra piu’ complessa e/o migliore . E’ spesso considerato sinonimo di sviluppo.
in biologia: cambiamenti nel pool genomico di una popolazione che nel corso delle generazioni, attraverso l’azione del caso e della selezione naturale portano alla nascita di nuove specie
quindi non c’e’ un tendere verso qualcosa di migliore. Questo e’ quello che ha disturbato e continua a disturbare molti.
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Quanti geni nell’uomo?
Il genoma umano
Nature Genetics 7:345 -346, 1994
Geni: 60.000 -70.000
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cosa ci dice?
2001Completamento della
sequenza del genoma umano
Il numero di geni stimato nel genoma umano ~30.000 intesi come sequenze codificanti per proteine
SNP’s:Eterozigosi media per il DNA genomico umano: ~0,0037 (0,37%). Cio’ significa che in due alleli circa 1:250-1:1000 basi sono diverse
microsatelliti: variazioni di lunghezza del DNA identificabili via PCR....
tutto finito?
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Duplicazioni di interi genomi
Nat. Genet. 31(1):100 -105 (2002)
Nat. Genet. 31(2):200 -204 (2002)
Nat. Genet. 31(2):205 -209 (2002)
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Nature, June 19, 2008
] VERTEBRATES
amphioxus
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“natural selection merely modifies,while redundancy creates”
Evolution by gene duplicationSpringer -Verlag. Berlin. 1970
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I geni Hox
GeneGeneDuplicationsDuplications(four clusters)(four clusters)
AmphioxusAmphioxus
HypotheticalHypotheticalCommonCommonAncestorAncestor
lablab pbpb DfdDfd ScrScr AntpAntp UbxUbx AbdAAbdA AbdBAbdB
DrosophilaDrosophila
(chr. 2, 7, 12, 17)
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circa 1000Geni per i recettori olfattivi
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more enzyme activity(amylase)
Destino dei geni duplicati
Duplication 1 loss
nonfunctional D
uplic
atio
n2
neofunction
sub
func
tiona
lizat
ion
1 2 3
3
1 2
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I geni delle globinePNAS 105:1590 -5, 2008
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“natural selection merely modifies,while redundancy creates”
Evolution by gene duplicationSpringer -Verlag. Berlin. 1970
Nat Genet 39:1256-1260 (2007)
Present in the salivaStarch digestion in the mouth
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Hadza women(Tanzania)
gathering tuberous
Yakut horseman(Siberia)
after hunting
Starch consumption is a prominent characteristic of agricultural societies
Rainforest and circum -arctic hunter-gatherers and some pastoralists consume much less starch.
high
low
~5
~7
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plasticity=
variability=
evolution
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perfezione=
nessuna prospettivaevolutiva
~ il 98% delle specie che sono
esistite sulla terrasi sono estinte
Lactase-phlorizin hydrolase (LPH) enzymehydrolyzes lactose into glucose and galactose
LPH declines rapidly after weaning.
However, some individuals maintain the ability to digest milk and other dairy products into adulthood.
Lactase persistency
Beja -Pereira et al. 2003 Early Neolithic cattle pastoralist
Lactase gene
3,9 kb iinsertion ( del) in the first intron
In Africans: 0.86% (0.11%)In Europeans: 0.11% (0.86%)
linkage disequilibrium
lactase persistence
in complete with
the single-nucleotide polymorphism that has been associated with
1920
1st intron
Nat Genet 2007, 39:31 -40
1271
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SD (in om ozigosi)
CNV
Assenza di datiper questioni tecniche
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DNA da testare
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DNA da testare
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comuni: 66% (79.8Mb)
comparazione uomo-scimpanze'
- umano-specifiche: 33% (26.5Mb)
- scimpanze'-specifiche (11.4Mb)
Duplicazioni segmentali
-
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Nature 453:56-64 (2008).
Nature 444:444-454 (2006).
Differenza media fra 2 individui: circa 20.000.000 bp
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Il significato?
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plasticity=
variability=
evolution
perfezione=
nessuna prospettivaevolutiva
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fixed CNV (SD)
CNV
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fixed CNV (SD)
CNV
after meiosis
before checkpoint
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… Finally, the high level of instability at the alpha-globin locus contrasts with the rarity in most populations of chromosomes carrying duplications or deletions, pointing to strong selective constraints that maintain alpha-globin gene copy number in human populations.
104:10950 -5 (2007).PNAS
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Li-Fraumeni syndrome is an autosomal dominantly inherited disorder characterized by a strikingly increased risk of early-onset breast cancer, sarcomas, brain tumors and other neoplasms in individuals harboring germline
mutations.
PNAS
TP53
in press
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Science 320: 539 -543, 2008
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Am J Hum Genet 81: 1057-1069, 2007
Nature Genet 40:1076-1083, 2008.
Yonggang J, Evan E. Eichler, Stuart Schwartz, and Robert D. NichollsStructure of Chromosomal Duplicons and their Role in Mediating Human Genomic DisordersGenome Research Vol. 10, Issue 5, 597 -610, May 2000
Analysis of long stretches of available sequence from human chromosomes 22 and X suggest that 5% -10% of the genome may be duplicated (Mazzarella and Schlessinger 1998; Dunham et al. 1999). Sequence homology between duplicated DNA segments provides a chance for misalignment during meiosis, leading to unequal exchange and chromosome rearrangement, by either inter - or intrachromosomal or sister chromatid homologous recombination.This process with divergence between duplicated segments is essential to the generation of diversity and new genes over evolutionary time, although the more typical, short-term effect is genetic disease.
Genome Research 2000
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Variabilita’ ricchezza per la specie
Variabilita’ problemi per i singoli
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E’ la logica :le esigenze dei m olti contano di piu’ di quelle dei pochi o di uno
Mr.Spock: Star Trek : L’ira di Khan
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