STRUTTURA FUNZIONE EVOLUZIONE

STRUTTURA (FUNZIONE) EVOLUZIONE

Organi, tessuti ecc.

Geni o segmenti genomici

Gene ancestrale

Duplicazione

Diversificazione

Linea di discendenza 1 (specie 1) Linea di discendenza 2 (specie 2)

Paraloghi

Paraloghi

ParaloghiOrtologhi

Ortologhi

Tempo

rDNA

I PRECURSORI DEGLI rRNA SONO PIU' LUNGHIDELLA SOMMA DEI DUE rRNA MATURI

Fig. 1. Relationships between the nucleolus, secondary constriction, NOR and ribosomal RNA genes. Typically, only a subset of the rRNA genes within a nucleolus organizer region (NOR) is active; subsequent transcription by RNA polymerase I and pre-rRNA processing causes the nucleolus to form. At metaphase, the rRNA genes that had been active during the preceding interphase give rise to a secondary constriction due to the persistent binding of transcription factors. The secondary constriction is decondensed to the point that it is generally not visible using standard light microscopy techniques. Within an NOR the tandemly arrayed rRNA genes are separated from one another by an intergenic spacer that typically contains repeated elements as well as the rRNA gene promoter, at which the transcription start site is denoted as + 1. The transcribed portion of the gene includes an external transcribed sequence (ETS) and two internal transcribed sequences, ITS1 and ITS2 that separate the 18S, 5.8S and 25S structural rRNA sequences. Multiple RNA processing events are needed to generate the structural RNAs from the primary transcript.

Maturazione dell’RNA ribosomale negli eucarioti

Tutti i genomi contengono copie multipledei geni per l’rRNA e per i tRNA

Specie

E.coli S.cerevisiae D.discoideum D.melanogaster

XY

X.laevis H.sapiens

7140 180

250 150 450 280

7140 180 165

24,000 2,000

60 250

?850

1,150 1,300

18S/28S rRNA genes

5S RNA genes

tRNA genes

tRNA

miRNA

GENI SOVRAPPOSTI (es. MHC)

GENI SOVRAPPOSTI

CLUSTER GENICI

PSEUDOGENI PROCESSATI

ARCHITETTURA DEL GENOMA

Protein coding: ca. 21,000 di cui >90% con splicing alter. De novo origin = very rare

Conserved elements: Transcription?? Conserved, Highly C., Ultra C. Enriched in regulatory elements

3.6 million constrained elements can be detected encompassing 4.2% of the genome, including a

substantial fraction of newly detected bases (blue)

Lindblad-Toh K, et al. (2011) Nature 478:476-482

Small non-coding RNA: 100 families of miRNA ca. 200 target mRNAs per ogni miRNA

Large non-coding RNA: 10% del genoma si trova sotto forma di trascritti maturi non derivati da esoni. Molti con bassi livelli di espressione. lincRNA coinvolti in cell-cycle regulation, immune response, brain processes, gametogenesis.

Mappe epigenomiche: mappatura delle porzioni funzionalmente attive.Promotori attivi: ipersensitivita’ alla DNAsi, acetilazione degli istoni, istone 3 lys-4 trimetilata.

Mappe epigenomiche: mappatura delle porzioni funzionalmente attive.Promotori attivi: ipersensitivita’ alla DNAsi, acetilazione degli istoni, istone 3 lys-4 trimetilata.

Large non-coding RNA: 10% del genoma si trova sotto forma di trascritti maturi non derivati da esoni. Molti con bassi livelli di espressione. lincRNA coinvolti in cell-cycle regulation, immune response, brain processes, gametogenesis.