Organização gênica de eucariotos

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Rachel Valente Neves
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1 Universidade Estadual de Maringá Organização gênica de eucariotos Disciplina: Biologia Molecular Turmas 1/ Profa. Dra Maria Aparecida Fernandez

2 Estrutura e expressão de gene eucariótico

3 Transcrição de mrnas e outros RNAs em um domínio complexo PARLR: RNA longo associado ao promotor ASRs: RNAs anti senso PASRs: RNA curto associado ao promotor mirna: micro-rna de sequencia intronica com estrutura secundária TASRs: RNA curto associado ao terminador

4 Tamanho dos genomas

5 Replicons na estrutura do genoma de eucariotos

7 Múltiplos mrnas do gene humano EPB41 Éxons em rosa e não codificadoras 5 e 3 em cinza

8 Proporção de genes de cópia única, família de genes e pseudogenes no genoma humano

11 Sequencias genicas e intergenicas no genoma humano

12 Genoma mitocondrial humano

13 Paradoxo do valor C A quantidade de DNA em uma célula haplóide de um organismo não está relacionada com a complexidade evolucionária ou número de genes

14 O tamanho do genoma não está relacionado com o número de genes e nem com a complexidade aparente de um organismo Closely related organisms can have genome sizes that vary by 100x Human genome is 30x smaller than some plant genomes

15 Os genomas dessas espécies relacionadas tem a mesma quantidade de DNA mas diferem no número de cromossomos

16 Eucaryote Chromosome Numbers Organism Common Diploid Chromosome Name Number Myrmecia pilosula Ant 2 Felis catus Cat 38 Homo sapiens Human 46 Canis familiaris Dog 78 Ophioglossum reticulatum Fern 1260

17 (G Paradox)

18 How Many Genes in the Human Genome? (G Paradox) Current estimate is 30,000-40,000 Drosophila (fruitfly) has ~13,000 genes C. elegans (nematode worm) has ~20,000 genes Mouse has ~30,000 genes Human gene transcripts (mrna) commonly undergo alternative splicing More human genes are transcription factors which interact with larger number of control elements Exon DNA pre-mrna Translated into 3 proteins Transcription Splicing mrna 1 Intron mrna 2 mrna 3

19 There are different classes of eukaryotic DNA based on sequence complexity. Coding sequences less than 5% of the genome!

20 Genes de cópia única

21 Sequencias repetidas representam 50% ou mais em um genoma

22 Genome size (bp) Proportions of Repetitive and Nonrepetitive DNA Nonrepetitive DNA Repetitive DNA

23 Human Genome Organization HUMAN GENOME Nuclear genome 3000 Mb ~30% genes? ~70% Genes and generelated sequences Unique or moderately repetitive ~10% ~90% Coding DNA Noncoding DNA Extragenic DNA Two rrna genes Mitochondrial genome 16.6 kb 37 genes 22 trna 13 polypeptideencoding genes genes 80% 20% Unique or low copy number Moderate to highly repetitive Pseudogenes Gene fragments Introns, untranslated sequences, etc. Tandemly repeated or clustered repeats Interspersed repeats

24 Repetitive DNA Moderately repeated DNA Tandemly repeated rrna, trna and histone genes (gene products needed in high amounts) Large duplicated gene families Mobile DNA Simple-sequence DNA Tandemly repeated short sequences Found in centromeres and telomeres (and others) Used in DNA fingerprinting to identify individuals

25 Simple sequence repeats Tamdem repeats of a particular k-mer 1 13 base repeat unit microsatellite Trinucleotide repeats repeats minisatellites variable numbers of tandem repeats 3% of genome Used in mapping

26 Simple sequence repeats

27 Distribution of sequence types in the human genome

28 Long Interspersed Nuclear Elements (LINEs) Characteristics 60 bp - 7 kb Considerable variation in length due to 5 truncations, deletions, and rearrangements ~500,000 elements/haploid genome (15-20%) 3-4,000 are full-length 1-2% capable of transposition, probably via an RNA intermediate (as with retroviruses) Distribution Found in A-T rich regions 5 3 ORF2 ORF1 A-T rich

29 Short Interspersed Repetitive Elements (SINEs): Alu Elements Characteristics Consensus: 281 nt Consists of two related units Considerable variation in length due to deletions, substitutions, or insertions ~1,000,000 elements/haploid genome (~12%) Distribution Average spacing is 4-kb apart Scattered but non-random? Deleterious when inserted within a gene Examples of insertions which assist in transcription regulation when inserted in control region of a gene 1 GGCCGGGCGC GGTGGCTCAC GCCTGTAATC CCAGCACTTT 41 GGGAGGCCGA GGCGGGCGGA TCACGAGGTC AGGAGATCGA 81 GACCATCCCG GCTAAAACGG TGAAACCCCG TCTCTACTAA 121 AAATACAAAA AATTAGCCGG GCGTAGTGGC GGGCGCCTGT 161 AGTCCCAGCT ACTTGGGAGG CTGAGGCAGG AGAATGGCGT 201 GAACCCGGGA GGCGGAGCTT GCAGTGAGCC GAGATCCCGC Selfish DNA? 241 CACTGCACTC CAGCCTGGGC GACAGAGCGA GACTCCGTCT 281 C

30 Gene families E.g. globins, actin, myosin Clustered or dispersed Pseudogenes

31 Pseudogenes Nonfunctional copies of genes Formed by duplication of ancestral gene, or reverse transcription (and integration) Not expressed due to mutations that produce a stop codon (nonsense or frameshift) or prevent mrna processing, or due to lack of regulatory sequences

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