David%20Sadava%20%20H.%20Craig%20Heller%20Gordon%20H.%20Orians%20William%20K.%20Purves%20%20David%20M.%20Hillis%20%20Biologia.blu%20B%20

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David Sadava H. Craig Heller Gordon H. Orians
William K. Purves David M. Hillis
Biologia.bluB Le basi molecolari della vita
e dellevoluzioneThe Eukaryotic Genome and Its
Expression
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The Eukaryotic Genome and Its Expression

• What are the characteristics of the eukaryotic
  genome?
• How are eukaryotic gene transcripts processed?
• How is eukaryotic gene transcription regulated?

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The Eukaryotic Genome and Its Expression - What
are the characteristics of the eukaryotic
genome? ?

• Key differences between eukaryotic and
  prokaryotic genomes
• eukaryotic genomes are larger
• eukaryotic genomes have more regulatory
  sequences
• much of eukaryotic DNA is non-coding.

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The Eukaryotic Genome and Its Expression - What
are the characteristics of the eukaryotic
genome? ?
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The Eukaryotic Genome and Its Expression - What
are the characteristics of the eukaryotic
genome? ?

• Eukaryotes have multiple chromosomes.
• In eukaryotes, translation and transcription are
  physically separated which allows many points of
  regulation before translation begins.

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The Eukaryotic Genome and Its Expression - What
are the characteristics of the eukaryotic
genome? ?

• Eukaryote model organisms
• yeast, Saccharomyces cerevisiae
• nematode (roundworm), Caenorhabditis elegans
• fruit fly, Drosophila melanogaster
• thale cress, Arabidopsis thaliana.

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The Eukaryotic Genome and Its Expression - What
are the characteristics of the eukaryotic genome?
Eukaryotic mRNA is transcribed in the nucleus but
translated in the cytoplasm
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The Eukaryotic Genome and Its Expression - What
are the characteristics of the eukaryotic
genome? ?

• Eukaryote genomes have two types of highly
  repetitive sequences that do not code for
  proteins
• minisatellites 1040 bp, repeated several
  thousand times. Number of copies varies among
  individualsprovides molecular markers
• microsatellites 13 bp, 15100 copies.

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The Eukaryotic Genome and Its Expression - What
are the characteristics of the eukaryotic
genome? ?

• Other moderately repetitive sequences can move
  from place to place in the genome - transposons.
• Transposons make up 40 percent of human genome,
  only 310 percent in other sequenced eukaryotes.

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The Eukaryotic Genome and Its Expression - What
are the characteristics of the eukaryotic genome?
DNA transposons and transposition
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The Eukaryotic Genome and Its Expression - What
are the characteristics of the eukaryotic
genome? ?

• The function of the transposons is unclear. They
  may be cellular parasites.
• If a transposon is inserted into a coding region,
  a mutation results. If its in a somatic cell,
  cancer can result.
• Transposons can carry genes to new
  locationsadding to genetic variation.
• Transposons may have played a role in
  endosymbiosis genes from the once-independent
  prokaryotes may have moved to the nucleus by DNA
  transposons.

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The Eukaryotic Genome and Its Expression - What
are the characteristics of the eukaryotic genome?
Transcription of an eukaryotic gene (part 1)
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The Eukaryotic Genome and Its Expression - What
are the characteristics of the eukaryotic
genome?
Transcription of an eukaryotic gene (part 2)
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The Eukaryotic Genome and Its Expression - What
are the characteristics of the eukaryotic
genome? ?

• Protein-coding genes have noncoding
  sequencesintrons.
• The coding sequences are extrons.
• Transcripts of introns appear in the pre-mRNA,
  they are removed from the final mRNA.

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The Eukaryotic Genome and Its Expression - How
are eukaryotic gene transcripts processed?

• RNA splicing removes introns and splices exons
  together.
• Pre-mRNA is bound by small nuclear
  ribonucleoprotein particles (snRNPs).
• Consensus sequences are short sequences between
  exons and introns. snRNP binds here, and also
  near the 3' end of the intron.

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The Eukaryotic Genome and Its Expression - How
are eukaryotic gene transcripts processed?

• With energy from ATP, proteins are added to form
  an RNA-protein complex, the spliceosome.
• The complex cuts pre-mRNA, releases introns, and
  splices exons together.

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The Eukaryotic Genome and Its Expression - How
are eukaryotic gene transcripts processed?
The spliceosome
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The Eukaryotic Genome and Its Expression - How
are eukaryotic gene transcripts processed?

• During development, different globin genes are
  expressed at different times differential gene
  expression.
• ?-globin is in hemoglobin of human fetusit binds
  oxygen more tightly than adult hemoglobin.

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The Eukaryotic Genome and Its Expression - How
are eukaryotic gene transcripts processed?
Differential expression in the globin gene family
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The Eukaryotic Genome and Its Expression - How
are eukaryotic gene transcripts processed?

• Some gene families have pseudogenesfrom a
  mutation that results in loss of function.
• Pseudogenes may lack a promoter, or recognition
  sites for removal of introns.
• They are designated by ? (psi).
• Expression of genes must be precisely regulated
  during development.
• Gene expression can be regulated at several
  points in the transcription and translation
  processes.

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The Eukaryotic Genome and Its Expression How is
the eukaryotic gene transcription regulated? ?
Potential points for the regulation of gene
expression (part 1)
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The Eukaryotic Genome and Its Expression How is
the eukaryotic gene transcription regulated?
Potential points for the regulation of gene
expression (part 2)
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The Eukaryotic Genome and Its Expression How is
the eukaryotic gene transcription regulated?
Potential points for the regulation of gene
expression (part 3)
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The Eukaryotic Genome and Its Expression How is
the eukaryotic gene transcription regulated?
Local remodeling of chromatin for transcription
(part 1)
Proteasome Breaks Down Proteins
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The Eukaryotic Genome and Its Expression How is
the eukaryotic gene transcription regulated?
Local remodeling of chromatin for transcription
(part 2)
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The Eukaryotic Genome and Its Expression How is
the eukaryotic gene transcription regulated?
Transcription factors, regulators, and activators
(part 1)
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The Eukaryotic Genome and Its Expression How is
the eukaryotic gene transcription regulated?
Transcription factors, regulators, and activators
(part 2)
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The Eukaryotic Genome and Its Expression How is
the eukaryotic gene transcription regulated?
Coordinating gene expression (part 1)
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The Eukaryotic Genome and Its Expression How is
the eukaryotic gene transcription regulated?
Coordinating gene expression (part 2)
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The Eukaryotic Genome and Its Expression How is
the eukaryotic gene transcription regulated?
Transcription from multiple genes for rRNA
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The Eukaryotic Genome and Its Expression How is
the eukaryotic gene transcription regulated?
Alternative splicing results in different mature
mRNAs and proteins
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The Eukaryotic Genome and Its Expression How is
the eukaryotic gene transcription regulated?
Proteasome breaks down proteins