GENE FAMILY

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GENE FAMILY

• DEFINITION
• A group of functionally related gene in
  eukaryote
• Types
• 1) simple multigene
• 2) complex multigene
• 3) developmentally regulated complex multigene

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Simple multigene family

• arrowtranscription direction
• Arrangement of more than one gene repeated
  tandemly
• eg. Frog, Xenopus laevis, 5SrRNA gene

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Simple multigene family

• Genes are separated by a spacer region (sometimes
  2-6X longer than the gene)
• 5S rRNA genes are transcribed individually and
  later are processed to form the functional 5S
  rRNA molecule

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Complex multigene family

• -HISTONE GENE (Sea urchin)
• -HISTONE GENE (DROSOPHILA)
• -tRNA GENE(DROSOPHILA)

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Complex multigene family

• The complex contains a number of related genes
  separated by a spacer region
• The histone gene complex of sea urchin (5 genes
  per unit) is repeated 1000 times
• The gene is transcribed individually in the same
  direction

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Complex multigene family

• Drosophila histone genes are transcribed in both
  direction
• tRNA Drosophila tRNA gene complex contains a
  number of the same gene (3 tRNAlysgenes). These
  genes are trancribed in both direction

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Developmentally regulated complex multigene

• Genes encoding the globin subunit of hemoglobin
  (alpha beta subunits)

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ADULT
EMBRYO
FETUS
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GENE FAMILY

• developmentally regulated complex multigene
• Alpha or Beta Subunit differs in amino acid
  sequence depending on the developmental stage of
  the organism
• -Embryo 2 epsilon chains
• -Fetus gamma g (gly) dan a (ala)
• -Adult 2 beta and delta chains
• Synthesis of the subunit is programmed according
  to developmental stages

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EXON INTRON

• EXON Sequences in the mature/processed mRNA
• INTRON Sequences between exons in pre-mRNA.
  Removed after transcription (mRNA splicing)

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EXON and INTRON
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EXON and INTRON
INTRON
DNA
EXON
TRANSCRIPTION
RNA
RNA SPLICING
mRNA
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EXON and INTRON
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EXON and INTRON
branch point
branch point structure
5 splice sitedonor
lariat intermediate
3 splice siteacceptor
spliced product
intron in lariat conformation
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RNA SPLICING

• Removal of intron and ligation of exons to form
  mature mRNA
• Intron present in primary transcripts in
  eukaryote and contains many stop codons
• 50-90of pre-mRNA is intron

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EXON and INTRON
cDNA
INTRON 1
INTRON 2
Exon 1
Exon 2
Exon 3
GENOMIC DNA
RESTRICTION ENDONUCLEASE SITES
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RNA SPLICING

• intron starts with GU
• and ends with AG
• (splicing site-before GU and after AG)
• Function ?
• Variation of proteins from single pre-mRNA

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REPETITIVE DNA

• Tandem repeat (e.g. CACACACACA)
• Microsatelite 1-5 bp per unit)
• Minisatelite (lt 100 bp per unit)
• Interspersed repeat
• SINE
• LINE

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REPETITIVE DNA
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Cot½ Complexitydetermination