Download Biology 4.7 Gene Types

Genes Activity
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Aims:
Must be able to outline the various
functions of genes.
Should be able to outline how genes can be
activated and when and where.
Could be able to explain the purpose of
variations in gene activity.
Various Functions
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Genes vary due the functions they ultimately
perform.
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Genes can be:
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STRUCTURAL GENES:
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REGULATOR GENES:
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HOMEOTIC GENES:
Structural Genes
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Produce proteins that become part of the structure
and functioning of a cell or oganism.
Regulatory Genes
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Produce proteins that control the action of other
genes.
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Determine whether genes are active or not and how
fast they produce their products.
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Genes switch other genes ‘on’ and ‘off’ by producing
proteins that work in one of two ways:
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DNA bin-binding proteins binds to regions in DNA near
genes and directly switch them ‘on’ or ‘off’.
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Proteins bind to cell membrane and trigger a series of
intracellular reactions that switch gene ‘on’ or ‘off’.
Homeotic Genes (master genes)
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Control embryonic development in insects and vertebrates.
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Control the actions of hundreds of other genes.
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Important in the building of various parts of the organism at
certain times in development.
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Homeotic genes are known as HOX genes in mammals.
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HOX genes are arranged in 4 clusters:
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HOXA, 11 genes, chromosome 7
HOXB, 10 genes, chromosome 17
HOXC, 9 genes, chromosome 12
HOXD, 9 genes, chromosome 2
Mutations in HOX genes can result in profound differences in
phenotypes.
When are Genes Active
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Genes vary in their time of activity.
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Some are active for only days or weeks or
at particular ages:
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Genes for embryonic blood.
Genes for Huntington’s disease.
Some are active for the entire life:
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Those responsible for enzyme production.
Where are Genes Active
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Some genes are only active in cells of certain
tissues:
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Genes for beta haemoglobin (HBB) only active in cells
of bone marrow destined to be RBC.
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Dystrophin protein gene (DMD) only active in skeletal
muscle tissue.
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Gene for the production of growth hormone (GH) only
active in the pituitary gland.
Some genes are active in all tissues:
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Genes for enzymes involved in cellular respiration.
Identifying Active Genes
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A ‘switched on’ gene is one that is transcribing mRNA,
a ‘switched off’ gene is not producing mRNA.
MICROARRAYS is a new technology that allows
Scientists to study a large number of genes
simultaneously and:
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Identify active and inactive genes at a given time.
Compare gene expression in different cell types.
Compare genes in same cell types under different
conditions.
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Diagram p408.
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Notes on future applications of Mircoarray technology.
Activity
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Notes on ‘Switching Off Genes’
p409-411.
Biozone p197 – 206 – Recap on
DNA replication and Transcription
and Translation.