GENE20001 Lecture Notes - Lecture 1: Haploinsufficiency, Penetrance, Epistasis
Genetics: study of inherited variation
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Variation includes naturally occurring phenotypic variation (may be mono or polygenic) and
laboratory induced phenotypic variation (mutation)
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Phenotypic: morphological, sterile, lethal
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Molecular: biochemical (gene/gene product), DNA, protein
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Types of inherited variation:
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Mendel's First Law: Alleles will always segregate away from each other into gametes
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Mendel's second law: alleles of separate genes will always segregate independently into
gametes
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Loss of function and gain of function
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Conditional: temperature sensitive mutant
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Interactions
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Mutant alleles:
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Hypomorphic mutant
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Amorphic mutant
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Neomorphic mutant
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Gene interaction:
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1 Introduction
Thursday, 20 February 2014
10:02 PM
Genetics Page 1
Document Summary
Variation includes naturally occurring phenotypic variation (may be mono or polygenic) and laboratory induced phenotypic variation (mutation) Mendel"s first law: alleles will always segregate away from each other into gametes. Mendel"s second law: alleles of separate genes will always segregate independently into gametes. There are no rules regarding variant alleles and the phenotypes they produce. Penetrance and expressivity: if not every individual expresses phenotype then there is variable penetrance. Dominant means only one copy of the allele concerned is required to produce the phenotype. One or two copies of that allele give the same phenotype. Antimorpic mutations are dominant, act in opposition to normal gene activity. Co-dominance: heterozygote exhibits phenotype of both homozygotes. e. g. blood groups. Whether an allele shows a dominant, recessive or co-dominant phenotype may depend on which aspect of the phenotype you are looking at. At the dna sequence level all alleles are co-dominant.
