GENE20001 Lecture Notes - Lecture 8: Arginine, Pleiotropy, Auxotrophy
A specific phenotype variation can be due to one or more genes. Various interactions can
occur between alleles/genes to produce the phenotype
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Many ways to alter gene sequence
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Not all mutations can be detected as a phenotypic change
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A gene can have many alleles in natural population (allelic series)
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Dominance relationships - gain insight into gene functions
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Concept of allelic series
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Dominance is a manifestation of how the alleles of a single gene interact in a heterozygote.
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Dominant and recessive refer to phenotype
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Dominant: only one copy of the allele is required to produce the phenotype. One or two
copies of that allele give the same phenotype.
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Haplosufficiency occurs when a diploid organism only has a single functional copy of a
gene (with the other copy inactivated by mutation) and the single functional copy
produces enough of a gene product (typically a protein) to bring about a wild-type
condition.
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Recessive allele
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Dominant allele
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Allelic interactions and dominance
8-9 Genetic interaction (dominance, complementation,
gene interaction)
Tuesday, March 18, 2014
10:10 PM
Genetics Page 1
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Haploinsufficiency occurs when a diploid organism has only a single functional copy of a
gene and the single functional copy does not produce enough of a gene product to bring
about a wild-type condition, leading to an abnormal or diseased state.
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Dominant negative = antimorphic mutation: mutant allele product acts in opposition to
normal gene activity
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The mutant product interferes with the wild type product. In this case it bends it. The
mutant product acts antagonistically
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Molecular mechanism of dominance
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Genetics Page 2
Document Summary
A specific phenotype variation can be due to one or more genes. Various interactions can occur between alleles/genes to produce the phenotype. Not all mutations can be detected as a phenotypic change. A gene can have many alleles in natural population (allelic series) Dominance relationships - gain insight into gene functions. Dominance is a manifestation of how the alleles of a single gene interact in a heterozygote. Dominant: only one copy of the allele is required to produce the phenotype. One or two copies of that allele give the same phenotype. Dominant negative = antimorphic mutation: mutant allele product acts in opposition to normal gene activity. The mutant product interferes with the wild type product. Heterozygote exhibits phenotype of both homozygotes e. g. blood groups: antigens present on rbc, 3 alleles. Phenotype of heterozygotes intermediate between the two homozygotes (on some quantitative scale of measurement)
