Deviations of Mendelian inheritance
- Created by: kpritchard16
- Created on: 26-05-18 16:39
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- Deviations from Mendelian inheritance
- Lethal alleles
- conditional lethal alleles
- may kill an organism only when certain environmental conditions prevail
- One that has the potential to cause the death of an organism, result of mutation in essential genes, usually recessive
- conditional lethal alleles
- Sex-influenced traits
- traits where on allele is dominant in one sex but recessive in the opposite sex
- Baldness in humans
- traits where on allele is dominant in one sex but recessive in the opposite sex
- Sex-limited traits
- traits that only occur in one of the two sexes, determined by sex hormone levels
- Breast development (females), beard development (males)
- traits that only occur in one of the two sexes, determined by sex hormone levels
- Multiple alleles
- the presence of more than two alleles of a gene in a population
- PKU, CF
- the presence of more than two alleles of a gene in a population
- Incomplete dominance
- the heterozygote has a phenotype that is intermediate between the corresponding homozygote phenotypes
- Co-dominance
- the presence of both alleles in heterozygous genotypes can be detected, has own phenotype
- Over- dominance
- heterozygote is fitter than both of the corresponding homozygotes
- Sickle cell anaemia
- heterozygote is fitter than both of the corresponding homozygotes
- Under-dominance
- heterozygote is less fit than either of the homozygotes
- Epistasis
- Recessive
- homozygous recessive at one locus(w) prevents the other locus(m) from exerting its phenotype
- phenotype of wwmm = wwMm
- 9:3:4
- homozygous recessive at one locus(w) prevents the other locus(m) from exerting its phenotype
- Dominant
- dominant allele at one locus(B) prevents the other locus(A) from exhibiting homozygous recessive phenotype
- phenotype A_B_ = aaB_
- 12:3:1
- dominant allele at one locus(B) prevents the other locus(A) from exhibiting homozygous recessive phenotype
- Dominant and Recessive
- dominant allele at one locus(A) produces the same phenotype as homozygous recessive at other locus(B)
- phenotype A_BB=A_Bb=A_bb
- 13:3
- dominant allele at one locus(A) produces the same phenotype as homozygous recessive at other locus(B)
- Duplicate recessive
- complete dominance at both loci
- phenotype A_bb=aaB_=aaB_ , A_B_ is different
- 9:7
- complete dominance at both loci
- Duplicate dominant
- presence of dominant allele at either loci produces dominant phenotype
- phenotype A_B_=A_bb=aaB_ , aabb is different
- 15:1
- presence of dominant allele at either loci produces dominant phenotype
- Duplicate gene with cumulative effects
- dominant allele at either locus, both not both, produces same phenotype
- phenotype A_bb=aaB_ , aabb distinct
- 9:6:1
- dominant allele at either locus, both not both, produces same phenotype
- when one gene masks and effects the phenotype of another
- gene that does this is called a modifier or epistasis gene
- Recessive
- Penetrance
- whether a genotype is expressed as phenotype
- proportion of organisms whose phenotype matches genotype for given character is penetrance of genotype
- always expressed = completely penetrant
- not always expressed = incompletely penetrant
- whether a genotype is expressed as phenotype
- Expressivity
- genes that are expressed to different degrees in different organisms, variable expressivity
- Polydactyly
- Pleiotrophy
- single-gene disorder with many symptoms, or gene that controls several functions or has more than one effect
- porphyria
- single-gene disorder with many symptoms, or gene that controls several functions or has more than one effect
- Heterogeneity
- Genetic
- different genes that produce the same phenotype
- 132 separate genes control hearing loss
- different genes that produce the same phenotype
- Allelic
- multiple alleles at same gene locus
- 1600 allele mutations in CFTR that cause CF
- multiple alleles at same gene locus
- Genetic
- Phenocopies
- environmental caused trait that appears to be inherited is phenocopy
- Siamese cats
- environmental caused trait that appears to be inherited is phenocopy
- Lethal alleles
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