Pleiotropy: Difference between revisions
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Pleiotropy is the manifestation of several </span>[[Phenotype|traits]]<span style="line-height: 1.5em; font-size: 13px;"> present in an </span>[[Organism|organism]]<span style="line-height: 1.5em; font-size: 13px;">, which are caused by a single </span>[[Gene]] | Pleiotropy is the manifestation of several </span>[[Phenotype|traits]]<span style="line-height: 1.5em; font-size: 13px;"> present in an </span>[[Organism|organism]]<span style="line-height: 1.5em; font-size: 13px;">, which are caused by a single </span>[[Gene]]<ref>http://www.nature.com/scitable/topicpage/pleiotropy-one-gene-can-affect-multiple-traits-569</ref>. | ||
The outcome of these [[Genetic crosses|crosses]] stray from the normal [[Mendelian inheritance|Mendelian]] | The outcome of these [[Genetic crosses|crosses]] stray from the normal [[Mendelian inheritance|Mendelian]] ratios. This is due to lethal [[Alleles|alleles]] resulting in some [[Genetic crosses|crosses]] producing a lethal [[Genotype|genotype]]. An example of this is known in Manx cats. Manx cats carry a [[Dominant allele|Dominant]] mutation which affects spinal formation in cats. This leads to the tail of the cat being shorter, or not developing at all. The ratio of [[Genotype|genotypes]] produced when two Manx cats are crossed is 2:1, this is not the expected [[Mendelian inheritance|Mendelian]] ratio of 3:1. This is because the [[Homozygous|homozygous]] [[Dominant allele|dominant]] [[Genotype|genotype]] is lethal, meaning the embryo does not develop. The [[Phenotype|phenotypic]] ratio produced is therefore 1 normal: 2 Manx <ref>Reference to the book: Genetics: Analysis and Principles, Robert J. Brooker, Granite hill publishers 2009.</ref>. | ||
Further examples of pleiotropy can be seen in cats with white fur and blue eyes, the dominant white allele (W) is [[Epistasis|epistatic]] to all other coat colour genes, resulting in this [[Phenotype|phenotype]]. The mutant allele, W blocks the production of [[Melanin|melanin]] through [[Melanocytes|melanocytes]]<ref>IB.Berkeley Education (2014) Basic Genetics as revealed by cats. Available at: http://webcache.googleusercontent.com/search?q=cache:5hGXKb8NGc8J:ib.berkeley.edu/courses/ib162/Week3a.htm (26.11.14)</ref> . In 40% of cases this pattern of pigmentation is associated with deafness, believed to result from the migration of pigment cells to various tissues, including the middle ear- where functionality is essential for hearing <ref name="null">Hartl D., Ruvolo M., (2012) Genetics, 8th Edition, USA: Jones and; Barlett Learning</ref>. The [[Cochlea|cochlea]] of the ear contains a band of melanocytes that regulate ion balance, if this balance is interrupted signal transmission to the brain degenerates and irreversible deafness results<ref>IB.Berkeley Education (2014) Basic Genetics as revealed by cats. Available at: http://webcache.googleusercontent.com/search?q=cache:5hGXKb8NGc8J:ib.berkeley.edu/courses/ib162/Week3a.htmk (26.11.14)</ref>.Defective pigments, therefore, lead to deafness and thus deafness is considered a pleiotropic effect of white coat and blue eye colour - the dominant white [[Locus|locus]] exhibits pleiotropy, affecting both coat colour and hearing<ref>Hartl D., Ruvolo M., (2012) Genetics, 8th Edition, USA: Jones and Barlett Learning</ref>. | |||
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Latest revision as of 17:28, 4 December 2017
Pleiotropy is the manifestation of several </span>traits present in an organism, which are caused by a single Gene[1].
The outcome of these crosses stray from the normal Mendelian ratios. This is due to lethal alleles resulting in some crosses producing a lethal genotype. An example of this is known in Manx cats. Manx cats carry a Dominant mutation which affects spinal formation in cats. This leads to the tail of the cat being shorter, or not developing at all. The ratio of genotypes produced when two Manx cats are crossed is 2:1, this is not the expected Mendelian ratio of 3:1. This is because the homozygous dominant genotype is lethal, meaning the embryo does not develop. The phenotypic ratio produced is therefore 1 normal: 2 Manx [2].
Further examples of pleiotropy can be seen in cats with white fur and blue eyes, the dominant white allele (W) is epistatic to all other coat colour genes, resulting in this phenotype. The mutant allele, W blocks the production of melanin through melanocytes[3] . In 40% of cases this pattern of pigmentation is associated with deafness, believed to result from the migration of pigment cells to various tissues, including the middle ear- where functionality is essential for hearing [4]. The cochlea of the ear contains a band of melanocytes that regulate ion balance, if this balance is interrupted signal transmission to the brain degenerates and irreversible deafness results[5].Defective pigments, therefore, lead to deafness and thus deafness is considered a pleiotropic effect of white coat and blue eye colour - the dominant white locus exhibits pleiotropy, affecting both coat colour and hearing[6].
References:
- ↑ http://www.nature.com/scitable/topicpage/pleiotropy-one-gene-can-affect-multiple-traits-569
- ↑ Reference to the book: Genetics: Analysis and Principles, Robert J. Brooker, Granite hill publishers 2009.
- ↑ IB.Berkeley Education (2014) Basic Genetics as revealed by cats. Available at: http://webcache.googleusercontent.com/search?q=cache:5hGXKb8NGc8J:ib.berkeley.edu/courses/ib162/Week3a.htm (26.11.14)
- ↑ Hartl D., Ruvolo M., (2012) Genetics, 8th Edition, USA: Jones and; Barlett Learning
- ↑ IB.Berkeley Education (2014) Basic Genetics as revealed by cats. Available at: http://webcache.googleusercontent.com/search?q=cache:5hGXKb8NGc8J:ib.berkeley.edu/courses/ib162/Week3a.htmk (26.11.14)
- ↑ Hartl D., Ruvolo M., (2012) Genetics, 8th Edition, USA: Jones and Barlett Learning