A hereditary carrier (genetic carrier or just carrier), is a person or other organism that has inherited a recessive allele for a genetic trait or mutation but usually does not display that trait or show symptoms of the disease. Carriers are, however, able to pass the allele onto their offspring, who may then express the genetic trait.
Punnett square: If the other parent does not have the recessive genetic disposition, it does not appear in the phenotype of the children, but on the average 50% of them become carriers.
Carriers in autosomal inheritancesedit
Punnett square: If both parents are carriers, on the average 25 % of the offspring have the recessive trait in phenotype and 50 % are carriers.
Autosomal dominant-recessive inheritance is made possible by the fact that the individuals of most species (including all higher animals and plants) have two alleles of most hereditary predispositions because the chromosomes in the cell nucleus are usually present in pairs (diploid). Carriers can be female or male as the autosomes are homologous independently from the sex.
In carriers the expression of a certain characteristic is recessive. The individual has both a genetic predisposition for the dominant trait and a genetic predisposition for the recessive trait, and the dominant expression prevails in the phenotype. In an individual which is heterozygous regarding a certain allele, it is not externally recognisable that it also has the recessive allele. But if the carrier has a child, the recessive trait appears in the phenotype, in case the descendant receives the recessive allele from both parents and therefore does not possess the dominant allele that would cover the recessive trait. According to Mendelian Law of Segregation of genes an average of 25% of the offspring become homozygous and express the recessive trait. Carriers can either pass on normal autosomal recessive hereditary traits or an autosomal recessive hereditary disease.
Carriers in gonosomal inheritancesedit
The mother is a carrier of the recessive hereditary disposition for Color blindness. The Y chromosome of the father cannot oppose this. The healthy allele on the X chromosome of the father can compensate for this in a daughter. She can see normally, but she becomes a conductor. The same pattern of inheritance applies to Haemophilia.
Gonosomal recessive genes are also passed on by carriers. The term is used in human genetics in cases of hereditary traits in which the observed trait lies on the female sex chromosome, the X chromosome. The carriers are always women. Men cannot be carriers because they only have one X chromosome. The Y chromosome is not a really homologous chromosome. For this reason, the genetic make-up of the observed trait is not twofold. If a man has a certain recessive genetic disposition on his X chromosome, this is called hemizygous and it gets phenotypically expressed. Also a recessive genetic disposition on his Y chromosome - also hemizygous - can come to expression, because there is no homologous chromosome with an allele, which could overlay it. If there is no genetic information on the Y chromosome for a certain trait, the effect of the Y is neutral and the allele on his X chromosome, which would be recessive in a heterozygous woman, can now alone come to expression.
Women have two homologous sex chromosomes (XX). Therefore, women can be carriers of X-linked genes. Examples of traits inherited via the X chromosome are color blindness and the most common hereditary form of Haemophilia. Men are affected much more often than women.[1][2]
Inheritance by female carriers
Queen Victoria, and her daughters Princesses Alice and Beatrix, were carriers of the hemophilia gene (an abnormal allele of a gene, necessary to produce one of the blood clotting factors). Both had children who continued to pass on the gene to succeeding generations of the royal houses of Spain and Russia, into which they married.[3] Since males only have one X chromosome, males who carried the altered gene had hemophilia B. Females have two X chromosomes, so one copy of an X-linked recessive gene would cause them to be an asymptomatic carrier. These females simply passed it to half of their children.[4]
Gonosomal dominant inheritances are also known. There are no carriers since owners of a dominant hereditary disposition phenotypically express the trait in each case.
^Potts, W.T.W. "Royal Haemophilia." Journal of Biological Education (Society of Biology) 30.3 (1996): 207. Academic Search Premier. 16 Sept. 2013
^Pagon, R. A.; Adam, M. P.; Ardinger, H. H. "Illustrated Glossary". GeneReviews. University of Washington, Seattle. Retrieved 15 December 2014.
February 16, 2024
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A hereditary carrier genetic carrier or just carrier is a person or other organism that has inherited a recessive allele for a genetic trait or mutation but usually does not display that trait or show symptoms of the disease Carriers are however able to pass the allele onto their offspring who may then express the genetic trait Punnett square If the other parent does not have the recessive genetic disposition it does not appear in the phenotype of the children but on the average 50 of them become carriers Carriers in autosomal inheritances edit nbsp Punnett square If both parents are carriers on the average 25 of the offspring have the recessive trait in phenotype and 50 are carriers Autosomal dominant recessive inheritance is made possible by the fact that the individuals of most species including all higher animals and plants have two alleles of most hereditary predispositions because the chromosomes in the cell nucleus are usually present in pairs diploid Carriers can be female or male as the autosomes are homologous independently from the sex In carriers the expression of a certain characteristic is recessive The individual has both a genetic predisposition for the dominant trait and a genetic predisposition for the recessive trait and the dominant expression prevails in the phenotype In an individual which is heterozygous regarding a certain allele it is not externally recognisable that it also has the recessive allele But if the carrier has a child the recessive trait appears in the phenotype in case the descendant receives the recessive allele from both parents and therefore does not possess the dominant allele that would cover the recessive trait According to Mendelian Law of Segregation of genes an average of 25 of the offspring become homozygous and express the recessive trait Carriers can either pass on normal autosomal recessive hereditary traits or an autosomal recessive hereditary disease Carriers in gonosomal inheritances edit nbsp The mother is a carrier of the recessive hereditary disposition for Color blindness The Y chromosome of the father cannot oppose this The healthy allele on the X chromosome of the father can compensate for this in a daughter She can see normally but she becomes a conductor The same pattern of inheritance applies to Haemophilia Gonosomal recessive genes are also passed on by carriers The term is used in human genetics in cases of hereditary traits in which the observed trait lies on the female sex chromosome the X chromosome The carriers are always women Men cannot be carriers because they only have one X chromosome The Y chromosome is not a really homologous chromosome For this reason the genetic make up of the observed trait is not twofold If a man has a certain recessive genetic disposition on his X chromosome this is called hemizygous and it gets phenotypically expressed Also a recessive genetic disposition on his Y chromosome also hemizygous can come to expression because there is no homologous chromosome with an allele which could overlay it If there is no genetic information on the Y chromosome for a certain trait the effect of the Y is neutral and the allele on his X chromosome which would be recessive in a heterozygous woman can now alone come to expression Women have two homologous sex chromosomes XX Therefore women can be carriers of X linked genes Examples of traits inherited via the X chromosome are color blindness and the most common hereditary form of Haemophilia Men are affected much more often than women 1 2 nbsp Inheritance by female carriersQueen Victoria and her daughters Princesses Alice and Beatrix were carriers of the hemophilia gene an abnormal allele of a gene necessary to produce one of the blood clotting factors Both had children who continued to pass on the gene to succeeding generations of the royal houses of Spain and Russia into which they married 3 Since males only have one X chromosome males who carried the altered gene had hemophilia B Females have two X chromosomes so one copy of an X linked recessive gene would cause them to be an asymptomatic carrier These females simply passed it to half of their children 4 Gonosomal dominant inheritances are also known There are no carriers since owners of a dominant hereditary disposition phenotypically express the trait in each case References edit Neil A Campbell Jane B Reece Biologie Spektrum Verlag 2003 ISBN 3 8274 1352 4 page 308 311 Ulrich Weber Biologie Gesamtband Oberstufe Cornelsen Verlag 2001 ISBN 3 464 04279 0 page 178 182 Potts W T W Royal Haemophilia Journal of Biological Education Society of Biology 30 3 1996 207 Academic Search Premier 16 Sept 2013 Pagon R A Adam M P Ardinger H H Illustrated Glossary GeneReviews University of Washington Seattle Retrieved 15 December 2014 Retrieved from https en wikipedia org w index php title Hereditary carrier amp oldid 1160457041, wikipedia, wiki, book, books, library,
