Multiple allele
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General[edit | edit source]
If there are more than 2 alternative alleles for 1 locus in a population - this is referred to as a multiple allele.
- occurs in the inheritance of normal and pathological traits in humans
- e.g. gene for erythrocyte antigen A blood AB0 system can occur in up to 15 alleles
- similarly haemoglobinopathies- genetically determined by multiple alleles: the synthesis of Hb in humans is determined by 3 pairs of genes (polygenically determined), each of which has several alleles (polyalleles); thus, dozens of aberrant Hb types can arise
Allelic interactions[edit | edit source]
For more information see Allelic interactions.In a diploid cell, there are 2 alleles for a single gene. There can be 3 different relationships between these alleles, on which the final gene expression depends.
Incomplete dominance and recessiveness[edit | edit source]
- the dominant allele does not completely suppress the recessive allele, the recessive allele is also partially expressed.
- e.g. flower colour in a flower (A - red colour; a - white colour):
- homozygote AA - red colour
- homozygote aa - white colour
- heterozygote Aa - pink color
Complete dominance and recessiveness[edit | edit source]
- the dominant allele completely suppresses the expression of the recessive allele
- e.g. blood group in humans (A - agglutinogen A is formed; 0 - no agglutinogen is formed):
- homozygote AA - blood group A
- homozygote 00 - blood group zero
- heterozygote A0 - blood group A (agglutinogen A is formed)
Codominance[edit | edit source]
- both dominant alleles are fully expressed in the heterozygote and do not affect each other
- e.g. with human blood groups (alleles A and B are codominant to each other and dominant to allele 0):
- heterozygote A0 - group A
- heterozygote B0 - group B
- heterozygote AB - group AB (both agglutinogens are formed)
- homozygote AA - group A
- homozygote BB - group B
- homozygote 00 - group zero (no agglutinogen is formed)
References[edit | edit source]
Related articles[edit | edit source]
References[edit | edit source]
- ŠTEFÁNEK, Jiří. Medicína, nemoci, studium na 1. LF UK [online]. [cit. 11 February 2010]. <https://www.stefajir.cz/>.
- ŠÍPEK, Antonín. Genetika [online]. [cit. 11. 2. 2010]. <http://www.genetika-biologie.cz>.
