Hemizygosity
In biology , especially in genetics , hemizygosity is the condition in which only one allele of a gene occurs in the otherwise doubled ( diploid ) set of chromosomes. One also speaks of a hemizygotic inheritance .
In humans, this affects the genes on the sex chromosomes in males , as their chromosome pair consists of an X chromosome and a (much smaller) Y chromosome . Male individuals are therefore hemizygous with regard to all genes only present on the X and only on the Y chromosome . As a result, recessive features are also expressed if they are on this simply existing (haploid) chromosome. This is the reason why some hereditary diseases affect male offspring much more often than female offspring (for example hemophilia ).
This is to be distinguished from heterozygosity , the genetic makeup with duplicate but different genes, so-called alleles . In heterozygosity, the gene is present twice, but each allele only once.
See also
swell
- Jan Murken, Hartwig Clewe (Ed.): Human Genetics . Ferdinand Enke Verlag, Stuttgart 1996, 6th edition. ISBN 3-432-88176-2 .