Inheritance of hypophosphatasia

Medical Hypotheses
|September 1, 1985
PubMed

A system of multiple, codominant alleles (HN, HC, HI) is proposed for the inheritance of hypophosphatasia. These alleles are associated with a single autosomal locus which determines the presence or absence of hypophosphatasia among human subjects. Either HC or HI conditions hypophosphatasia whereas HN conditions the absence of this disorder. Only one genotype, HNHN, produces the absence of hypophosphatasia. Either HNHC or HNHI produces adult hypophosphatasia. Either HCHC or HCHI produces childhood hypophosphatasia. Only HIHI produces infantile (neonatal) hypophosphatasia. HI is lethal only in a homozygous state. HN occurs at a much higher frequency in human populations than either HC or HI. Any one of the hypophosphatasic genotypes is thought to exert the same degree of epistatic effect on enzyme activity within the bone/liver/kidney complex of alkaline phosphatases. These alleles and genotypes are considered to be completely penetrant but show variable expressivity within each class of hypophosphatasia.

Related Concept Videos

Pedigree Analysis01:35

Pedigree Analysis

Overview
Pleiotropy01:33

Pleiotropy

Pleiotropy is the phenomenon in which a single gene impacts multiple, seemingly unrelated phenotypic traits. For example, defects in the SOX10 gene cause Waardenburg Syndrome Type 4, or WS4, which can cause defects in pigmentation, hearing impairments, and an absence of intestinal contractions necessary for elimination. This diversity of phenotypes results from the expression pattern of SOX10 in early embryonic and fetal development. SOX10 is found in neural crest cells that form melanocytes,...
Sex-linked Disorders01:43

Sex-linked Disorders

Like autosomes, sex chromosomes contain a variety of genes necessary for normal body function. When a mutation in one of these genes results in biological deficits, the disorder is considered sex-linked.
Genomic Imprinting and Inheritance02:30

Genomic Imprinting and Inheritance

Diploid organisms inherit genetic material through chromosomes from both parents. Copies of the same gene are known as alleles. In most cases, both alleles are simultaneously expressed and allow various cellular processes to function optimally. If one of the alleles is missing or mutated, the expression of the other allele can compensate; however, this is not true for all genes.
The expression of some genes depends on which parent passed the gene to the offspring, through a phenomenon known as...
The Retinoblastoma Gene01:20

The Retinoblastoma Gene

Tumor suppressor genes are normal genes that can slow down cell division, repair DNA mistakes, or program the cells for apoptosis in case of irreparable damage. Hence, they play an essential role in preventing the proliferation of damaged cells.
The first-ever tumor suppressor gene called Rb was identified in retinoblastoma - a rare eye tumor in children. In inherited forms of the disease, a child inherits one defective copy of the Rb gene, which predisposes them to retinoblastoma. However,...
Huntington Disease l: Introduction01:21

Huntington Disease l: Introduction

Huntington disease or HD is a progressive, fatal neurodegenerative disorder inherited in an autosomal dominant pattern.PathophysiologyIt is caused by expansion of the CAG trinucleotide repeat in the HTT gene on chromosome 4 (4p16.3), producing an abnormal huntingtin protein with an expanded polyglutamine tract. This misfolded protein disrupts cellular function, leading to neuronal death. Normal alleles have ≤26 repeats, 27–35 are intermediate (risk of expansion), 36–39 show reduced penetrance,...