WHAT CAUSES BIOTINIDASE DEFICIENCY?

Biotinidase deficiency is a genetic condition.
Children with biotinidase deficiency have inherited two copies of the gene for biotinidase deficiency, one from each parent. Biotinidase deficiency is not caused by anything the parents did or did not do before or after a child was born.

Genes are units of genetic information.
The body's instructions for making the enzyme biotinidase are encoded in a pair of genes. Genes are tiny units of genetic information that tell the cells of our body to make certain products such as enzymes. We all have a unique set of 50,000-100,000 different genes, each coding for specific products or traits. The instructions are read from a unique code in the DNA, the material from which genes are made. If the instructions have an error in them, the gene product will not work properly.

Genes are packaged on the chromosomes.
Genes are organized into small thread-like packages called chromosomes, each of which contains about 2,000-5,000 genes. Each cell has 23 pairs of chromosomes, one member of each chromosome pair is inherited from each parent. There are 22 pairs of autosomes (non-sex chromosomes), and 1 pair of sex chromosomes (chromosomes that determine if a person is male or female).

Genes come in pairs, one from each parent.
Since chromosomes come in pairs, genes also come in pairs. One copy of each gene is inherited from one's mother and the other copy of each gene is inherited from one's father. Therefore, children share half of their genes with each parent, but also differ because of the genes received from the other parent. Brothers and sisters also share half of their genes, on the average, but they never inherit the exact same combination of genes unless they are identical twins.

Biotinidase deficiency is caused by having a pair of defective genes.
People with biotinidase deficiency receive a defective biotinidase gene from both of their parents. Since they do not have even one copy of the gene that codes for normal, active biotinidase, the activity of biotinidase in their bodies is very low or undetectable.