系谱分析

To understand how traits or disorders are inherited in humans, scientists analyze family trees also known as pedigrees.

In a typical pedigree, squares denote males, circles indicate females and a horizontal line between these shapes represents a mating.

If such a union produces children, a perpendicular line is drawn down from the parents towards any sons and daughters.

Thus progressively lower rows in the pedigree represent subsequent generations in a family.

For individuals that demonstrate a disease phenotype, like the skin rashes associated with biotinidase deficiency disorder where a person lacks the enzyme necessary to obtain vitamin B7, their associated shapes in the pedigree are shaded in.

By assessing which family members have been diagnosed with biotinidase deficiency, researchers can determine whether this disease results from a recessive or dominant mutation in a single gene, situated on an autosome or sex chromosome.

Here females and males are stricken at the same rate. Unafflicted parents have children with the disorder and not every generation contains a family member with the disease, a pattern that suggests biotinidase deficiency is autosomal recessive.

Importantly pedigree analysis not only elucidates inheritance patterns, but can also help couples understand their risk of having a child with the disorder given their family history.