Genetics Northern California



A biochemical phenomenon that determines, for certain genes, which one of the pair of alleles, the mother's or the father's, will be active in that individual.

In uteroIn the uterus or womb (Dorland's).
In vitro fertilization (IVF)

Combination of an egg and a sperm outside of the mother's body to create an embryo that is implanted in her uterus.

Inborn error of metabolism

Inherited diseases resulting from alterations in genes that code for enzymes.

InheritanceTransmission of genes from parent to offspring.
Inhibin-AInhibin-A (INH) is a hormone made by the placenta and the developing baby. Maternal blood levels remain relatively constant through the 15th and 20th weeks of pregnancy. Inhibin-A is only used in the calculation for the risk for Down syndrome.  Maternal blood levels of inhibin-A may be higher than usual in a pregnancy if the baby is affected with Down syndrome.

The insertion of a segment from one chromosome into another chromosome.

Insoluable fiberThis fiber cannot be absorbed by the body, but is passed through the intestine, and is found in vegetables, whole wheat, and whole grain cereals. It helps to treat both diarrhea and constipation.

Noncoding DNA sequences that interrupt the sequences containing instructions for making a protein (exons). Introns are not represented in messenger RNA; only the exons are translated into protein. The function of introns is still being explored.


A chromosomal mutation involving the removal of a chromosome segment, its rotation through l80 degrees, and its reinsertion in the same location. The replacement of a section of a chromosome in the reverse orientation.


A chromosome with two genetically and morphologically identical arms.


Intrauterine growth retardation. Determined by ultrasound, fetal size is smaller than expected by last menstrual period or a prior ultrasound.