Babies with these defects have abnormal openings along the abdomen (stomach), so that intestines and other organs grow outside the baby’s body. An opening where the umbilical cord is attached is called omphalocele. This occurs in about 1 out of 4,000 births. An opening beside the umbilical cord is called gastroschisis. This occurs in about 1 out of 10,000 births. These openings may be present along with other birth defects. Surgery after birth can often repair an abdominal wall defect.

Please see the XAFP Program page and XAFP Program links section for more information.

Not normal; contrary to the usual structure, position, condition, behavior, or rule.

Individual(s) in a pedigree that exhibit the specific condition being studied.

One of the alternative versions of a gene that may occupy a given locus (gene site).

The situation in which there are different mutant alleles at the same locus (gene site), each capable of producing an abnormal phenotype.

The way amino acid disorders are inherited is called autosomal recessive. Please visit our metabolic autosomal recessive inheritance section, Metabolic Clinic page and Metabolic Clinic links section for more information.

The building blocks of proteins. These are coded for within the DNA.

A procedure used in prenatal diagnosis to obtain amniotic fluid. Amniotic fluid is withdrawn from the amniotic sac by syringe after insertion of a hollow needle into the sac through the abdominal and uterine wall.

Cells obtained by amniocentesis.

In molecular biology, the production of multiple copies of a sequence of DNA.

A condition in which the skull cap and brain do not develop.

Please see the Spina Bifida Clinic page , Spina Bifida Clinic links section, Genetic Counseling Program page, and Genetic Counseling Program links section for more information.

The term used to denote the progressively earlier appearance and increased severity of a disease in successive generations.

The occurrence together in a population of two or more phenotypic characteristics more often than expected by chance.

Any chromosome found in the cell nucleus other than the sex chromosomes. Humans typically have 22 pairs.

The empirically derived risk of a given condition or event in the population as a whole.

A pair of complementary nucleotide bases, as in double-stranded DNA. Used as the unit of measurement of the length of a DNA sequence.

The molecular building blocks of DNA and RNA. In DNA, adenine (A), thymine (T), guanine (G), and cytosine (C). In RNA, uracil (U) replaces thymine. In DNA, A bonds with T and C bonds with G. In RNA, A bonds with U and C bonds with G.

Not malignant. Having no deleterious affect.

Anomalous or atypical development of some aspect of the body present at birth.

The two genes most commonly associated with hereditary breast and/or ovarian cancer.

A flat, milky-brown, pigmented spot found on the skin.

An autosomal recessive disorder in which there is progressive deterioration of the central nervous system (brain).

A condition that involves the uncontrolled and abnormal division of eukaryotic cells. An informal term for a diverse class of diseases marked by uncontrolled cellular growth.

The production of cancerous growths.

Cancers occurring in the epithelial cells covering the surface of the body and lining the internal organs. Carcinomas account for about 90% of all cancer.

An individual who carries the abnormal gene for a specific condition (often, a recessive condition) without symptoms.

This term is used synonymously with sacral agenesis, since in most cases only the sacrum is involved. It is a loosely defined syndrome of vertebral malformations, ranging in severity from agenesis of the coccyx to absence of the sacral, lumbar, and even lower thoracic vertebrae. With high sacral and above malformations, there may be significant neurological deficits, as well as anomalies involving the genitourinary tract, intestines, and the respiratory system.

Please see the Spina Bifida Clinic page and Spina Bifida Clinic links section for more information.

A small, watery, membrane-bound compartment filled with chemicals; the basic subunit of any living thing.

The cycle of cell growth, replication of the genetic material, and nuclear and cytoplasmic division.

A procedure used for prenatal diagnosis in which a sample of the placenta, specifically the villous area of the chorion, is withdrawn either transabdominally or transcervically.

A pocket of fluid that collects in the choroid plexus of the brain. Benign in itself, the presence of a choroid plexus cyst in utero has been associated with an increased risk for Trisomy 18.

Please see the Genetic Counseling page and Genetic Counseling Program links section for more information.

Structures found in the nucleus of a cell which contain the genes. Chromosomes occur in pairs and a normal human cell contains 46 chromosomes, 22 pairs of autosomes and two sex chromosomes.

An incomplete closure of the top lip resulting in a separation or 'split' within the lip. This can be limited to one side (unilateral) or can occur on both sides (bilateral). Cleft lips can occur in isolation, with cleft palate, and/or as part of a syndrome.

Please see the Cleft Lip and Palate condition page, Cleft Lip and Palate links section, Craniofacial Clinic page and Craniofacial Clinic links section for more information.

An incomplete closure of the top or 'roof' of the mouth. This can occur in isolation, with a cleft lip, and/or as part of a syndrome.

Please see the Cleft Lip and Palate condition page, Cleft Lip and Palate links section, Craniofacial Clinic page and Craniofacial Clinic links section for more information.

The production of clinically different phenotypes from mutations in the same gene.

A group of genetically identical cells or organisms that are descended from one parent. In molecular biology,. a copy of DNA sequences created by recombinant DNA techniques.

A congenitally deformed foot which is twisted out of shape or position.

A triplet of three bases in a DNA or RNA molecule specifying a single amino acid.

The onset of pregnancy marked by fertilization of the egg by the sperm.

Mosaicism that is seen in the placenta but not the fetus.

Present at birth; not necessarily genetic.

The adrenal glands of babies with this disease do not make enough of the key stress-fighting hormone cortisol.  In about two-thirds of the cases, babies also do not produce enough of the salt-retaining hormone aldosterone. As a result, affected babies can develop dehydration, shock, and even death. Treatment with one or more oral medicines can help prevent these problems. Girls with this disorder may have the additional problem of having masculine-looking external genitals, which can be corrected with surgery.

Please see the State of California Newborn Screening Congenital Adrenal Hyperplasia (CAH) page for more information.

Abnormal development of the heart or of the blood vessels near the heart that is present at birth.

Relationship by descent from a common ancestor (blood relationship).

Individual requesting genetic counseling.

Genes physically close on a chromosome that express a phenotype when acting together.

Pertaining to the cranium(upper part of the head) and the face.

Premature closure of the sutures of the skull which can result in deformities.

Please see the Craniofacial Clinic page and Craniofacial Clinic links section for more information.

Chorionic Villus Sampling.

An autosomal recessive genetic condition of the exocrine glands which causes the body to produce excessively thick, sticky mucous that clogs the lungs and pancreas interfering with breathing and digestion.

Please see the Cystic Fibrosis condition page, Cystic Fibrosis links section, Genetic Counseling page and Genetic Counseling Program links section for more information.

Ductal carcinoma in situ. Cancer limited to the ducts of the breast. It may or may not become invasive.

A type of structural defect characterized by the abnormal form or position of a body part caused by mechanical force.

The loss of a sequence of DNA from a chromosome. The deleted DNA may be of any length from a single base to a large part of a chromosome.

Cognitive and/or motor delays in development. Progress/prognosis is dependent on the severity of delays and the underlying condition, but in most instances, children with delayed development never fully "catch up." Definition from Website: A slowing of the usual process of development particularly of cognitive skills.

The determination of the nature of a disease or condition.

Having a full set of genetic material consisting of paired chromosomes with one chromosome from each parent. In humans, the diploid chromosome number is 46.

The morphologic defect of an organ or larger region of the body resulting from the disturbance or destruction of an originally normal developmental process.

The product of fertilization of two separate eggs by two separate sperm; nonidentical twin pair. Compare to monozygotic.

Deoxyribonucleic acid; the molecule that encodes the genes responsible for the structure and function of living organisms and allows the transmission of genetic information from generation to generation.

Addition of a methyl group to a cytosine base in the DNA molecule. This process plays a role in gene expression that is not completely understood.

A characteristic of gene expression in which only one copy of a gene is needed in order for there to be manifestations of its presence.

A condition involving mental retardation due to the presence of an extra chromosome 21. Also called trisomy 21.

Please see the Down Syndrome condition page, XAFP Program page, XAFP Program Down Syndrome links section, Genetic Counseling page and Genetic Counseling Program links section for more information.

The presence of an extra copy of chromosomal material.

Reflecting abnormality in morphological development; abnormality in the development of structure or form.

Abnormality of development of particular tissue types; alteration in size, shape, or organization of cells into tissue.

Estimated date of confinement. Also known as EDD; estimated date of delivery. The expected delivery date of a pregnancy.

Electroencephalogram. A recording of the brain waves.

In molecular biology, a method of separating large molecules such as DNA fragments or proteins from a mixture of similar molecules.

In humans, the developing organism from the end of the second week after fertilization to the end of the eighth week.

Electromyogram. A recording of muscular activity during rest, during voluntary contractions, and during electrical stimulation.

A neural tube defect that occurs when there is an opening in the bones of the skull through which brain tissue protrudes.

Please see the Spina Bifida Clinic page, Spina Bifida Clinic links section, Genetic Counseling page and Genetic Counseling Program links section for more information.

A protein that facilitates a specific chemical reaction.

A cell having any number of complete chromosome sets or an individual composed of such cells.

Expanded alphafetoprotein test. A prenatal screening test which measures four analytes in maternal blood to estimate the risk of certain fetal anomalies. Currently, the test screens for neural tube defects (NTDs)/abdominal wall defects, Down syndrome, trisomy 18, and Smith-Lemli-Opitz syndrome (SLOS).

A transcribed region of a gene that is present in mature messenger RNA. The region(s) of the gene coding for proteins.

In relation to autosomal inheritance, a term referring to the extent to which a genetic condition is expressed. If there is variable expressivity, the trait may vary in expression from mild to severe but it is never completely unexpressed, i.e., an individual will have some symptoms but they can vary from mild to severe.

A test result in which an affected individual is incorrectly identified as being unaffected with the disease in question.

A test result in which an unaffected individual is incorrectly identified as being affected with the disease in question.

Characteristic of some or all members of a family.

This is an abnormality in cholesterol metabolism where the individual has either an elevated LDL cholesterol or an elevated triglyceride, or both. Some members in the family can have only the elevated LDL or only the elevated triglyceride, and some may have both abnormalities.

Please see the FCH condition page, Lipid Clinic page and Lipid Clinic links section for more information.

An autosomal recessive neurological disorder that affects the autonomic and sensory nervous systems beginning in infancy. There is a wide range of symptoms that can vary greatly between affected individuals. These symptoms include difficulty swallowing (which can lead to frequent pneumonia), lack of overflow tear production, inappropriate perception of heat, pain and taste, postural hypotension/episodic hypertension, gastrointestinal dysmotility, speech and motor incoordination, poor growth, scoliosis, and autonomic crisis (episodes of vomiting, high blood pressure, sweating, and fever). The average age of death is 30 years. There is no known cure for this condition. All confirmed cases of familial dysautonomia have been in individuals of Ashkenazi Jewish ancestry.

This is an abnormality in cholesterol metabolism where the individual has an elevated total cholesterol and an elevated LDL.

Please see the FH condition page, Lipid Clinic page and Lipid Clinic links section for more information.

See pedigree

An autosomal dominantly inherited predisposition to multiple adenomatous polyps of the colon and a high risk of colon cancer.

The way fatty acid oxidation disorders are inherited is called autosomal recessive. Please visit our metabolic autosomal recessive inheritance section, Fatty Acid Oxidation Disorders condition page , Metabolic Clinic page and Metabolic Clinic links section for more information.

A molecular cytogenetic technique in which labeled probes are hybridized with chromosomes and visualized under a fluorescence microscope. Can detect microdeletion syndromes, trisomies and other genetic conditions.

A vitamin that helps to prevent birth defects such as spina bifida and other neural tube defects in the newborn. Found in leafy green vegetables, liver, legumes, yeast, and some fruits. Important component of multivitamins and prenatal vitamins.

A change in DNA in which a duplication or deletion occurs that is not a multiple of three base pairs.

A disorder that occurs when the body lacks an enzyme needed to process galactose, or milk sugar. When the enzyme is missing, galactose builds up in the body and causes damage to the brain, liver, eyes, and kidneys. Newborns with untreated galactosemia can die within the first few weeks of life. Galactosemia is treated with a galactose-restricted diet. For infants, this means the use of a soy formula. Early detection and prompt dietary treatment can decrease the problems associated with galactosemia.

Please see our Metabolic Clinic program page, Galactosemia condition page or the State of California Newborn Screening Galactosemia page for more information.

Ovum or female egg cell or male sperm. Germ cell.

Units of heredity which control growth, development and function of organisms. Located on chromosomes, genes carry information from one generation to the next. A gene is comprised of a continuous sequence of DNA necessary to encode a functional protein. Our body has about 50,000 to 100,000 genes, each of which contains the code for a specific product, typically, a protein such as an enzyme.

The process by which the information encoded in a gene is converted into protein or some form of RNA. The DNA sequence is first transcribed into RNA and then usually, but not always, translated into protein.

Group of closely related genes that make similar products. 

The ordering of genes on chromosomes according to recombination frequency.

The total of all genes in a population.

Treating disease by replacing, manipulating, or supplementing nonfunctional genes.

The instructions in a gene that tell the cell how to make a specific protein. A, T, G, and C are the "letters" of the DNA code which stand for the chemicals adenine, thymine, guanine, and cytosine, respectively. The code combines the four chemicals in various ways to spell out 3-letter "words" that specify which amino acid is needed at every step in making a specific protein.

An educational counseling process for individuals and families who either have a genetic disease, who are at risk to develop such disease, and/or who are at risk to have a baby with a genetic disease. Genetic counseling provides patients with information about their condition and helps them make informed decisions.

Health professionals with specialized education, training, and experience in medical genetics and counseling.

Testing a population group to identify a subset of individuals at high risk for having or transmitting a specific genetic disorder

Referring to clinical geneticist. An individual with an MD and/or PhD degree with specialized training in diagnosing genetic conditions.

The study of heredity and inheritance of traits.

All the genetic material in the chromosomes of a particular organism.

The actual genes carried by an individual (distinct from phenotype).

Ovum or female egg cell or male sperm. Gamete

Also referred to as germline mosaicism, meaning an individual may carry two or more genetically different types of germline cells.

A single set of chromosomes (half the full set of genetic material) present in the egg and sperm cells. Human beings have 23 chromosomes in their reproductive cells. All other cells are diploid.

The measurement of the circumference of the head.

Inherited disorders in which the production of normal hemoglobins is partly or completely suppressed or partly or completely replaced by the production of one or more abnormal hemoglobin variants.
Classification of hemoglobinopathies:
(a) defects leading to the production of abnormal protein molecule. Abnormalities result mainly from the substitution of one amino acid for another in one of the normal polypeptide chains (?, ?, ?, or ?) mainly ? and ? of the normal adult hgb.
(b) defects leading to the reduction of protein synthesis. This group includes the thalassemias (heterogeneous group f genetic disorders) characterized by imbalanced globin chain production which leads to anemia, ineffective erythropoeisis and red cell destruction.
(c) defects leading to developmental abnormalities of no clinical importance and concern.

Please see the Hemoglobinopathy Program page and Hemoglobinopathy Program links section for more information.

An individual that has two different alleles or genes encoding a protein; one copy encodes a normal protein whereas the second copy encodes a nonfunctional or abnormal protein. Also, two different copies of normal alleles.

Presence of excessive bodily and facial hair.

Hereditary nonpolyposis colorectal cancer. Autosomal dominantly inherited disease predisposing to colorectal cancer. May be in association with carcinoma of the endometrium, ovary, stomach, small bowel, and pancreas.

A short stretch of nucleotides whose base sequence is virtually identical in all the genes that contain it. Found in many organisms from fruit flies to human beings.

An individual that has two identical alleles or genes encoding a protein. Genes may encode functional or nonfunctional proteins.

Genes whose protein products are required for cellular maintenance or metabolism.

A large international project to map and sequence all the DNA in human chromosomes.

The process of joining two complementary strands of DNA or one each of DNA and RNA to form a double-stranded molecule. 

A condition that is caused by the build up of fluid inside the developing brain due to the partial blockage of the normal flow of spinal fluid out of the brain.

Please see the Spina Bifida Clinic page and Spina Bifida Clinic links section for more information.

This condition is a mild form of achondroplasia. People with hypochondroplasia have rhizomelic (upper limb) short stature with adult heights varying from 3'10" to 5'5. It is usually diagnosed between ages 1 and 3 when growth slows down significantly. Hypochondroplasia can have some of the same medical complications seen in achondroplasia, but these occur much less frequently and with less severity. These potential complications include: conductive hearing loss and speech delay secondary to chronic otitis media (ear infections), decreased elbow extension, bowed legs, and benign ventriculomegaly or hydrocephalus (rare). There is an unexplained increased risk of mental retardation (10-20%). 70% of cases are due to mutations in the FGFR3 gene (same gene as achondroplasia).

A defect of the underside (ventral) portion of the penis where the urethra canal is open in places.

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.

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

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

Transmission of genes from parent to offspring.

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

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, baby's growth is not commensurate with dates.

A photomicrograph of an individual's chromosomes arranged in a standard format showing the number, size, and shape of each chromosome.

Unit of length for DNA fragments equal to 1000 nucleotides. 

People with Kniest dysplasia are usually diagnosed at birth and can be expected to reach an adult height of 100-145cm. Features include: a short-trunk and short limbs (limbs look long in comparison to trunk), round face, myopia and other significant eye complications, conductive or mixed hearing loss, enlarged joints and joint contractures, and curves in the spine (kyphoscoliosis) which may cause restrictive lung disease. Some individuals also have clubfeet and/or cleft palate.

Lobular carcinoma in situ. Abnormal cells within the lobule which don't form lumps. They can serve as a marker for future breast cancer risk.

Large for gestational age.

A defect of primary neurulation resulting from incomplete fusion of the posterior neural tube. A slender stalk of neural tissue extends through the nuchal fascia into the myelomeningocele sac.

Please see the Spina Bifida Clinic page and Spina Bifida Clinic links section for more information.

The occurrence of different genes on the same chromosome that are usually inherited together.

A spinal cord lipoma associated with an underlying spina bifida lesion. Often, the fatty tissue of the lipoma extends into the spinal canal, and may press on the spinal cord, resulting in progressive neurological deterioration.

Please see the Spina Bifida Clinic page and Spina Bifida Clinic links section for more information.

First day of LMP is date used to determine the gestational age of the fetus and predict date of delivery.

The position or place on a chromosome occupied by a particular gene or one of its alleles.

A statistical estimate of whether two loci are likely to lie near each other on a chromosome and therefore are likely to be inherited together. A LOD score of 3 or more is generally taken to indicate that the two loci are linked (see linkage).

A condition, either present at birth or acquired, where the head is abnormally large.

A single localized poor formation of tissue that initiates a chain of subsequent defects in the developing fetus.

In reference to neoplasm, having the property of locally invasive and destructive growth and metastasis. Compare to benign.

MSUD is a condition that occurs when the body is missing one of the enzymes needed to break down (metabolize) protein. Without this enzyme, parts of the protein build up in the body causing damage to the nervous system, especially the brain. If left untreated, MSUD can result in mental retardation, seizures, coma, and even death.

Please visit our Maple Syrup Urine Disorder condition page, metabolic autosomal recessive inheritance section, Metabolic Clinic page and Metabolic Clinic links section for more information.

See gene mapping

Two successive nuclear divisions (with corresponding cell divisions) that produce haploid gametes.

A protrusion of the meninges, without brain or spinal cord, through a defect in the spine or skull. The defect is covered with skin. If occurring on the spine, there is often a bulge in the midline of the back where the abnormality is located. Although there is frequently less nerve damage initially, complications can occur later from tethering of the spinal cord.

Please see the Spina Bifida Clinic page and Spina Bifida Clinic links section for more information.

The term given to an individual with an IQ score below 70 (average = 100). A disability that affects a person's intellectual functioning and is accompanied by significant limitations in areas such as communication, self-care, work, leisure, health, safety, and interpersonal skills. Onset must occur before age 18 years.

Conditions that affect the body’s ability to use amino acids (from proteins), organic acids (from proteins, fats, and sugars) or fatty acids (from fats) all of which are necessary for energy, growth and repair. To break down or convert these substances, certain enzymes must be present. When there is a deficiency or absence of the needed enzyme (block in the metabolic pathway), metabolites build up in large amounts and may be harmful to the body. Metabolic disorders have varying degrees of severity. If identified early, many of these disorders can be treated before they cause serious health problems. Without treatment, some of these disorders may lead to severe illness and death. Treatment may include close monitoring of the child’s health, medication, dietary supplements, and/or special diets including medical formulas and foods.

Please see our Metabolic Clinic page, Metabolic Clinic links section, and the State of California Newborn Screening metabolic disorders page for more information.

The chemical reaction that occur in living cells, both synthesis and degradation.

Please see condition page for Cartilage Hair Hypoplasia (CHH).

A rare form of dwarfism that primarily affects the metaphyses (growing portion of the bone under the cartilaginous growth plate). It causes short stature with abnormally short arms and legs in proportion to the trunk, bowed legs, flared rib cage and waddling gait. There are almost always hip deformities (coxa vara) and leg pain.

The spread of cancer to another organ, usually through the bloodstream.

The way methlymalonic acidemia is inherited is called autosomal recessive. The way fatty acid oxidation disorders are inherited is called autosomal recessive. Please visit our metabolic autosomal recessive inheritance section, Methlymalonic Acidemia condition page, Metabolic Clinic page and Metabolic Clinic links section for more information.

There were originally 3 types of this condition, but now there is a discussion to combine Types I and III. All types have very slow growth (adult height < 100cm), small slender bones, and microcephaly (small head). The main difference between Types I (& III) and II are the facial features and development. People with Type I have a prominent nose and sloping forehead and poor development whereas those with Type II have a round face, large-appearing eyes, flat midface and a long, curved nose. Type II also has a better, though not necessarily average, developmental outcome.

Abnormal smallness of the head. Head circumference which is below the 3^rd percentile.

A chromosome deletion too small to be visible under a microscope. May be visualized using FISH. See FISH

A type of mutation that results in a single amino acid change in the translated gene product.

A membrane-bounded structure in the interior of the cell that generates energy for the cell. Generally inherited from the mother.