Glossary of Terms

Definition of key words associated with the diagnosis, care, and research of Turner Syndrome.

The environment or community concerned with the pursuit of research, education, and scholarship.

A family planning option to legally take another’s child and bring it up as one’s own.

An unwanted reaction caused by the administration of a drug or treatment. Adverse events may include headache, nausea, skin irritation, or other physical problems.

Organizations and groups that actively support participants and their families with valuable resources, including self-empowerment and survival tools.

An autoimmune disease that develops when the body attacks its own hair follicles. A person’s genetic makeup, combined with other factors, triggers this form of hair loss. People with alopecia areata may have a higher risk for other autoimmune diseases such as thyroid disease or vitiligo (patches of lighter skin appear).

A medical procedure for the purpose of diagnosing chromosomal and neural tube disorders, usually after 16 weeks of pregnancy. The procedure involves obtaining amniotic fluid containing fetal DNA which is examined for genetic abnormalities.

The large arterial trunk that carries blood from the heart to be distributed by branch arteries through the body.(Webster)

An aortic dissection is a serious condition in which a tear develops in the inner layer of the aorta, the large blood vessel branching off the heart. Blood surges through this tear into the middle layer of the aorta, causing the inner and middle layers to separate (dissect). If the blood-filled channel ruptures through the outside aortic wall, aortic dissection is often fatal. (Mayo)

The vessels carrying blood away from the heart. (MeSH)

An autosome is any of the numbered chromosomes, as opposed to the sex chromosomes. Humans have 22 pairs of autosomes and one pair of sex chromosomes (the X and Y). Autosomes are numbered roughly in relation to their sizes. That is, Chromosome 1 has approximately 2,800 genes, while chromosome 22 has approximately 750 genes.

Not typical: not like the usual or normal type. (Webster)

A base pair is two chemical bases bonded to one another forming a “rung of the DNA ladder.” The DNA molecule consists of two strands that wind around each other like a twisted ladder. Each strand has a backbone made of alternating sugar (deoxyribose) and phosphate groups. Attached to each sugar is one of four bases–adenine (A), cytosine (C), guanine (G), or thymine (T). The two strands are held together by hydrogen bonds between the bases, with adenine forming a base pair with thymine, and cytosine forming a base pair with guanine.

Studies that increase understanding of fundamental clinical hypotheses or principles: this can be thought of as a research hypothesis that arises out of curiosity. In the long term this type of research can become the basis for a drug to enter human study, or clinical trials. Basic research is often conducted at an academic, university level.

When an evaluation or judgment cannot be impartial or objective.

Bioinformatics is a subdiscipline of biology and computer science concerned with the acquisition, storage, analysis, and dissemination of biological data, most often DNA and amino acid sequences. Bioinformatics uses computer programs for a variety of applications, including determining gene and protein functions, establishing evolutionary relationships, and predicting the three-dimensional shapes of proteins.

A birth defect is an abnormality present at birth. Also called a congenital defect, it can be caused by a genetic mutation, an unfavorable environment during pregnancy, or a combination of both. The effect of a birth defect can be mild, severe, or incompatible with life.

A clinical trial is called “double blind” when both volunteers and researchers do not know which groups volunteers are assigned to in a study. A trial is “single blind” when only the volunteers are unaware of the group they are assigned to in the study.
Candidate Gene

A candidate gene is a gene whose chromosomal location is associated with a particular disease or other phenotype. Because of its location, the gene is suspected of causing the disease or other phenotype.

A caregiver is anyone who provides physical, emotional, spiritual, financial, or logistical support to a loved one with a chronic, disabling or life-threatening illness.  Caregivers benefit from learning about and creating strategies to manage ongoing care, treatments and support, while gaining a greater sense of control, community, and hope.

Carrier screening is a type of genetic testing performed on people who display no symptoms for a genetic disorder but may be at risk for passing it on to their children. A carrier for a genetic disorder has inherited one normal and one abnormal allele for a gene associated with the disorder. A child must inherit two abnormal alleles in order for symptoms to appear. Prospective parents with a family history of a genetic disorders are candidates for carrier screening.

A cell is the basic building block of living things. All cells can be sorted into one of two groups: eukaryotes and prokaryotes. A eukaryote has a nucleus and membrane-bound organelles, while a prokaryote does not. Plants and animals are made of numerous eukaryotic cells, while many microbes, such as bacteria, consist of single cells. An adult human body is estimated to contain between 10 and 100 trillion cells.

A cell cycle is a series of events that takes place in a cell as it grows and divides. A cell spends most of its time in what is called interphase, and during this time it grows, replicates its chromosomes, and prepares for cell division. The cell then leaves interphase, undergoes mitosis, and completes its division. The resulting cells, known as daughter cells, each enter their own interphase and begin a new round of the cell cycle.

The process by which cells multiply involving both nuclear and cytoplasmic division. (Miriam Webster)

The cell membrane, also called the plasma membrane, is found in all cells and separates the interior of the cell from the outside environment. The cell membrane consists of a lipid bilayer that is semipermeable. The cell membrane regulates the transport of materials entering and exiting the cell.

CVS utilizes either a catheter or needle to biopsy placental cells that are derived from the same fertilized egg as the fetus. The chorionic villi are wispy projections of placental tissue that share the baby’s genetic makeup. Chorionic villus sampling is usually done between weeks 10 and 13 of pregnancy — earlier than other prenatal diagnostic tests, such as amniocentesis.

A chromosome is an organized package of DNA found in the nucleus of the cell. Different organisms have different numbers of chromosomes. Humans have 23 pairs of chromosomes–22 pairs of numbered chromosomes, called autosomes, and one pair of sex chromosomes, X and Y. Each parent contributes one chromosome to each pair so that offspring get half of their chromosomes from their mother and half from their father.

A chromosome abnormality reflects an abnormality of chromosome number or structure. Most chromosome abnormalities occur as an accident in the egg or sperm. Therefore, the abnormality is present in every cell of the body. Some abnormalities, however, can happen after conception, resulting in mosaicism, where some cells have the abnormality and some do not.

Chromosome studies are often performed on parents when a child is found to have an abnormality. Chromosomal bnormalities can be inherited from a parent (such as a translocation) or be “de novo” (new to the individual).

A medical researcher in charge of carrying out a clinical trial’s protocol.

Clinical trials investigating dosage, safety, efficacy and potential outcomes of drugs in disease-specific populations through controlled trials. There are typically three stages of clinical trials that must be performed before a drug may be submitted to the Food & Drug Administration (FDA) for approval. Prior to commencing a clinical trial, a drug must have demonstrated safety and efficacy in a laboratory model.

A complex disease is caused by the interaction of multiple genes and environmental factors. Complex diseases are also called multifactorial. Examples of complex diseases include cancer and heart disease.

A secondary disease or condition that develops in the course of a primary disease or condition and arises either as a result of it or from independent causes. (Miriam-Webster’s Medical)

Congenital conditions are those present from birth. Birth defects are described as being congenital. They can be caused by a genetic mutation, an unfavorable environment in the uterus, or a combination of both factors.

In many clinical trials, one group of volunteers will be given an experimental drug or treatment, while the control group is given either a standard treatment for the illness or a placebo.

The aorta carries blood from the heart to the vessels that supply the body with blood and nutrients. If part of the aorta is narrowed, it is hard for blood to pass through the artery.

Cystic hygroma and lymphedema occur in many conceptuses with TS as a consequence of lymphatic malformations and obstruction, primarily at the communication between the jugular lymphatic sac and the internal jugular vein (377). The presence of a frank cystic hygroma, however, makes the diagnosis of TS more likely (39). Many of the severely affected fetuses fail to survive (379).

A cytogeneticist is a geneticist who specializes in the study of chromosomes and the structure and function of the cell.

Cytogenetics is the branch of genetics that studies the structure of DNA within the cell nucleus. This DNA is condensed during cell division and form chromosomes. The cytogenetic studies the number and morphology of chromosomes. Using chromosome banding techniques (classical cytogenetics) or hybridization fluorescently labeled probes (molecular cytogenetics). The number and morphology of chromosomes in a cell of a particular species are always constant, in most cells of the body (with the exception of reproductive cells and others such as the liver). This is a characteristic of each specie, in humans such as the number of chromosomes is 46.

An independent committee that reviews data while a clinical trial is in progress to ensure that volunteers are not exposed to undue risk. A DSMB may recommend that a clinical trial be halted if there are safety concerns or if the trial objectives have been met.

Deletion is a type of mutation involving the loss of genetic material. It can be small, involving a single missing DNA base pair, or large, involving a piece of a chromosome.

A chromosome abnormality that occurred in the individual and was not inherited from the parents.

Diabetes mellitus is a disease characterized by an inability to make or use the hormone insulin. Insulin is needed by cells to metabolize glucose, the body’s main source of chemical energy. Type I diabetes, also called insulin-dependent diabetes mellitus, is usually caused by an autoimmune destruction of insulin-producing cells. Type II diabetes, also called non-insulin-dependent diabetes mellitus, occurs when cells become resistant to the effects of insulin.

Delays in any or all areas including cognitive, social, language, sensory, and emotional development. (Unified Medical Language Systems)

Developmental disabilities are severe, life-long disabilities attributable to mental and/or physical impairments which manifest themselves before the age of 22 years and are likely to continue indefinitely.  They result in substantial limitations in three or more of the following areas:  self-care; comprehension and language; skills (receptive and expressive language); learning; mobility; self-direction; capacity for independent living; economic self-sufficiency; ability to function independently without coordinated services (continuous need for individually planned and coordinated services for housing, employment, education, civil and human rights protection, health care to live in the community. (ADD)

Diploid is a cell or organism that has paired chromosomes, one from each parent. In humans, cells other than human sex cells, are diploid and have 23 pairs of chromosomes. Human sex cells (egg and sperm cells) contain a single set of chromosomes and are known as haploid.

DNA is the chemical name for the molecule that carries genetic instructions in all living things. The DNA molecule consists of two strands that wind around one another to form a shape known as a double helix. Each strand has a backbone made of alternating sugar (deoxyribose) and phosphate groups. Attached to each sugar is one of four bases–adenine (A), cytosine (C), guanine (G), and thymine (T). The two strands are held together by bonds between the bases; adenine bonds with thymine, and cytosine bonds with guanine. The sequence of the bases along the backbones serves as instructions for assembling protein and RNA molecules.

DNA replication is the process by which a molecule of DNA is duplicated. When a cell divides, it must first duplicate its genome so that each daughter cell winds up with a complete set of chromosomes.

DNA sequencing is a laboratory technique used to determine the exact sequence of bases (A, C, G, and T) in a DNA molecule. The DNA base sequence carries the information a cell needs to assemble protein and RNA molecules. DNA sequence information is important to scientists investigating the functions of genes. The technology of DNA sequencing was made faster and less expensive as a part of the Human Genome Project.

Dominant refers to the relationship between two versions of a gene. Individuals receive two versions of each gene, known as alleles, from each parent. If the alleles of a gene are different, one allele will be expressed; it is the dominant gene. The effect of the other allele, called recessive, is masked.

Double helix is the description of the structure of a DNA molecule. A DNA molecule consists of two strands that wind around each other like a twisted ladder. Each strand has a backbone made of alternating groups of sugar (deoxyribose) and phosphate groups. Attached to each sugar is one of four bases: adenine (A), cytosine (C), guanine (G), or thymine (T). The two strands are held together by bonds between the bases, adenine forming a base pair with thymine, and cytosine forming a base pair with guanine.

Refers to any abnormality, anatomical or biochemical, evident at birth or during the neonatal period. (Unified Medical Language Systems)

A mature haploid female germ cell extruded from the ovary at ovulation. (Unified Medical Language System)

Embryo Cryopreservation is the process of freezing and preserving an unborn offspring that is in the process of development.

Emotional Intelligence is different than IQ, it is the ability to identify, assess, and control the emotions of oneself, of others, and of groups. Various models and definitions have been proposed of which the ability and trait EI models are the most widely accepted in the scientific literature. Criticisms have centered on whether the construct is a real intelligence and whether it has incremental validity over IQ and the Big Five personality dimensions. Wiki

An endocrinologist is a specialist provider that studies and cares for hormonal conditions that are often complex and involve many glandular systems within your body. Your primary care doctor refers you to an endocrinologist when you have a problem with your endocrine system.

The study of a disease within certain populations; research in this area can lead to better understanding of potential risk factors, including occupational or environmental exposures, that can lead to development of a disease.

A family history is a record of medical information about an individual and their biological family. Human genetic data is becoming more prevalent and easy to obtain. Increasingly, this data is being used to identify individuals who are at increased risk for developing genetic disorders that run in families.

Fraternal twins are also dizygotic twins. They result from the fertilization of two separate eggs during the same pregnancy. Fraternal twins may be of the same or different sexes. They share half of their genes just like any other siblings. In contrast, twins that result from the fertilization of a single egg that then splits in two are called monozygotic, or identical, twins. Identical twins share all of their genes and are always the same sex.

The gene is the basic physical unit of inheritance. Genes are passed from parents to offspring and contain the information needed to specify traits. Genes are arranged, one after another, on structures called chromosomes. A chromosome contains a single, long DNA molecule, only a portion of which corresponds to a single gene. Humans have approximately 23,000 genes arranged on their chromosomes.

Gene mapping is the process of establishing the locations of genes on the chromosomes. Early gene maps used linkage analysis. The closer two genes are to each other on the chromosome, the more likely it is that they will be inherited together. By following inheritance patterns, the relative positions of genes can be determined. More recently, scientists have used recombinant DNA (rDNA) techniques to establish the actual physical locations of genes on the chromosomes.

A genetic marker is a DNA sequence with a known physical location on a chromosome. Genetic markers can help link an inherited disease with the responsible gene. DNA segments close to each other on a chromosome tend to be inherited together. Genetic markers are used to track the inheritance of a nearby gene that has not yet been identified, but whose approximate location is known. The genetic marker itself may be a part of a gene or may have no known function.

Identifying the role of a gene, or genes, that are important in the development of a disease. Research in this area could uncover specific chromosomes (either present or absent) that may be predictive of the likelihood of developing a disease and the rate of disease progression. It is important to note that there may be interplay between environmental factors and gene expression. Similarly certain environmental factors could result in gene alterations or mutations. Better understanding of the genetic markers of a disease, could lead to earlier diagnosis and treatment, new novel therapies, and ultimately disease prevention.

Genetic screening is the process of testing a population for a genetic disease in order to identify a subgroup of people that either have the disease or the potential to pass it on to their offspring.

Genetic testing is the use of a laboratory test to look for genetic variations associated with a disease. The results of a genetic test can be used to confirm or rule out a suspected genetic disease or to determine the likelihood of a person passing on a mutation to their offspring. Genetic testing may be performed prenatally or after birth. Ideally, a person who undergoes a genetic test will discuss the meaning of the test and its results with a genetic counselor.

The genome is the entire set of genetic instructions found in a cell. In humans, the genome consists of 23 pairs of chromosomes, found in the nucleus, as well as a small chromosome found in the cells’ mitochondria. These chromosomes, taken together, contain approximately 3.1 billion bases of DNA sequence.

Genomics refers to the study of the entire genome of an organism whereas genetics refers to the study of a particular gene.

A genotype is an individual’s collection of genes. The term also can refer to the two alleles inherited for a particular gene. The genotype is expressed when the information encoded in the genes’ DNA is used to make protein and RNA molecules. The expression of the genotype contributes to the individual’s observable traits, called the phenotype. (NHGRI)

An alternate family planning option is a gestational surrogacy with embryo from both intended parents. A surrogate is implanted with an embryo created by IVF, using intended father’s sperm and intended mother’s eggs.

Various treatment modalities that produce the desired therapeutic effect by means of change of hormone/hormones level. The treatment may include administration of hormones or hormone analogs to the patient, or decreasing the level of hormones in the body by using hormone antagonists, or hormone ablation therapy. The concept covers but not limited to: intermittent or permanent hormone suppression or ablation in treatment of hormone-dependent tumors, hormone replacement therapy of any kind, hormonal component of gender reassignment therapy, hormonal contraception, surgical and radiation castration. (Unified Medical Language Systems)

Identical twins are also known as monozygotic twins. They result from the fertilization of a single egg that splits in two. Identical twins share all of their genes and are always of the same sex. In contrast, fraternal, or dizygotic, twins result from the fertilization of two separate eggs during the same pregnancy. They share half of their genes, just like any other siblings. Fraternal twins can be of the same or different sexes.

The Individuals with Disabilities Education Act (IDEA) is the landmark, cutting edge federal legislation that governs special eduction ( for children ages 3 to 21 years) and early intervention services (ages birth to 3 years) in the United States.  Legislation guaranteeing a Free and Appropriate Public Education to children with special needs began in 1975.  However, early legislation supporting children with special needs dates back to the 1960’s.  The Federal Law did not include Early Intervention services for infants and toddlers (ages birth to three) until an amendment was added in 1986.

The pharmaceutical industry develops, produces, and markets drugs licensed for use as medications.

The inability to produce children. (Unified Medical Language Systems)

An inherited trait is one that is genetically determined. Inherited traits are passed from parent to offspring according to the rules of Mendelian genetics. Most traits are not strictly determined by genes, but rather are influenced by both genes and environment.

A committee that ensures that a clinical trial is ethical and that the rights of study participants are protected. All clinical trials in the U.S. must be approved by an IRB before they can begin. IRBs initially approve and periodically review clinical trials in order to protect participants’ rights.

A karyotype is an individual’s collection of chromosomes. The term also refers to a laboratory technique that produces an image of an individual’s chromosomes. The karyotype is used to look for abnormal numbers or structures of chromosomes.

The kidney is a body organ that filters blood for the secretion of urine and that regulates ion concentrations. (Unified Medical Language Systems)

According to U.S. federal legislation, disabilities involved in understanding or using language, manifested in impaired listening, thinking, talking, reading, writing, or arithmetic skills. Includes perceptual handicaps, brain injury, minimal brain dysfunction, and developmental aphasia. (Unified Medical Language Systems). Learning Disability (Ld) – a disorder that affects people’s ability to either interpret what they see and hear or to link information from different parts of the brain. It may also be referred to as a learning disorder or a learning difference.

A learning plan that provides the most possible time in the regular classroom setting.

Edema due to obstruction of lymph vessels or disorders of the lymph nodes. (Unified Medical Language Systems)

Lyonization is commonly known as X-inactivation. In mammals, males receive one copy of the X chromosome while females receive two copies. To prevent female cells from having twice as many gene products from the X chromosomes as males, one copy of the X chromosome in each female cell is inactivated. In placental mammals, the choice of which X chromosome is inactivated is random, whereas in marsupials it is always the paternal copy that is inactivated.

Mapping is the process of making a representative diagram cataloging the genes and other features of a chromosome and showing their relative locations. Cytogenetic maps are made using photomicrographs of chromosomes stained to reveal structural variations. Genetic maps use the idea of linkage to estimate the relative locations of genes. Physical maps, made using recombinant DNA (rDNA) technology, show the actual physical locations of landmarks along a chromosome.

A marker is a DNA sequence with a known physical location on a chromosome. Markers can help link an inherited disease with the responsible genes. DNA segments close to each other on a chromosome tend to be inherited together. Markers are used to track the inheritance of a nearby gene that has not yet been identified but whose approximate location is known. The marker itself may be a part of a gene or may have no known function.

Meiosis is the formation of egg and sperm cells. In sexually reproducing organisms, body cells are diploid, meaning they contain two sets of chromosomes (one set from each parent). To maintain this state, the egg and sperm that unite during fertilization must be haploid, meaning they each contain a single set of chromosomes. During meiosis, diploid cells undergo DNA replication, followed by two rounds of cell division, producing four haploid sex cells.

The metacarpals make up the “knuckles” of the hand.

Monosomy is the state of having a single copy of a chromosome pair instead of the usual two copies found in diploid cells. Monosomy can be partial if a portion of the second chromosome copy is present. Monosomy, or partial monosomy, is the cause of some human diseases such as Turner syndrome and Cri du Chat syndrome.

Mosaicism is an abnormal chromosome division resulting in two or more kinds of cells, each containing different numbers of chromosomes (chromosome mosaicism).

A mutation is a change in a DNA sequence. Mutations can result from DNA copying mistakes made during cell division, exposure to ionizing radiation, exposure to chemicals called mutagens, or infection by viruses. Germ line mutations occur in the eggs and sperm and can be passed on to offspring, while somatic mutations occur in body cells and are not passed on.

Malformed finger and toenail beds, often curved and lifted.

Newborn screening is testing performed on newborn babies to detect a wide variety of disorders. Typically, testing is performed on a blood sample obtained from a heel prick when the baby is two or three days old. In the United States, newborn screening is mandatory for several different genetic disorders, though the exact set of required tests differs from state to state.

A neuropsychological evaluation is a thorough assessment of an individual’s cognitive strenths and weaknesses that measure: brain damage; intellectual functioning; attention, concentration, and learning; verbal and visual memory; language functioning; academic skills; motor functioning; visual spatial and visual motor functioning; sensory perceptual functioning; executive functioning; conceptualization; planning and organizational skills; and processing speed.

The failure of homologous CHROMOSOMES or CHROMATIDS to segregate during MITOSIS or MEIOSIS with the result that one daughter cell has both of a pair of parental chromosomes or chromatids and the other has none. (Unified Medical Language System)

A neurological disorder which originates in the right hemisphere of the brain. Reception of nonverbal or performance-based information governed by this hemisphere is impaired in varying degrees, causing problems with visual-spatial, intuitive, organizational, evaluative, and holistic processing functions. (LD Online)

Oocyte Cryopreservation – a process in which a woman’s eggs are extracted, frozen and stored to future use. When the woman is ready to become pregnant, the eggs are fertilized externally then transferred to the uterus.

In biology, an organ (from the Latin “organum” meaning an instrument or tool) is a collection of tissues that structurally form a functional unit specialized to perform a particular function. Your heart, kidneys, and lungs are examples of organs.

Orphan Drug Act of 1983, a federal law that was written to encourage research into rare diseases and possible cures.

Ovarian Tissue Cryopreservation is the process of surgically removing part or all of an ovary and cryopreserving pieces of the tissue for future use. When ready to attempt pregnancy, the ovary is thawed and transplanted back into the woman’s body.

One of a pair of female reproductive glands in which the ova, or eggs, are formed. The ovaries are located in the pelvis, one on each side of the uterus.(National Cancer Instit.)

A patient is any recipient of healthcare services. wiki

Understanding the chain of clinical events that may cause a disease to progress

A pedigree is a genetic representation of a family tree that diagrams the inheritance of a trait or disease though several generations. The pedigree shows the relationships between family members and indicates which individuals express or silently carry the trait in question.

Controlled clinical studies conducted to evaluate the effectiveness of the drug for a particular indication or indications in patients with the disease or condition under study and to determine the common short-term side effects and risks.

Expanded controlled and uncontrolled trials after preliminary evidence suggesting effectiveness of the drug has been obtained, and are intended to gather additional information to evaluate the overall benefit-risk relationship of the drug and provide and adequate basis for physician labeling.

Post-marketing studies to delineate additional information including the drug’s risks, benefits, and optimal use.

A phenotype is an individual’s observable traits, such as height, eye color, and blood type. The genetic contribution to the phenotype is called the genotype. Some traits are largely determined by the genotype, while other traits are largely determined by environmental factors. (NHGRI)

Physical therapy (or physiotherapy), often abbreviated PT, is a health care profession. Physical therapy is concerned with identifying and maximizing quality of life and movement potential within the spheres of promotion, prevention, diagnosis, treatment/intervention and rehabilitation. This encompasses physical, psychological, emotional, and social well being. (wiki)

A physician is a health care provider who practices the profession of medicine, which is concerned with promoting, maintaining or restoring human health through the study, diagnosis, and treatment of disease, injury and other physical and mental impairments. They may focus their practice on certain disease categories, types of patients or methods of treatment – known as specialist medical practitioners – or assume responsibility for the provision of continuing and comprehensive medical care to individuals, families and communities – known as general practitioners.

A placebo is an inactive treatment, sometimes called a ‘sugar pill. ‘In fact, a placebo may be in a pill or tablet form. It may be an injection or a medical device. Whatever the form, placebos often look like the real medical treatment that is being studied except they do not contain the active medication.

A physical or emotional change, occurring after an inactive drug or treatment is taken that is not the result of any special property of that inactive drug or treatment.

Premature Ovarian Failure is a loss of normal function of the ovaries and requires replacement estrogen for normal development.

Developmental period during which secondary sex characteristics appear and individual becomes capable of sexual reproduction. (Unified Medical Language System)

Race is a fluid concept used to group people according to various factors including, ancestral background and social identity. Race is also used to group people that share a set of visible characteristics, such as skin color and facial features. Though these visible traits are influenced by genes, the vast majority of genetic variation exists within racial groups and not between them. Race is an ideology and for this reason, many scientists believe that race should be more accurately described as a social construct and not a biological one.

A method based on chance by which study participants are assigned to a treatment group. Randomization minimizes the differences among groups by equally distributing people with particular characteristics among all the trial arms.

In the United States, the Rare Disease Act of 2002 defines rare disease strictly according to prevalence, specifically “any disease or condition that affects less than 200,000 persons in the United States,” or about 1 in 1,500 people. According to the National Institutes of Health (NIH), there are almost 7,000 rare diseases affecting between 25 and 30 million Americans.

Recessive is a quality found in the relationship between two versions of a gene. Individuals receive one version of a gene, called an allele, from each parent. If the alleles are different, the dominant allele will be expressed, while the effect of the other allele, called recessive, is masked. In the case of a recessive genetic disorder, an individual must inherit two copies of the mutated allele in order for the disease to be present.

The reproductive cells in multicellular organisms. (Unified Medical Language Systems) A reproductive cell of the body. Germ cells are egg cells in females and sperm cells in males. (National Cancer Instit)

A Ring Chromosome occurs when a portion of a chromosome has broken off and formed a circle or ring. This can happen with or without loss of genetic material.

Risk, in the context of genetics, refers to the probability that an individual will be affected by a particular genetic disorder. Both genes and environment influence risk. An individual’s risk may be higher because they inherit genes that cause or increase susceptibility to a disorder. Other individuals may be at higher risk because they live or work in an environment that promotes the development of the disorder.

A sex chromosome is a type of chromosome that participates in sex determination. Humans and most other mammals have two sex chromosomes, the X and the Y. Females have two X chromosomes in their cells, while males have both X and a Y chromosomes in their cells. Egg cells all contain an X chromosome, while sperm cells contain an X or Y chromosome. This arrangement means that it is the male that determines the sex of the offspring when fertilization occurs.

Sex linked is a trait in which a gene is located on a sex chromosome. In humans, the term generally refers to traits that are influenced by genes on the X chromosome. This is because the X chromosome is large and contains many more genes than the smaller Y chromosome. In a sex-linked disease, it is usually males who are affected because they have a single copy of X chromosome that carries the mutation. In females, the effect of the mutation may be masked by the second healthy copy of the X chromosome.

A genetic or pathological condition that is characterized by short stature and undersize. Abnormal skeletal growth usually results in an adult who is significantly below the average height. (Unified Medical Language Systems)

Social Competence is the term used to describe how well or poorly a student performs in social situations.

Social skills are the specific reactions, responses, techniques and strategies that a student uses in social situations.

SPERM: Germ cell of the male sex. (Unified Medical Language Systems)

Natural height in an upright position. (Merriam Webster Medical Dictionary)

Strabismus is a disorder in which the two eyes do not line up in the same direction, and therefore do not look at the same object at the same time.

A syndrome is a collection of recognizable traits or abnormalities that tend to occur together and are associated with a specific disease.

An aggregate of cells with similar or identical specialized characteristics, contributing to the performance of a specific function. Tissues are parts of organs. Representative examples include epithelium, lymphoid tissue, and connective tissue. (Unified Medical Language System

A trait is a specific characteristic of an organism. Traits can be determined by genes or the environment, or more commonly by interactions between them. The genetic contribution to a trait is called the genotype. The outward expression of the genotype is called the phenotype.

Bringing scientific findings at a molecular or cellular level (usually basic research or “bench” research in a laboratory) into clinical application, or human studies.

Vitiligo (vit-ih-LIE-go):
A disease that causes the loss of skin color in blotches. The extent and rate of color loss from vitiligo is unpredictable. It can affect the skin on any part of your body. It may also affect hair, the inside of the mouth and even the eyes. Normally, the color of hair, skin and eyes is determined by melanin. Vitiligo occurs when the cells that produce melanin die or stop functioning. Vitiligo affects people of all skin types, but it may be more noticeable in people with darker skin. The condition is not life-threatening or contagious. It can be stressful or make you feel bad about yourself. Treatment for vitiligo may improve the appearance of the affected skin but does not cure the disease. – Mayo Clinic

The X chromosome is one of two sex chromosomes. Humans and most mammals have two sex chromosomes, the X and Y. Females have two X chromosomes in their cells, while males have X and Y chromosomes in their cells. Egg cells all contain an X chromosome, while sperm cells contain an X or a Y chromosome. This arrangement means that during fertilization, it is the male that determines the sex of the offspring.

X-linked is a trait where a gene is located on the X chromosome. Humans and other mammals have two sex chromosomes, the X and the Y. In an X-linked or sex linked disease, it is usually males that are affected because they have a single copy of the X chromosome that carries the mutation. In females, the effect of the mutation may be masked by the second healthy copy of the X chromosome.

The Y chromosome is one of two sex chromosomes. Humans and other mammals have two sex chromosomes, the X and the Y. Females have two X chromosomes in their cells, while males have X and Y chromosomes in their cells. Egg cells contain an X chromosome, while sperm cells contain an X or a Y chromosome. This arrangement means that during fertilization, it is the male that determines the sex of the offspring.

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