Medical Genetics

Name the inheritance pattern where only one allele is needed for the phenotype to be expressed
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Terms in this set (57)
What term refers to one of a pair of genes that appear at a particular locus and control the same characteristic?AlleleWhat is a gene said to be called if more than one allele occupies that gene's locus within a population?PolymorphicWhat is the term for the genetic composition of an individual?genotypeWhat is the term for an organism's observable and recognizable physical and biochemical traits?phenotypeWhat is it called when the two members of a gene pair are identical and code for the exact same gene?homozygousWhat is it called when the two members of a gene pair are different?heterozygousWhat term refers to the ability of a gene to express its function?gene penetranceWhat term refers to the manner in which the gene is expressed in the phenotype which can range from mild to severe?gene expressionWhat term is used when a single base pair is incorrect, so an incorrect amino acid is used in the protein?missense mutation; The resultant protein may be structurally unstable or may function normallyWhat term is used what a premature stop codon ends the amino acid chain?nonsense mutation; The resultant protein may be structurally unstable, or may degrade much quicker than usualWhat term is used when a deletion or insertion DOES NOT occur as a multiple of three (only a portion of a codon is deleted or inserted)frameshift mutation; Translation continues, if the protein is produced, it is abnormalWhat is the term for a deletion or insertion that occurs as a multiple of three?In-Frame mutation; a single amino acid is deleted or inserted. The protein may be structurally unstable or function normallyWhat is the term for a mutation that changes a single nucleotide, but does not change the amino acid createdsilent mutationWhat term is used to describe the result of nondisjunction during meiosis which causes there to be too many or too few chromosomes?Numerical chromosomal abnormalitiesName the three types of numerical chromosomal abnormalities?Monosomy = only one member of a chromosome pair Trisomy = Three chromosomes are present Polysomy = More than three chromosomes are presentWhat term is used to define alterations in chromosomal structure when a chromosome breaks and is followed by the rearrangement or deletion of chromosome parts?Structural chromosomal abnormalitiesName the two types of chromosomal structural abnormalitiesTranslocation = simultaneous breaks in 2 chromosomes from different pairs, with exchange of chromosome parts Deletions = deletions of whole chromosomal parts; Generally have severe effectsWhat term states that in some genetic disorders, the expression of the disease phenotype depends on whether the mutant allele was inherited from the mother or the father?Genomic imprinting; ex: deletion inherited from mother = Angelman syndrome deletion inherited from father = Prader-Willi syndromeWhat has the goal to map all of the genes that humans possess, using family linkage studies, gene dosage methods, and hybridization studies.The Human Genome ProjectThis was organized with the goal of developing a haplotype map of the genetic variations in human beings using single nucleotide polymorphisms (SNP's).The International HapMap projectWhat is used to identify people who carry one copy of a gene mutation that, when present in two copies, causes a genetic disorder?Carrier TestingWhat is used to detect changes in fetal genes and/or chromosomes before birth?Prenatal screeningWhat is performed just after birth to identify genetic disorders that can be treated early in life?Newborn ScreeningWhat is used to diagnose or rule-out a specific genetic or chromosomal condition? It is often used to confirm a suspected diagnosisdiagnostic testingWhat kind of diagnostic test captures the "whole picture" but does not pick up microdeletions or microduplications?Traditional KaryotypingWhich diagnostic test checks for the presence, absence, or rearrangement of a sequence on a chromosome? It also detects microdeletions and microduplicationsFISH (fluorescent in situ hybridization)Which diagnostic test amplifies DNA to detect the presence or absence of a sequence and measure its size?PCRWhich diagnostic test involves a needle being placed transabdominally under ultrasound guidance, and is used to obtain amniotic fluid that will be used for testing?Amniocentesis (15-20 weeks)Which diagnostic test involves cells being obtained via a needle transabdominally or transcervically?Chorionic villus sampling (CVS)Which diagnostic test uses umbilical cord blood for testing?Percutaneous umbilical cord sampling (cordocentesis)A chromosomal numerical disease. Trisomy 21: the presence of 3 chromosomes at position 21 Flat nose, face, upward slanting eyes, wide first to second toe gap intellectual impairment risk increased with maternal ageDown SyndromeAn autosomal recessive disease with a mutation in CFTR gene on chromosome 7 Pleiotropic effects: lungs have thickened mucus build up, sweat glands have elevated chloride and sodium More common in North European descent 1/25 to be a carrier for caucasians with no FHXCystic FibrosisAn autosomal dominant-mutation of FBN-I gene on chromosome 15. 75% of cases are from inherited mutations, 25% are from de novo mutations. The FBNI gene is essential for maintaining tissue elasticity in tendons, heart valves and blood vessels. Affects the ocular system, cardiovascular system, and skeletal system causing overgrowth of the long bones. Cardiovascular impairments are of major concern.Marfan SyndromeAn autosomal dominant mutation in the tumor suppressor gene that regulates cell differentiation and growth. Type one has a mutation of the gene on chromosome 17 and presents with Neurofibromas and cafe au-lait-spots. Type two has a mutation of a gene on chromosome 22. Other symptoms are visual impairments, disfigurement, and skeletal deformities (scoliosis)NeurofibromatosisAn autosomal recessive that is caused by the absence of an enzyme, which is caused by a mutation in the HEXA gene. Leads to accumulation of gangliosides in all organs Infants appear normal at birth then progress to muscle weakness, then followed by a rapid decline in mental function and the development of seizures. Death by 4-5 years of age. Ashkenazi Jewish ancestry is a risk.Tay-Sachs DiseaseAn X linked disorder with an expansion of the CGG trinucleotide repeat affecting the Fragile X Mental Retardation (FMR 1) gene on the X chromosome. Causes intellectual disability that is most prominent in males Presents with Elongated face, large mandible, large ears, large testesFragile X SyndromeAn autosomal recessive disorder. An inherited disorder that increases the levels of phenylalanine in the blood. A mutation on chromosome 12 which leads to the malfunction or complete absence of the PAH enzyme. Treated with a protein-restricted diet. More common in Caucasian and Native American ethnic groups, less common in African American, Hispanic, and Asians.Phenylketonuria (PKU)A chromosomal numerical disease (monosomal) Absence of all or a portion of female's X chromosome (45, XO) Short stature, wide chest, sterile. Also common to see neck webbing and other physical abnormalities normal intelligenceTurner SyndromeA chromosomal numerical disease. One or more extra X chromosomes (47, XXY) A nondisjunction in meiosis in one of the parents slightly lower IQ incomplete masculinization testes do not respond to stimulation in puberty, low testosterone, female distribution of fat, small testes, can not produce sperm, sparse facial or body hairKlinefelter SyndromeA trinucleotide repeat disorder of the huntington gene (HTT) on chromosome 4 Consists of an unstable CAG (glutamine) repeat Presents with cognitive decline, dimentia, depression. Chorea (involuntary jerky), and Dyskinesia (difficulty with voluntary movements)Huntington DiseaseX-linked recessive disease with a mutation in gene that encodes for protein dystrophin (usually maintains muscle integrity) Muscle atrophy that leads to premature death muscle weakness and decreased muscle mass wheelchair by 12 life expectancy 30Duchenne Muscular DystrophyAn autosomal dominant mutation that involves too much LDL cholesterol and total cholesterol because of absent or diminished LDLR. LDL deposits usually appear on back of neck and eyelids. Heterozygotes develop in 30-40s, Homozygotes develop severely in childhoodFamilial HyperlipidemiaAn autosomal recessive disorder with abnormal hemoglobin. It results from a mutation in the hemoglobin beta gene (HBB). It causes rigid, abnormal sickle-shaped cells that clump in areas of the body resulting in lack of blood flow to areas. Most prevalent in African Americans (1 in 365)Sickle Cell AnemiaX-linked recessive that leads to impaired ability to control blood clotting. It is caused by a mutation on the F8 gene which leads to a deficiency or defect in clotting factor VIII. Most commonly diagnosed severe bleeding disorder Mostly males are affectedHemophilia AA deletion of parental chromosome 15 (genomic imprinting) Intellectual disability with uncontrolled appetite Facies - small mouth, long head, almond eyesPrader-Willi SyndromeA deletion of maternal chromosome 15 (genomic imprinting) Is termed happy puppet syndrome. Is an intellectual disability with outbursts of laughter, speech problems, ataxia, and seizuresAngelman SyndromeA Chromosomal structural disease. Involves a deletion of a small piece of chromosome 22. Has an autosomal dominant inheritance pattern. Common effects include: Developmental delay, congenital heart defects, cleft lip/palate. abnormal facies (underdeveloped chin, low-set ears, wide-set eyes, or a narrow groove in the upper lip)DiGeorge Syndrome