Genetic Disorders PART ONE: Detecting Genetic Disorders Amniocentesis Chorionic villus sampling Karyotype Triple Screen Blood Test
Amniocentesis A technique for determining genetic abnormalities in a fetus by the presence of certain chemicals or defective fetal cells in the amniotic fluid, obtained by aspiration from a needle inserted into the uterus.
CVS sample sample of embryonic cells taken for chorionic villus (placenta) can be done earlier than amniocentesis and results yielded sooner A method of organizing the chromosomes of a cell in relation to number, size, and type. Taken during METAPHASE of Mitosis. Karyotype
Karyotype Normal Male 46 XY
Normal Female 46 XX Female with Down Syndrome 47 XX +21
PART TWO: Gene Mutations Point mutations Changes in 1 or a few base pairs in a single gene Substitutions Frameshift mutations Base-pair insertions or deletions; alters the reading frame of triplets THE FAT CAT ATE THF ATC ATA TE. Inherited Genetic Disorders Autosomal Recessive Must inherit two recessive alleles, one from each parent. Parent s s are usually CARRIERS of the disorder Autosomal Dominant Inherit one allele Sex-Linked Disorders Usually recessive, inherited on X-chromosomeX More common in males
AUTOSOMAL RECESSIVE PKU Albinism Tay-Sachs Cystic Fibrosis Sickle Cell Anemia Tay-Sachs Autosomal recessive Degeneration of nervous system No enzyme to break down lipids in brain cells, so they swell and die (death by age 5) - Lethal High incidence in Ashkenazie Jews Blood test available to potential parents
Albinism Lack of pigmentation in skin, hair, eyes Inability to make melanin Autosomal recessive PKU Phenylketonuria Autosomal Recessive Lack enzyme to convert phenylalanine to tyrosine Buildup of phenylalanine can cause retardation Test babies at birth Special diet for phenylketonurics (low protein)
Sickle Cell Anemia Abnormal hemoglobin 1 aa substitution causes abnormality (point mutation) deletion of only THREE nucleotides on chromosome 7 Codominance (carrier) Low oxygen RBC will become crescent shape Cystic Fibrosis Cystic Fibrosis,, incurable hereditary disorder that causes the body to secrete an abnormally thick, sticky mucus that clogs the pancreas and the lungs,, leading to problems with breathing and digestion, infection, and ultimately, death. Common among Caucasians One of the most common fatal genetic disorders in the United States Lethal
AUTOSOMAL DOMINANT Huntington s s Disorder Marfan Syndrome Achondroplasia Marfan Syndrome Autosomal Dominant Connective tissue defect Tall, thin, long arms and legs Enlarged aorta
Achondroplasia Autosomal Dominant Defects in growth of long bones Form of dwarfism Short arms and legs but torso of normal size, large head compared to body Huntington s s Disease Autosomal Dominant Disorder (lethal) CNS problem, degenerative brain disorder Dementia Impaired memory Asymptomatic until later in life
SEX-LINKED DISORDERS Gene loci on a sex-linked chromosome Genes for many sex-linked traits, unrelated to gender, are found on the X chromosome Follow Mendelian Laws of Inheritance May be either dominant or recessive Hemophilia (recessive) Duchenne Muscular Dystrophy (recessive) Colorblindness (recessive) Hemophilia Sex-linked recessive disorder Lack of protein necessary for normal blood clotting
Duchenne Muscular Dystrophy Sex-linked recessive disorder Absence of muscle protein dystrophin Progressive muscle deterioration and loss of coordination most die by age of 20 Colorblindness Sex-linked recessive Inability to distinguish colors
PART THREE: NON-DISJUNCTION Chromosomes fail to separate properly - can occur during meiosis I (all cells affected) or meiosis II (half cells affected) Aneuploidy - having an abnormal chromosome number Trisomic/Trisomy - having 3 chromosomes 2n+1 Monosomic - having 1 chromosome 2n-1 Polyploidy - having move than 2 sets of chromosomes Triploidy - (3n) Tetraploidy - (4n) common in plants usually lethal in animals and humans
NONDISJUNTION DISORDERS Down s s Syndrome - Trisomy 21 Edward s s Syndrome - Trisomy 18 Patau s s Syndrome - Trisomy 13 Turner s s Syndrome - X0 Klinefelter s s Syndrome - XXY Super Male - XYY Super Female - XXX Down s s Syndrome Characteristic facial features, low mental ability, stocky build, sometimes heart defects. Extra copy of chromosome #21
Edward s s Syndrome Trisomy 18 Motor and mental retardation Congenital heart disease Often dies in infancy Patau s s Syndrome Trisomy 13 Physical abnormalities cleft palate, polydactaly, microcephaly
Turner Syndrome XO Female missing one X chromosome short stature wide neck with extra skin folds underdevelopment of sex characteristics may lead to sterility non-disjunction of sex chromosomes Klinefelter s s Syndrome XXY XXY male with extra X chromosome poor sexual development, may be sterile subnormal mental ability other forms are XXYY, XXXY, XXXXY (additional X s increase the severity of phenotypes and mental retardation)
Super Male XYY Male with extra Y chromosome Very tall, can show violent behavior Prone to acne Impaired fertility Mentally normal PART FOUR: Chromosomal Abnormalities
Short Arm of # 5 Cri du- chat Cat-like cry Severe physical and mental abnormalities nonlethal