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Proteus Syndrome Neurofibromatosis Angelman Holoprosencephaly Genetic Disorders Cystic Fibrosis Down’s Syndrome When things don’t go right Marfan Tay-Sachs Huntington’s Disease Progeria Karyotype - a picture of chromosome pairs It shows us chromosomes! 1. Homologous chromosomes 2. Autosomal Chromosomes 3. Sex chromosomes Pairing up chromosomes! 1. Size 2. Gene bands 3. Location of centromere Humans have: 22 pairs of autosomes 1 pair of sex chromosomes tells gender, total = 23 pairs or 46 chromosomes. • Chromosomes are made up of _____ genes which are made up of ____ DNA & ______ protein • Organisms’ chromosomes come in Homologous _______________ pairs (one from mom, one from dad) • Homologous pairs are evident during meiosis ______, where they then separate. • The location of a gene on the chromosome is called its ______ locus • Traits can be expressed as different ________ alleles at the gene locus Allele for blue eyes (b) Gene loci for eye color Homologous chromosomes Allele for brown eyes (B) Crossing Over • During Prophase 1 – Homologous chromosomes pair up (synapsis) – Tetrads of 4 sister chromatids intertwine – At the chiasma - homologous pairs swap pieces of chromosome – crossing over results in more genetic diversity chiasma tetrad synapsis Chromosomal Disorders due to Nondisjunction • Homologous pairs are supposed to separate during anaphase I of Meiosis • Then their sister chromatids are supposed to separate during anaphase II of Meiosis • The number of chromosomes in gametes should be N (the haploid number) Cell A • Which is the most devastating? Cell B How many viable sperm for Cell A? cell B? Sex Chromosome Disorders due to Nondisjunction Autosomal Disorders due to Nondisjunction Distinguish between: Autosomal Disorders: a. Cystic fibrosis b. Tay-Sachs Disease c. Sickle Cell Anemia Sex-Linked Disorders: a. Color-blindness b. Duchenne Muscular Dystrophy c. Hemophilia Cystic Fibrosis • The most common inherited disease among Caucasians 1 out of 25 is a carrier. • Autosomal recessive (7q31.2) In one form of CF, a mutation in the DNA causes a binding site on the CFTR The Normal CFTR Protein in the Lungs: protein to change shape, and the ATP will not bind. Using active transport, a Cl- ion is pumped ATP will not bind at the mutated site. across the cell membrane of normal lung Cl- can not leave the cell. A thick, cells through a Cl- ion channel. stringy mucus builds up on the outside The Cl- attracts water, which moistens the lung cell of the lung cell membrane. membrane, helping to produce a thin layer of The thick mucus provides a home to mucus. bacteria which cause deadly infections. Cl- P Tay-Sachs Disease Warren Tay - Opthalmologist, who described the cherry-red spot on the retina Bernard Sachs - Neurologist, who first described the changes in the brain A rare autosomal recessive disorder of the HEX A gene on the long arm (q) of chromosome 15 between position 23 and 24 Over 100 mutations have been identified in the HEX A gene - single base insertions, deletions, missense mutations, splice phase mutations where introns are not properly excised, etc. which alters the gene’s normal protein production of a lysosomal enzyme. A progressive deterioration of nerve cells due to a build up of gangliosides in the brain’s nerve cells. Mental and physical deterioration begins around six months of age, often leading to death by age four. Other Chromosome 15 Syndromes Marfan Syndrome An autosomal dominant disorder caused by a mutation in the FBN1 gene which produces fibrilin-1. Fibrillin-1 forms fibers in connective tissue and is supposed to bind to TGF-ß (a growth factor), keeping it sequestered. Without adequate Fibrillin-1, heart, blood vessels, bones, joints, and eyes are compromised. Prader-willi Syndrome Rare genetic disease where 7 genes on the paternal chromosome 15 are deleted or silenced. Extreme and insatiable appetite- thus often become obese, narrow at the temple, poor muscle tone, cognitively IQ’s tend to range 35 - 85 Angelmann Syndrome Rare genetic disease where genes on the maternal chromosome 15 are deleted or silenced. Seizures, jerky movements (hand-flapping), happy laughing, smiling demeanor, severe intellectual and developmental disabilities. A. Sickle Cell Anemia http://www.pbs.org/wgbh/evolution/library/01/2/l_012_02.html An autosomal recessive disorder caused by a point mutation (substitution) on Chromosome 11 at the Beta Globin Gene, which is responsible for making hemoglobin, a complex protein structure in red blood cells - the iron-rich oxygen carrying molecule of the circulatory system in all vertebrates. Normal Red Blood Cells Sickle Cells get Sickle Cells trapped in capillaries A mutation occurs in the Beta Globin Gene and: The codon CTT is changed to CAT, so instead of making Glu (glutamic acid) --> it makes Val (valine) 1 amino acid change of 146 amino acids = Sickle Cell Anemia Heterozygous for sickle cell makes a person immune to Malaria because the presence of the protozoan (transported by the mosquito) causes the defective red blood cell to rupture before the protozoan can reproduce. C. Colorblindness The Gene for Red Green Vision is carried on the X Chromosome. It is an X-linked recessive disorder. One mutation causes Red-Green colorblindness--found almost exclusively in males. Women have an extra X chromosome, called a Barr Body, That can serve as a “back up” if the first is faulty ROYGBIV What a person with normal color vision sees. http://colorvisiontesting.com/ How does the world look to a color blind person? YGBIV What a person with red green colorblindness sees. Duchenne Muscular Dystrophy A recessive, X-linked disorder caused by a mutation in the dystrophin gene where exons 45 to 54 the short arm (p) of the X chromosome at Xp21.2 are deleted. Dystrophin is an important structural component within muscle tissue providing structural stability, without sufficient amounts, leads to muscle degeneration and eventually death. Hemophilia A recessive, X-linked disorder caused by a mutation in the F8 gene (Classic Hemophilia A Factor VIII deficiency) or F9 gene (Christmas Disease or Factor IX deficiency) where normal clotting proteins are either missing, lacking or ineffective in coagulation to seal damaged blood vessels and prevent excessive loss of blood.