Genetic Abnormalities
How they occur Sample Collection of Genetic
Disorders
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Genes and Disease
National Center for Biotechnology Information
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A division of the National Library of Medicine at the National Institute of Health Research & collaborative data collection and storage for researchers to better understand the link to genetics with health and disease
Chromosome Map
Genetic Testing
Genetic Counseling Pedigree Analysis Blood test for proteins Phenotype analysis Fetal Testing Karyotype Amniocentesis Chorionic villus sampling (CVS) Newborn Testing
Chromosomal Errors: Problems in Meiosis
Nondisjunction:
Aneuploidy:
• Monosomy • Trisomy • Polyploidy
Down’s Syndrome
Extra chromosome 21
(autosomal) Trisomy, from nondisjuntion Short stature; characteristic facial features; mental ability is variable; often problems with the circulatory system
Figure 5.15
Klinefelter’s Syndrome
Extra sex chromosome
(XXY) Trisomy,from nondisjuntion Infertile male (extra X interferes with meiosis); feminine physical traits; below average intelligence; taller than average
Turner’s Syndrome
One less sex chromosome (XO)
Monosomy, resulting from nondisjuntion
Infertile female; sex organs don’t fully
develop Typically below ave. height; normal intelligence
Chromosomal errors: Alterations of chromosomal structure
Deletion Inversion
Base Substitution
Duplication Translocation Repeats
Cystic Fibrosis
3 base-pair deletion in sequence on
chromosome 7 Autosomal Recessive Inheritance Produces a defective chloride ion membrane protein an increase of salt (NaCl) in bodily secretions body produces a thick, sticky mucus that clogs the lungs causing infection blocks the pancreas stopping digestive enzymes from reaching the intestines for food digestion
Phenylketonuria (PKU)
Located on chromosome 12
Autosomal Recessive Inheritance
Failure to convert phenylalanine to tyrosine
(lacks phenylalanine hydrolyase) toxic levels in the blood mental retardation Treatment- avoidance of foods with phenylalanine
Albinism
Located on chromosome 11- deletion
Autosomal Recessive Inheritance
Tyrosinase deficiency Blocks pathway to produce melanin
Sickle Cell Anemia
Located on chromosome 11
Base substitution
single amino acid substitution
Autosomal Recessive Inheritance
Produces mutated form of hemoglobin
Blocks capillaries localized hypoxemia
Achondroplasia
Located on chromosome 4
Autosomal Dominant Inheritance
Homozygous dominant is lethal disease
Form of dwarfism
Figure 14.15
Huntington Disease
Located on chromosome 4
Repeat
Autosomal Dominant Inheritance Build up of toxic proteins on the brain
nervous system breaks down Adult onset, usually during or after reproductive years
Red-Green Colorblindness
Located on X
chromosome Deletions due to unequal crossing over Sex-linked Recessive Inheritance A range of phenotypes, depending upon the type of deletion
http://www.thetech.org/genetics/images/ask/colorblind.jpg
http://www.coolopticalillusions.com/optical_illusions_pictures_3/color_blindness_test.htm
Hemophilia
Located on X chromosome
Base substitution
Sex-linked Recessive Inheritance Inability to make one/more of the clotting
factors
bruising, prolonged bleeding, anemia
Duchenne’s Muscular Dystrophy
Located on X chromosome- large gene
high mutation rate Sex-linked Recessive Inheritance Makes defective protein, causing muscle to weaken
Cri-du-Chat
Deletion of half of chromosome 5
“cry of the cat”- characteristic of infants
Mental retardation; slow growth; small head;
finger webbing Cri-du-Chat YouTube video
Fragile X Syndrome
Sex-linked Dominant Inheritance repeat sequence CGG
Normal repeats (Variable Number Tandem Repeat- VNTR) = 5-50 Premutation = 50-200 repeats Full Mutation = over 230 repeats!! Leads to FMR1 gene not expressed- no FMRP
Plays a role in synaptic connections of nerve cells
Not always expressed due to x-inactivation
Most common cause of mental retardation Distinctive physical appearance Long face, large ears
Angelman & Prader Willi Syndromes
Deletions on chromosome 15 Genomic imprinting If from father- Prader Willi Syndrome
characterized by obesity low muscle tone, cognitive disabilities, & incomplete development severe mental retardation development, speech, movement)
If from mother- Angelman Syndrome
unusual facial appearance
apparent happy demeanor
muscular abnormalities
hand flapping
Angelman vs Prader Willi Syndromes