Gene Counseling L20

Gene Counseling L20 - An overview of Human Genetics &...

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An overview of Human Genetics Ushta Davar Canteenwalla, MS, CGC Columbia University Medical Center Center for Prenatal Pediatrics Morgan Stanley Children’s Hospital of New-York Presbyterian
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Overview Genetics Basics Mode of Inheritance Genetic Counseling examples Prenatal Screening Genetic Counseling examples Types of Genetic Counseling Prenatal Pediatric Adult Cancer Genetic Counseling as a Career Questions
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The Basics: Chromosomes, DNA, and Genes Cell Nucleus Chromosomes Gene Protein
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Chromosomes Male Female 46 Chromosomes ~30,000-50,000 genes Each chromosome contains 100s to 1000s of genes
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How chromosomes and genes are passed on Each egg cell has 23 chromosomes Each sperm cell has 23 chromosomes Conception 23 + 23 = 46
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Chromosome abnormalities Down Syndrome results from an extra copy of chromosome number 21
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Other Chromosome abnormalities Other types of chromosome abnormalities include: Missing chromosomes Translocations Insertions Deletions/Duplications Inversions Marker chromosomes
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Single Gene Inheritance 2 copies of every chromosome 2 copies of every gene (1 from mom and one from dad) Dad Mom Child
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We are all mutants! We each have ~30,000 genes. Gene changes that stop a gene from working as it should are called mutations. Each person probably carries a handful of mutations. Most of us do not know what mutations we carry because the working copy of the gene compensates for the non-working one. Working Gene with Gene Mutation
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Autosomal Dominant: Achondroplasia 1 mutation = disease Short stature-short arms and legs Large head size Characteristic facial features Normal intelligence and life span (Increased risk for death in infancy from compression of the spinal cord and/or upper airway obstruction) (Assortative mating) 2 mutations = lethal
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FGFR3 gene Chromosome 4 Mother Father with Achondroplasia working copy Non-working copy (mutation) ½ (50%) Unaffected A person with achondroplasia whose parents are of normal stature could also have a new mutation in FGFR3 ACHONDROPLASIA ½ (50%)
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Autosomal Recessive: Cystic Fibrosis 2 mutations = disease Incidence 1:2500 Lung disease-airway infection, inflammation and damage Pancreatic disease-enzyme insufficiency and malabsorption. Failure to thrive. Intestinal obstruction at birth 15-20% Infertility in males (can be isolated CBAVD) Salty sweat Life expectancy 40s
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CFTR gene Chromosome 7 Mother Father ½ (50%) ¼ (25%) ¼ (25%) Carrier Unaffected CYSTIC FIBROSIS Non-Carrier Unaffected working copy Non-working copy (mutation)
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X-linked inheritance Males 1 copy of X chr genes (from mom only) Females 2 copies of every gene on the X chr
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X linked Recessive: Hemophilia A Males 1 mutation = disease Females 1 mutation = carrier Incidence: 1 in 10,000 Prolonged oozing after injuries, tooth extractions, or surgery
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This note was uploaded on 10/27/2010 for the course BIOL 125 taught by Professor Klein during the Spring '10 term at CUNY Hunter.

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Gene Counseling L20 - An overview of Human Genetics &...

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