Presentation on theme: "Uses of Genomic Information in the Diagnosis of Disease"— Presentation transcript:
1Uses of Genomic Information in the Diagnosis of Disease
2What is Genomics?Genetics is the study of inheritance or the way traits are passed down from one generation to anotherGenes have the information to make proteins which direct cell activities and functions and influence traits such as hair and eye colorApproximately 30,000 genes in the human DNAGenomics is a newer term describing the study of all of a person’s genes and the interactions of those genes with each other and with the environment
3Importance of Genomics Genomics have a role in 9 of the 10 leading causes of death in the USAll humans have 99.9% identical genetic makeupThe remaining 0.1% difference may provide useful information about diseasesThe goal of genetics is to show why some people get sick from certain infections and environmental changes while others do not.
4Human Genome Project (HGP) A 13 year project where all of the genes in the human DNA were discoveredDetermined the sequences of approximately 3 billion chemical base pairs that make up the human DNACompleted in 2003 by the U.S. Department of Energy and the National Institutes of Health with help from many other countries including Japan, Germany and France
5What are genetic disorders? A disease caused in whole or in part by a variation or mutation of a geneResearchers are discovering that nearly all diseases have a genetic component
6What are genetic disorders? Some are caused by a mutation in the gene or group of genes in a person’s cellsThese may be random or from environmental exposure such as cigarette smokeOthers are hereditarythe mutated gene is passed down through the familyMost are multifactorial inheritance disorders-caused by a combination of small variations in genes, often connected with environmental factors
7Three Categories of Genetic Disorders 1) Single Gene DisordersCaused by a mutation in a single gene. The mutation may be present on one or both chromosomesSuch as Sickle cell disease, cystic fibrosis and Tay-Sachs2) Chromosome Disorders-caused by an excess or deficiency of genes on the chromosomes or structural changes within chromosomes-Down syndrome
8Three Categories of Genetic Disorders 3) Multifactorial Inheritance Disorders-caused by a combination of small variations of genes-heart disease, most cancers, and behavioral disorders such as alcoholism, obesity, mental illness, and Alzheimer’s disease are examples
9Genetic Testing Today more than 900 genetic tests are available. There are also suseptability tests which can determine an estimated risk for developing the diseaseList of common tests available:Database for the entire human genome
10Genetic Testing: How it Works Scientists scan a patient’s DNA for mutated sequencesThe DNA sample can come from any tissue including bloodFor some tests, probes, short pieces of DNA, are designed with sequences complimentary to the mutated sequence.The probe will seek its compliment among the base pairs and will bind to it and flag the mutationOther tests compare the bases in a patient’s gene to that of a normal gene
11Genetic Tests: Types Available Carrier Screening--Identifies unaffected individuals who carry one copy of the gene that needs two to express the diseasePreimplantation genetic diagnosisembryo from in vitro fertilization is tested before implanted in the uterusPrenatal Diagnostic TestingNewborn screening
12Prenatal diagnostic testing: What tests show Neural tube defectsBirth defects of the brain or spinal cordChromosomal AbnormalitiesIndicated by abnormal amounts of substances in the mother’s blood such as alfa-feto protein and estriolMost fetuses with these abnormalities die before birth
13Prenatal diagnostic testing: Types of tests UltrasonographyPerformed before other tests to detect obvious structural defects in the fetusChorionic Villus SamplingA doctor removes a small sample of the chorionic villi, which are small projections that make up part of the placentaCan be done between weeks of pregnancy so the diagnosis is earlier
14Prenatal diagnostic testing: Types of tests AmniocentesisOne of the most common prenatal testsA sample of amniotic fluid is removed and tested for alpha-fetoprotein level
16Epidemiology Human Genome Epidemiology The use of the human genome to study vast groups of peopleHGDPHuman Genome Diversity ProjectUses genomics to study different diseases affected by a person’s genes among ethnic groups
17Benefits of Genetic Testing Some tests can clarify a diagnosis for a more concise treatmentOther tests can prevent families from having children with devastating diseases
18Disadvantages of Genetic Testing Commercialized gene tests for adult onset disorders and some cancersFor presymptomatic people at high risk because of family medical historyThey only give a probability for developing the disorderPeople who carry the mutation may never develop the disorderPossibility for errors due to contamination or misidentificationCost can range from hundreds to thousands of dollars
19Gene TherapyGene therapy is a technique for correcting faulty genes which cause diseasesGenes are specific sequences of bases that encode instructions on how to make proteins which perform most cellular functions and make up the majority of the cellular structureWhen defective genes encode proteins unable to perform properly, genetic disorders can occur
20Methods of Gene Therapy A normal gene may be inserted into a non-specific location within the genome to replace a faulty gene (most common method)The abnormal gene can be swapped for a normal gene through Homologous Recombination.
21Homologous Recombination The process where two homologous chromosomes exchange a distal portion of their DNA during prophase 1 of meiosis. The two homologous chromosomes break and reconnect to the different end piece. If they break at the same place in the base pair sequence, the result is an exchange of genes called genetic recombination. It could be as often as several times per meiosis.
22Methods of Gene Therapy The abnormal gene can be repaired through Selective Reverse Mutation, returning the gene to its normal functionThe regulation of a gene, the degree to which it is turned on or off can be altered