Text of Human Genetics Introduction. Human genetics: Why? Determine genotypic basis of variant...
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Human Genetics Introduction
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Human genetics: Why? Determine genotypic basis of variant phenotypes to facilitate: Understanding biological basis of human genetic diversity Prenatal diagnosis Predictive testing Development of intelligent therapies Correction of genetic defects Human Identification for forensics, evolution
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Class Objectives 1.To provide an understanding of the basic principles of genetics. 2.To provide an understanding of the genetic basis of human disease and current approaches to treatment and prevention of genetic disorders. 3.To relate the study of human genetics to major advances in molecular genetics and biotechnology. 4.To provide an awareness of the interaction between genetic and environmental factors underlying birth defects and the development of human disease.
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Class Objectives 5.To relate human genetics to current issues in genetic screening, genetic counseling and genetic engineering. 6.To provide an awareness of the relationship of the individual genome to the genetic makeup of the human population and its ramifications to human diversity. 7.To provide a learning opportunity for students enrolled in Biological and Health Sciences applicable to career areas including biomedical technology, pre-medical, secondary education, special education, and nursing.
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Course Topics Cell Biology and Biochemistry Review Classical Mendelian Genetics DNA and Chromosomes Molecular Genetics Immunity and Cancer Genetic Counseling, Gene Therapy, Ethics Population/Evolutionary Genetics
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Grading Lab Work (Lab participation and reports, Lab questions,)35% Lecture quizzes 30% Final Exam20% Family Tree10% Problem sets 10% Class participation 5%
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1. DNA 2. Gene 4. Genome 5. Individual 3. Chromosome 7. Population 6. Family (pedigree) Cell
What is Genetics? Genetics is the study of heredity and its variation. Human genetics: What's different? Nothing (in principle) Unmatched by other organisms for phenotypic complexity
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Genes are DNA Genes are the basic unit of inheritance. Genes are composed of DNA (deoxyribonucleic acid) Genes direct the formation of proteins. Different versions of the same gene are called alleles. Alleles result from the process called mutation. All genes are nucleic acids (RNA and DNA) but not all nucleic acids are genes.
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Somatic versus Germline Cells Somatic cells comprise the majority of an individuals body. During development distinct types of cells make proteins using different subsets of genes. Germline cells within the testis or ovary produce gametes (sperm or ovum) Germline cells retain the ability to form all of the types of cells, both germline and somatic cells. Together somatic cells and germline cells comprise the entire body of an individual.
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The complete set of genetic information characteristic of the organism. The genome includes: All of the genes present in an organism and Other DNA sequences that do not encode genes Genome
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Consists of 3 billion base pairs of DNA Includes 28,000 to 34,000 genes Is organized as 23 pairs of chromosomes The Human Genome
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Individuals Individuals carry two alleles of each gene. Genotype is the combination of alleles that an individual possesses. Phenotype is the visible trait that results from a particular genotype.
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Inheritance of traits can be observed in families. A pedigree indicates the structure of a family schematically. Family
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A population is a group of interbreeding individuals who possess a particular collection of alleles or gene pool. Population
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Species Comparisons Comparison of DNA sequences indicates the amount of similarity between two species. 98% of human DNA sequences are shared with chimpanzee. Many genes present in humans are also present in mice, fish, fruit flies, yeast, and bacteria.
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Humans are very similar On average, two random people share the same DNA sequence in 99.9% of their genome. Studies of variation indicate humans arose in Africa and migrated across the globe with relatively little change.
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Humans are also very different On average two random people differ at 3 million base pairs (approximately one nucleotide of every thousand). A few genes can have a big impact on appearance.
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Understanding the relationship between genotype and phenotype 1)Experimental organisms: manipulate genotype, determine phenotype 2) Humans: assay phenotypes, determine genotype (statistics)
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How are traits determined? Traits can be determined predominantly by one gene. Mendelian traits result from variation in alleles of one gene. Traits can be determined by multiple genes. Polygenic traits result from variation in several genes. Traits can be determined by genes and environment. Multifactorial traits result from effects of one or more genes and the environment.
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Genetic Risk Absolute riskthe probability that an individual will develop a condition or trait Relative riskthe likelihood that an individual from one group will develop a condition in comparison to another group (usually the general population) Empiric riskrisk determined by observing incidence of a trait in the population Risk factora situation that alters incidence of a disease (or trait)
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Brief History
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Human Genome Decoded 2001
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How Genetic Diseases Differ from Other Diseases One can predict recurrence risk in other family members Predictive testing is possible Different populations have different characteristic frequencies Correction of the underlying genetic defect may be possible
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Our First Assignment Developing a family history according to recommendations of the American Society of Human Genetics. Building a pedigree of some trait using that pedigree to consider whether it could have a genetic component.
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Unaffected Male Unaffected Female Affected male Affected female Parents Offspring Pedigree Analysis
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Human Pedigree Symbols
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Disease No disease Assuming pedigrees like this are available (they never are), how do you find linked molecular markers (and clone the gene)? 1)Obtain polymorphic markers for loci that "span the genome" 2)Identify closely linked flanking markers 3)Narrow non-recombinant interval and test candidates for causality An Ideal(ized) Pedigree
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Royal Pedigree of Porphyria
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Geneology DNA Testing http://www.familytreedna.com/
