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| 1.1 A Look Ahead 1. Genetics is a branch of biology concerned with heredity and variation. 2. Genes are the unit of inheritance and are composed of DNA. 3. DNA sequence data generated by the human genome project will lead to genetic tests that will help to identify inherited disease susceptibilities and predict future health. 4. The availability of DNA microarray technology is revolutionizing the development of DNA testing.1.2 From Genes to Genomes 1. The effects of genes are noticeable at the molecular, cellular, family, and population levels. 2. Genes are DNA sequences that instruct cells to produce particular proteins, which in turn determine traits. 3. Genes can exist in more than one form and the variants of a gene arise by mutation. 4. An allele is a variant of a gene that alters its expression in a detectable way. Alleles can be dominant or recessive. 5. A polymorphism is a particular sequence of DNA that varies in one percent or more of the population. 6. Single nucleotide polymorphisms are single base pair sites that differ among individuals. 7. Chromosomes consist of genes and associated proteins. 8. The human genome consists of 22 pairs of autosomes and one pair of sex chromosomes. 9. A karyotype is the photographic catalog of the human chromosomes. 10. Specialized cells and tissues arise by differentiation from the stem cells of the early embryo. 11. Pedigree diagrams enable recessive and dominant traits to be followed through multiple generations of a family. 12. A gene pool is the collection of alleles in a population. 13. Comparative genomics is leading to a more detailed and subtle understanding of evolutionary relationships among species. 1.3 Genes Do Not Usually Function Alone 1. Mendelian traits are determined by single genes. 2. Mendelian disorders are generally rare. 3. Multifactorial traits are determined by multiple genes and environmental effects. 4. Many common illnesses have a multifactorial basis. 5. Genetic determinism is the point of view that the environment has little effect on gene expression. 1.4 Geneticists Use Statistics to Represent Risks 1. Genetic counselors apply knowledge of mode of inheritance and pedigrees to determine probability of inheriting a particular trait or condition. 2. The risk of inheriting a trait or condition can be expressed as absolute or relative figures. 3. Risk figures are based on population level observations (empiric), Mendel's laws, or are "modified" to account for single genes as well as environmental and family background information. 1.5 Applications of GeneticsEstablishing Identity-From Forensics to Rewriting History 1. Genetic tools are used in diverse areas such as forensics, establishing paternity, agriculture, and health care. 2. DNA typing can exclude an individual from being biologically related to someone else or from having committed a crime.Health Care 1. Genetic diseases differ from infectious diseases in that the recurrence risks are predictable, pre-symptomatic diagnosis using genetic testing is possible, and characteristic frequencies are observed in different populations. 2. After identifying underlying genetic abnormalities (mutations), gene therapy can be used to treat and possibly prevent certain genetic disorders. Agriculture 1. Agriculture, both traditional and biotechnological, applies genetic principles. 2. Traditional agriculture involves controlled breeding to select now combinations of inherited traits. 3. Genetically modified (GM) foods have genes introduced from the genomes of other organisms. |