CHAPTER 1: An Overview of Genetics
- Genetics is a young science. Genetics is the study of the biological/biochemical basis of inheritance.
- Classical genetics begins by studying Mendel's research, and provides a starting point for our study of genetics.
- Until the early1900's, Mendel's studies failed to be understood.
- The year1900 marked the beginning of modern genetics.
- In just a century, we have arrived at the point where we have the ability to manipulate DNA – the substance of inheritance – to alter life forms. And, we have sequenced the entire human genome.
- One of the important keys to this startling accomplishment was that both success and failure contributed to progress.
GENETICS IMPACT TODAY
- CNN, NBC, Time Magazine and other news media report almost daily on genetically-related news; like if O.J.’s blood was at the scene of the crime, the genetic basis for heart disease, methods for treatment of AIDS, cloning of mammals including humans, and the "flavr savr" tomato, which is a plant modified to delay rotting.
- In 1902 Sir Archibald Garrod was first to discover a genetic link to a disease: alkaptonuria. This disease causes homogentisic acid to accumulate to toxic levels. Homogentisic acid is an intermediate to the breakdown of the amino acid, phenylalanine.
- Accumulation of homogentisic acid is due to a defective or absent enzyme that normally converts this intermediate.
- The homogentisic acid oxidizes in the air turning the afflicted person's urine black.
- Black urine is an indicator of the disease.
- Inheritance of this disease followed Mendelian inheritance patterns.
- Therefore, Garrod was the first person to associate a gene with an enzyme; and, was the first to discover an Inherited disease.
- He concluded this after long deliberation and consolation with other scientist.
- Many other diseases have been found to be caused or influenced by defective genes.
- Even cancer is a genetically based disease. See Figure 1.3.
- Knowledge can be the starting point for formulating a strategy for treatment.
- Knowledge creates controversy as well.
- Assays for disease propensity could make it difficult for some (actually many) to get full medical insurance coverage.
- From Mendel’s principles to the application of the most modern molecular technologies, genetics has impacted all of agriculture.
- New hybrid corn plants, genetically selected dairy herds, and tomatoes that stay fresh longer are the fruits of the knowledge of genetics.
- Most progress in genetics has been made in the last 100 years, although plant and animal selection has been practiced for thousands of years. See Figure 1.4.
- Recently, cloning of adult mammals, including humans, has been achieved.
- Assays for all sorts of genetic diseases have been developed.
- Mapping and patenting regions of human chromosomes has been completed.
- Many controversies center on genetic topics.
- Be sure to read about Lysenko. (However, catching up in plant agriculture is as easy as placing an order from Burpee!)