Introduction to Genetics PDF

Introduction to Genetics Asst. Prof. Beste Tacal ASLAN  Genetics is the scientific study of genes and heredity—of how certain qualities or traits are passed from parents to offspring as a result of changes in DNA sequence. The transmission of traits from one generation to the next...

Introduction to Genetics Asst. Prof. Beste Tacal ASLAN  Genetics is the scientific study of genes and heredity—of how certain qualities or traits are passed from parents to offspring as a result of changes in DNA sequence. The transmission of traits from one generation to the next is called inheritance, or heredity. However, sons and daughters are not identical copies of either parent or of their siblings. Along with inherited similarity, there is also variation. The true starting point of our understanding of genetics began in a monastery garden in central Europe in the 1860s, where Gregor Mendel, an Augustinian monk, conducted a decade-long series of experiments using pea plants. His work forms the foundation for genetics. Basis of the chromosome theory of inheritance, which states that inherited traits are controlled by genes residing on chromosomes faithfully transmitted through gametes, maintaining genetic continuity from generation to generation. Alleles are defined as alternative forms of a gene. The variant eye color gene discovered in Drosophila is an allele of a gene controlling eye color. Mutations are defined as any heritable change and are the source of all genetic variation. Different alleles may produce differences in the observable features, or phenotype, of an organism. The set of alleles for a given trait carried by an organism is called the genotype. If the larvae develop early in the year, when days are shorter and colder, the butterflies (Junonia coenia) reach maturity in summer with tan wings. But if larvae develop later in the year, when days are longer and warmer, the butterflies mature in fall with reddish wings. Researchers in the last decades of the nineteenth century also described the behavior of chromosomes during two forms of cell division, mitosis and meiosis. In mitosis, chromosomes are copied and distributed so that each daughter cell receives a diploid set of chromosomes. Meiosis is associated with gamete formation. THE HUMAN LIFE CYCLE  How did scientists determine that DNA is the hereditary material? Investigators turned their attention to identifying which chemical component of chromosomes carried genetic information. By the 1920s, scientists were aware that proteins and DNA were the major chemical components of chromosomes. Of the two, proteins are the most abundant in cells. There are a large number of different proteins, and because of their universal distribution in the nucleus and cytoplasm, many researchers thought proteins would be shown to be the carriers of genetic information. Viruses that attack bacteria are called bacteriophages, or phages for short, and like all viruses, consist of a protein coat surrounding a DNA core. Experiments showed that during infection the protein coat of the virus remains outside the bacterial cell, while the viral DNA enters the cell and directs the synthesis and assembly of more phage.  The science of today is the technology of tomorrow