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Chapters 1-2. Mendelian Genetics and Nucleic Acid Structure. 23 August, 2006. Overview. Mendel refuted the blending hypothesis, proposing particulate units of inheritance - genes. The idea of genetic inheritance gained support from the behavior of chromosomes in meiosis and fertilization.
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Chapters 1-2 Mendelian Genetics and Nucleic Acid Structure 23 August, 2006
Overview • Mendel refuted the blending hypothesis, proposing particulate units of inheritance - genes. • The idea of genetic inheritance gained support from the behavior of chromosomes in meiosis and fertilization. • Linkage analysis can give information about the relative location of genes on chromosomes. • The success of Mendelian genetics increased the importance of characterizing the genetic material. • Chromosomes are composed of DNA and protein - the DNA is the genetic material. • Nucleic acid structure gives important insight into genetic function.
Review of Mendelian Inheritance • Genes influence characters, and may occur in a number of different allelic forms. • Each organism / cell has two copies of each gene, and may be homozygous or heterozygous. • Gametes carry a single allele of each gene. Alleles are distributed randomly to gametes. • Fertilization combines the alleles present in the two participating gametes.
Incomplete Dominance Independent Assortment
Linkage and Recombination • Linked genes are carried on the same chromosome. • Homologous chromosomes exchange genetic material during synapsis. This changes the combinations of alleles that are possible • Recombination frequency is proportional to physical distance.
Genetic maps use crossover frequency to order groups of linked genes.
Genes are carried on chromosomes, and are inherited unchanged and undiluted. • Mutations are rare events that change one allele to another. • A genetic material that was inherited unchanged and undiluted, but subject to rare mutation answered a major flaw in evolutionary theory. • The success of genetics intensified interest in the nature of the genetic material. • Chromosomes are composed of DNA and Protein. Most biologists thought that Protein was the genetic material, while DNA was structural.
DNA is the Genetic Material • DNA but not protein can transform bacteria.