09_Genes_and_Mutation

09_Genes_and_Mutation - The Nature of the Gene, Alleles,...

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Unformatted text preview: The Nature of the Gene, Alleles, and Mutation Today’s questions: At the molecular level, what is a gene? An allele? A mutation? I. The molecular nature of the gene II. The central dogma of molecular biology III. The molecular nature of mutation (cell phones off, please) I. The molecular nature of the gene The current definition of the gene: What What do we know about genes? 1. Genes are made of DNA A T G T G T G T G G C C G T A T G C T G G T A T G C T C T A C A C A C A C C G G C T A A C G A C C A T A C G A G (a chromosome is one long DNA molecule 2. Sets of 3 bases in DNA can specify an amino acid—a building block of a protein A T G T G T G T G G C C G T A T G C T G G T A T G C T C T A C A C A C A C C G G C T A A C G A C C A T A C G A G What What do we know about genes? 3. Genes include regions that code for RNA or protein products that 4. … as well as regulatory regions II II. The central dogma of molecular biology DNA siRNA,tRNA, rRNA, snRNA, et al. (enzymes, fibers, receptors, motors, pumps, channels etc.) Genes (DNA) represent the genotype Proteins and RNAs (gene products) represent the phenotype 1. At the molecular level, what is the “gene for flower color”? 2. What happens to the genotype and phenotype if there is a change in the sequence of bases in the coding region of a gene? 3. What happens to the genotype and phenotype if there is a change in the sequence of bases in the regulatory regions of a gene? III III. The molecular basis of mutation When chromosomes replicate, DNA is copied by enzymes. The enzymes make mistakes, at random. 1. What are the consequences of these mistakes, for the genotype? 2. Many copying errors change the DNA base sequence, and also change the RNA or protein product. • How do these errors affect the phenotype? • Do these errors create alleles? 3. Some copying errors change the DNA base sequence, but do not change the protein product. • How do these errors affect the phenotype? • Do these errors create alleles? 4. Mistakes in meiosis can lead to a doubling of the number of chromosomes or other changes in chromosome number (e.g. if homologs fail to pull apart). • Do these errors affect the genotype? • Do these errors affect the phenotype? 5. Damage from ultraviolet radiation or toxic chemicals can break chromosomes. • Do these changes affect the genotype? • Do these changes affect the phenotype? ...
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