BIOL125_Ch9 Text Notes

BIOL125_Ch9 Text Notes - BIOL 125 (Microbiology) Text Notes...

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BIOL 125 (Microbiology) Text Notes Chapter 9: Microbial Genetics 1. INTRODUCTION TO GENETICS AND GENES: UNLOCKING THE SECRETS OF HEREDITY a. Genetics – studies the inheritance of biological characteristics by living things. b. The Nature of the Genetic Material i. The Levels of Structure and Function of the Genome 1) Genome – the sum total of genetic material of a cell. a) Most of the genome exists in the form of chromosomes, but genetic material can appear in nonchromosomal sites as well. i) Bacteria and some fungi contain tiny pieces of DNA, called plasmids . ii) Mitochondria and chloroplasts found in eukaryotes have their own genetic material. 2) Genomes are composed exclusively of DNA, except for viruses, which contain either DNA or RNA. 3) The general pattern of nucleic acid structure and function is similar among all organisms. 4) Chromosome – a discrete cellular structure composed of a neatly packaged DNA molecule. a) Eukaryotic chromosomes consist of a DNA molecule tightly wound around histone proteins. i) Eukaryotic chromosomes are located in the nucleus; they vary in number; can occur in pairs (diploid) or singles (haploid); and are linear in format. b) Bacterial chromosomes use histone-like proteins. i) Most bacteria have a single, circular (double-stranded) chromosome. Some do have multiple, circular chromosomes and some are linear. 5) Gene – a certain segment of DNA that contains the necessary code to make a protein or RNA molecule. a) Genes fall into three basic categories: i) Structural Genes – code for protein. ii) Genes that code for RNA. iii) Regulatory Genes – control gene expression. File: d66639ae08ca991c16f14bef7f1349cac3ad1e2b.doc Updated 8/14/09
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Microbiology Text Notes Chapter 9 Page 2 b) Genotype – sum of all three types of genes that constitute an organism’s distinctive genetic makeup. c) Phenotype – the expression of the genotype that creates traits (certain structures or functions). i) The phenotype can change depending on which genes are “turned on” or expressed. ii. The Size and Packaging of Genomes 1) Genomes vary greatly in size. c. The Structure of DNA: A Double Helix with Its Own Language i. DNA – giant molecule, a type of nucleic acid, with two strands forming a double helix. 1) The general DNA structure is universal, however, some viruses contain single-stranded DNA. ii. Nucleotide – basic unit of DNA, composed of phosphate, deoxyribose sugar, and a nitrogen base. iii. Each deoxyribose sugar bonds covalently in a repeating pattern with two phosphates. 1) One of the bonds is to the number 5’ carbon on deoxyribose, and the other is to the 3’ carbon, which specifies the order and direction of each strand. iv.
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BIOL125_Ch9 Text Notes - BIOL 125 (Microbiology) Text Notes...

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