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Microbial Genetics - Microbial Genetics Genetics is defined...

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Microbial Genetics Genetics is defined as the mechanism by which traits are passed on from one organism to another and how they are expressed. How does information flow? Central dogma of molecular biology: Replication - to ensure that following generations acquire genetic material Transcription - intermediate process between DNA and protein synthesis. Generates mRNA, rRNA and tRNA. Translation - messenger RNA is translated by ribosomes into a polypeptide based on genetic code of the nucleic acids. Genetic code is made up of "words" that are 3 bases long called a codon. So central dogma of molecular biology is that genetic information flows from DNA through RNA to protein. Genetic information - genetic information is stored primarily in DNA . What is DNA ? DNA is composed of four nucleotides adenine , guanine , cytosine and thymine . Each nucleotide is composed of a nitrogenous base, deoxyribose, and phosphate groups. DNA is a polynucleotide molecule where the backbone is a sugar phosphate backbone and the nitrogenous bases stick out like rungs on a ladder. The phosphate linkage is called a phosphodiester linkage between the 5 prime phosphate group of one sugar and the 3 prime hydroxyl group on the second sugar. DNA is a double helix where two polynucleotide strands that are complementary are held together by hydrogen bonds . Specifically adenine and thymine complement each other and guanine and cytosine complement each other. The two strands are oriented in an antiparallel fashion meaning that one strand runs 5 prime to 3 prime and the complement is 3 prime to 5 prime. The DNA is not a ladder but rather has a twisted about it which gives it it's helical nature. Chromosome - single circular double stranded helix that codes for indispensable functions - so called house keeping genes. The cell's genotype (potential) is its genetic makeup and represents its potential properties. The cell's phenotype (actual) is the actual expressed properties of a cell. A cell's phenotype is a manifestation of its genotype. The amount of DNA in a microorganism may be in the thousands of kilo base (Kb) pairs. E. coli has about 4700 Kb pairs which is about 1.5 millimeter in length if it were linear but bacterial chromosomes are circular. Problem still is getting the entire DNA in a cell. How do they pack the DNA in a cell? The answer is as a super coiled molecule . Super coiled DNA is double stranded DNA further twisted in what is either negatively or positively super coiled. Most DNA in nature is negatively super coiled. Super coiled DNA is only stable if the two strands are intact. If one strand is nicked, the super coil tension is relaxed and the DNA is in a relaxed state. DNA Replication Making a second copy of the chromosome before the cell divides.
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