MICROBIOLOGY

A)  Genes: Structure, Replication & Mutation STEPS IN PROKARYOTIC DNA SYNTHESIS   When the two strands of the DNA double helix are separated, each can serve as a template for the replication of a new complementary strand. This produces two daughter molecules, each of which contains two DNA strands with an anti parallel orientation . This process is called semi conservative replication because, although the parental duplex is separated into two halves (and, therefore, is not “conserved” as an entity), each of the individual parental strands remains intact in one of the two new duplexes . The enzymes involved in the DNA replication process are template-directed polymerases that can synthesize the complementary sequence of each strand with extraordinary fidelity. The reactions described in this section were first known from studies of the bacterium Escherichia coli (E. coli ), and the description given below refers to the process in pro...

A) Genes: Structure, Replication & Mutation    Nucleic Acid Structure:   The structure and synthesis of purine and pyrimidine nucleotides as you all know.  These nucleotides can be combined to form two types of nucleic acids; Deoxyribonucleic acid(DNA) & Ribonucleic acid( RNA). Ribonucleic acid    is composed of the ribonucleosides of adenine, guanine,   cytosine, and uracil (instead of thymine).  In both DNA and RNA, nucleosides are joined by phosphate groups to form long polynucleotides. Nucleic acids are required for the storage and expression of genetic information. There are two chemically distinct types of nucleic acids: deoxyribonucleic acid (DNA) and ribonucleic acid . DNA, the repository of genetic information, is present not only in chromosomes in the nucleus of eukaryotic organisms, but also in mitochondria and the chloroplasts of plants. Prokaryotic cells, which lack nuclei, have a single chromosome, ...

  A) Genes: Structure, Replication & Mutation Concepts 1. The two kinds of nucleic acid, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), differ from one another in chemical composition and structure. In procaryotic and eucaryotic cells, DNA serves as the repository for genetic information. 2. DNA is associated with basic proteins in the cell. In eucaryotes these are special histone proteins, whereas in procaryotes nonhistone proteins are complexed with DNA. 3. The flow of genetic information usually proceeds from DNA through RNA to protein. A protein’s amino acid sequence reflects the nucleotide sequence of its mRNA. This messenger is a complementary copy of a portion of the DNA genome. 4. DNA replication is a very complex process involving a variety of proteins and a number of steps. It is designed to operate rapidly while minimizing errors and correcting those that arise when the DNA sequence is copied. 5. Genetic information is contained in the nuc...