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MICROBIAL MOLECULAR BIOLOGY & GENETICS

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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 prokaryotes. DNA synthesis in
higher organisms is less well understood,…

MICROBIAL MOLECULAR BIOLOGY & GENETICS

Image
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, but may also contain
nonchromosomal DNA in the form of plasmids. The genetic inform…

MICROBIAL MOLECULAR BIOLOGY & GENETICS

Image
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 nucleotide sequence of DNA (and
sometimes RN…