I. RNA As The Genetic Material

    A. Virus:

1. General Characteristics

Infectious particles consisting of nucleic acid enclosed in a protein coat.  They have to rely on the host organism (using hostís enzyme, structured environment) to replicate and  reproduce.
Therefor, viruses areÖ

        Nucleic acid can be          double stranded DNA
                                                single stranded DNA
                                                double stranded RNA
                                                single stranded RNA

2.  Classes of Viruses

        a.  DNA virus  (Bacteriophages, small pox)

        b. RNA virus  (polio virus) and tobacco mosaic virus (TMV).

        c. Retroviruse (HIV, and some form of cancer)

        ssRNA (single stranded RNA ) functions as a template for DNA synthesis, called Retroviruses.

B.  Some viruses contain an RNA core, instead of  DNA --- RNA Viruses and Retroviruses

    RNA is the genetic material of this kind of virus.

C. RNA replication depends on an enzyme, RNA replicase isolated from host E.coli cells.

II. The Structure of RNA

Ribonucleic acid  --- RNA

1. Many single nucleotides are linked to form a polynucleotide chain.
2. The sugar ribose replaces deoxyribose.
3. The nitrogenous base uracil (U) replaces thymine (T)
4. Most RNA is single-stranded with the two following exceptions:

a) RNA molecules some times fold back on themselves to form double-stranded regions of
    complementary base pairs.
b) Some animal viruses that have RNA as their genetic material contain double-stranded helices.

III. Three major classes of cellular RNA molecules function during the expression of genetic
       Ribosomal RNA (rRNA), messehger RNA (mRNA), and transfer RNA (tRNA).

These molecules all originate as complementary copies of one of the two strands of DNA segments during the process of transcription.  Their nucleotide sequence is complementary to the deoxyribonucleotide sequence of DNA, which served as the template for their synthesis.  Uracil replaces thymine in RNA, uracil is complementary to adenine during transcription and during RNA base pairing.

TABLE  10.4  RNA Characterization on your book.

Small nuclear RNA (snRNA):  Participates in processing mRNAs

Telomerase RNA involves in DNA replication at the ends of chromosomes.

Antisense RNA involves in gene regulation.

IV. Acquired Immune Deficiency Syndrome (AIDS)

     AIDS is an immune deficiency disease caused by a virus.

    A. Molecular Biology of HIV

A retrovirus  HIV-1, and HIV-2: the reverse transcribed RNA directing the synthesis of a viral DNA, which is integrated into the host cell genome, the viral genome would direct the production of new virus particles, CD4 molecules on helper T cells function as the major receptor for the HIVvirus instead, not functioning in the normal immune system to help the helper T cells, therefore disable the immune system.

    B. HIV infection:  body fluid containing infected cells, such as semen or blood.

    C. The scope of the HIV epidemic.

        HIV was first identified in 1983,

        HIV entered the U.S. population in the late 1970s.

       513,486 cases of people with AIDS had been
       reported to CDC  in the U.S. as of Dec.31, 1995.

       319,849 had died by the end of 1995, a leading killer
      of people aged 25 to 44 in the U.S.

       Worldwide, an estimated 27.9 million had become
       HIV-infected through mid-1996, and 7.7 million
       had developed AIDS.

        Projection indicated that 40 to 110 million people
        worldwide will be HIV-infected in the 21st century.

 D. AIDS Therapies and Vaccines

 Combination (Cocktail)Therapy, UMís ContributionÖ  Margaret Fischl, M.D., professor of medicine and director of UMís AIDS Clinical Research Unit was an original AZT (most prescribed drugs for AIDS) investigator and lead author of the study report that led to the drugís FDA approval.

In the United States, doctors can prescribe eleven anti-HIV drugs.

These eleven drugs full into three groups:

1.  Nucleoside analog reverse transcriptase inhibitors:  Five drugs.

 2.  Non-nucleoside reverse transcriptase inhibitors: Two drugs.

3.  Protease inhibitors: Four drugs. (AZT)

More information about AIDS, Go TO: http://www.aegis.com/topics/basics/hivandaids.html