I. RNA As The Genetic Material
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
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
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
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