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Lecture

Microbiology and Immunology 2500A/B Lecture Notes - Antibody, Open Reading Frame, Prenylation


Department
Microbiology and Immunology
Course Code
MICROIMM 2500A/B
Professor
C.Y.Kang

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An Intro to Molecular Biology Mar. 8, 2013
Part 1: Genes
What is common between almost everything in the world? All have nucleic acid
Virus: some have their genome in the form of RNA
Animal Cell
o Genome that duplicates the cell are all contained in the nucleus
o Humans have 23 chromosomes
Human Genome Project
23 pairs of chromosomes contain DNA
3.3 billion base pairs
Approximately 35, 000 genes - these are all identifiable genes that can produce proteins
Total length of DNA : 1 x 10^10 Km
Total length can do 33 round trips to the sun or wound up the earth 250, 000 times
Genes
Can produce a protein
Chromosome has DNA & DNA carries the gene
Gene is composed of 4 different bases
G - Guanine
C - Cytosine
A - Adenine
T - Thymine
or in RNA U - Uracil instead of thymine
Most DNA exist as double stranded form
Some viruses exist as single stranded forms
G & A have hydrogen bonds that bind them
C & T have 2 hydrogen bonds that bind them
Groups are bound in chains by sugar phosphate groups
DNA replicates semi-conservatively
Only replicates in one direction, from 3’ to 5’
In order to copy, DNA has to unwind then one strand goes up and another strand
goes down b/c it only copies from 3’ to 5’ direction
Product is 5’ to 3’ (replicate opposite, bind opposite direction)
Pathway of Information Flow in DNA Virus Replication
o DNA can exist as dsDNA or ssDNA
o ssDNA has to go through dsDNA intermediate to make more ssDNA - aka virus
o In cell, dsDNA is transcribed to make mRNA which is translated to make a protein
o Viruses are either ssDNA or dsDNA

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Classification of RNA Virus Genomes
- Single-Stranded RNA Viruses
Positive sense RNA viruses - can be translated to make proteins
Negative sense RNA viruses - complementary to the positive sense
Ambisense RNA viruses - contains both positive & negative sense
- Double-Stranded RNA Viruses
Some small group of viruses contain dsRNA
Pathways of Information Flow of RNA Viruses
In order to make a protein negative ssRNA, you have to make complementary positive
ssRNA which can then be translated from positive ssRNA
Normal cells don’t hold RNA dependent RNA polymerase - unique to RNA viruses, not in
the normal cells (WILL ASK THIS QUESTION)
If is positive ssRNA, it can be translated right away & therefore doesn’t have to carry
RNA polymerase in virus particles b/c as they get into cells they can translate genomic RNA to
become RNA polymerase (few exceptions but this happens in most cases)
ssRNA virus makes mRNA positive which can be translated to make protein
ssRNA positive make dsRNA as intermediate
One unique RNA virus called retrovirus which is positive ssRNA virus but makes DNA
intermediate during replication of this virus
One that goes through DNA intermediate is retrovirus - makes DNA with RNA
they carry
Reverse transcriptase containing virus? aka is positive ssRNA that contains RNA
polymerase
Negative ssRNA viruses must make messenger RNA therefore they have to carry RNA
polymerase
If positive ssRNA. can be translated as they get into the cell & therefore don’t need to
carry enzyme into particles
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