Molecular Biology Ch 3
virusoid
Subviral pathogen that causes infectious diseases in higher plants. Circular single-stranded RNA genome. It consists of RNA molecule that does not encode any proteins and requires helper virus for replication and capsid formation
enzyme
a substance that increases the rate or velocity of a chemical reaction without itself being changed in the overall process
RNA bases
bases are modified by adding various atoms or molecules, and tRNA loops each have a separate function. Every tRNA has ACC on the 3' end and coaxial stacking of stems plays an important role in the folding of RNA into a variety of the 3-dimensional shapes
Thomas Cech
his discovery about splicing made him see that the expected R-loops caused by RNA hybriding to the complementary DNA. Revealed that an intervening sequence(IVS) or intron is spliced out in the final 265 rRNA product
RNA world
hypothetical stage in the evolution of life when RNA both carried the genetic information and catalyzed its own replication
mRNA
messenger RNA- a copy of the genomic DNA sequence that encodes a gene product and binds to ribosomes in the cytoplasm
miRNA
microRNA-involved in post-transcriptional gene regulation
proofreading and success of viral diseases
pausing to proofread would slow down rate of replication by RNA polymerase. The success allows viruses to alter proteins rapidly so they can evade recognition by host defense mechanisms
RNP
ribonucleoprotein particle
RNP
ribonucleoprotein particle, an RNA-protein complex
rRNA
ribosomal RNA- essential component of ribosomes
snRNA
small nuclear RNA- plays a role in pre-RNA splicing, a process which prepares the mRNA for translation
snoRNA
small nucleolar RNA-plays a role in rRNA processing
misfolding into a nonfunctional structure
this occurs due to incorrect base pairing
DNA/RNA/Protein world
today, proteins and ribonucleoprotein(RNP) particles catalyze: 1. replication of DNA 2. transcription of DNA into RNA 3. reverse transcription of RNA into DNA
ribozyme
a catalytic RNA molecule (RNA) enzyme catalyzes a number of chemical reactions
Two key points in understanding RNA function
1. RNA can form complementary base pairs with other nucleic acids 2. RNA can interact with proteins
Four ways ribosomes catalyze reactions in same ways proteins do:
1. form substrate binding sites 2. lower the activation energy 3. allow reaction to proceed much faster 4. many are metalloenzymes example: phosphate transfer
catalysis
Necessary for biochemical reactions to proceed at a useful rate. Lowers activation energies
six major types of RNA?
Ribosomal RNA (rRNA), Messenger RNA(mRNA), Transfer RNA(tRNA), Small nuclear RNA(snRNA), Small Nucleolar RNA(snoRNA), MicroRNA (miRNA)
satellite RNA
Subviral pathogen found in plants and animals that replicates only in presence of a helper virus. Single-stranded RNA genome. Larger ones may encode a protein.
Sidney Altman and coworkers
group that showed bacterial RNaseP is an RNA enzyme and that it is the RNA catalyst component
retrovirus
Type of virus that contains RNA as its genetic material and whose replication depends on formation of a DNA provirus by reverse transcription. Originally called RNA tumor virus. Known to cause cancer and aids.
tRNA
Transfer RNA-small RNA that is "charged" with a specific amino acid and delivers to the ribosome the appropriate amino acid via interaction of tRNA anticodon with the mRNA codon. Folds into L-shaped 3-D structure
incorrect base pairing
causes misfolding into a nonfunctional structure
RNP world
during hypothetical transitional period RNA catalyzed the synthesis of proteins and those proteins catalyzed the transition from RNA to DNA
RNaseP
enzyme that cleaves the extra nucleotides for the 5' end of tRNA precursor
Difference between eukaryotic RNA viruses and retroviruses
eukaryotic RNA viruses replicate without any DNA intermediates
small ribozymes
vary in size from 40 to 154 nucleotides. Includes hammerhead motif, hairpin motif, hepatitis delta virus (HDV) RNA. Most are involved in self-replication. Potential tools to combat viral diseases.
large ribozymes
vary in size from few hundred to 3,000 nucleotides. Cleave RNA to generate 3'OH termini. Group I and Group II are self-splicing