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