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RNA World
Hypothesis that RNA served as the basis of the first form of life -based on: RNAs capacity for storage of genomic information role of RNA in ribosomes enzymatic activity of RNA (ribozymes) TERM 2
Gene Silencing Process
DEFINITION 2 -initiated by dsRNA: a double stranded piece of RNA -have areas of complementation so that one end of the transript will base pari with the other to form a hairpin structure - shares sequence homology with its target mRNA - recognized by the enzyme dicer that cuts it into pieces (21 ncltds) called siRNAs -siRNA then incorporated into protein complex called RISC -surveillence unit that monitors for mRNAs that have homology with the siRNA mRNA is first bound then cleaved prior to translation TERM 3
Gene Silencing
DEFINITION 3 Gene silencing is a general term describing epigenetic processes of gene regulation. - controls the expression of specific genes -mRNA is eliminated prior to translation - underworld of RNA molecules may regulate many aspects of gene expression the control of gene expression through the use of non-coding RNAs TERM 4
Gene Silencing in animals
DEFINITION 4 when homology between the RNA within the RISC complex and the mRNA is not 100%, the mRNA isnt cleaved but physically blocked from translation by binding TERM 5
oncogene
DEFINITION 5 An oncogene is a gene that has the potential to cause cancer. -first identified in viruses -from proto-oncognes by: 1. movements of DNA within the genome (translocation) 2. amplification of proto- oncogenes (increases gene copies) 3.point mutations in the gene - within promoter= increase gene expression - within gene= increase proteins activity
RNAi
RNA interference ; term used to describe homology dependent gene silencing events triggered by double stranded RNA ex: gene silencing TERM 7
siRNA
DEFINITION 7 non coding short RNA (22ncltds) processed from longer dsRNAs during RNA interference : small interfering RNA TERM 8
miRNA
DEFINITION 8 small RNA derived by dicer cleavage of nuclear transcripts - typically contain inverted repeat sequences so that the transcripts develop a 2ndry structure with dsRNA regions : micro RNA TERM 9
Dicer
DEFINITION 9 Dicer is an endoribonuclease in the RNase III family that cleaves double-stranded RNA (dsRNA) and pre-microRNA (miRNA) into short double-stranded RNA fragments called small interfering RNA (siRNA) about 20-25 nucleotides long, usually with a two-base overhang on the 3' end. TERM 10
RISC
DEFINITION 10 RNA-induced silencing complex. -complex of proteins and dsRNA that serves as the site of recognition and destruction of specific ssRNAs
cancer
disease in which cells escape from the control methods that normally regulate cell growth and division -cancer causing agent may be from random spontaneous mutation or environmental influences ( radiation, chemicals, or some viruses) -cancer causing viruses integrate into the cells DNA TERM 17
proto-oncogenes
DEFINITION 17 normal genes that code for proteins that regulate cell division -converted to oncogenes by changes that lead to an increase in the encoded protein or and increase in its activity TERM 18
Tumor-Suppressor Genes
DEFINITION 18 inhibits cell division: -some normally repair damaged DNA, preventing accumulation of mutations -some control adhesion of cells to each other or to the extracellular matrix - some are components of cell-signaling pathways that inhibit the progression of the cell cycle mutations may also contribute to cancer TERM 19
Ras
DEFINITION 19 (product of the ras gene) G protein that relays a growth signal froma growth factor receptor to cascade of protein kinases -at end of pathway is the synthesis of a protein that stimulates the cell cycle ras oncogenes have point mutations that encode a hyperactive version of the ras protein -generates constant signal that results in excessive cell division TERM 20
retroviruses
DEFINITION 20 A retrovirus is an RNA virus that is replicated in a host cell via the enzyme reverse transcriptase to produce DNA from its RNA genome. promotes cancer by integrating their SNA into that of infected cells; by doing to they may: -donate an oncogene -disrupt a tumor-suppressor gene -convert a proto- oncogene to an oncogene -inactivate p
