Genomic Repetitive Elements (Human Focus)
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Genomic Repetitive Elements(Human Focus)
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TYPES OF ELEMENTS
Tandem repeats:a) satellite DNA
1) centromeric and heterochromatic2) minisatellite3) microsatellite
b) telomers
Interspersed repetitive elements:a) transposons
1) Class I – copy and paste (RNA intermediate)a) retrotransposons (no envelope protein)b) Long Interspersed Nuclear Elements (LINES)c) Short Interspersed Nuclear Elements
(SINES; example: Alu)2) Class II – cut and paste (DNA element)
b) Endogenous Retroviruses (ERVs) (contain Envelope Proteins)
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Relationship of retroelements
Retroelements
Retroviruses
Class I retrotransposonsTHE1, copia, Ty
Class II retro-transposons
loss of LTR
loss of env
loss of pol (RT)
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Viral Envelope Protein
Matrix
Integrase Protein
Reverse Transcriptase
NucleocapsidViral RNA genome
Capsid
polgag envLTR LTR
Retrovirus
10 KB in size
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Nuclear Translocation
Retrovirus Replication Cycle
Virus Entry
Uncoating & Reverse Transcription
Integration intohost genome
Transcription
Translation
Release &Maturation
Assembly
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FOR RETROVIRUSES REVERSE TRANSCRIPTION . . .
A) OCCURS IN THE CYTOSOL
B) USES A t-RNA PRIMER TO INITIATE REVERSE TRANSCRIPTION
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Retroviruses
Somatic CellsGermline Cells
e.g., liver cells
virus NOT passed on to progeny
Ovum Sperm
virus passed on to progeny
Endogenous Retrovirus (ERV) Exogenous Retrovirus
Infection leads to
integration of retrovirus
genome into the host genome
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Germline Cells
Repeated infections in the germline are referred to as “expansions”
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LINES AND SINES
LINE Proteins:Orf 1 – RNA binding protein
Orf2 – Reverse transcriptaseEndonuclease activity
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FOR LINES AND SINES REVERSE TRANSCRIPTION . . .
A) OCCURS IN THE NUCLEUS
B) USES THE NICKED DNA TO INITIATE REVERSE TRANSCRIPTION
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WHAT ARE THE GENOMIC AND EVOLUTIONARYCONSEQUENCES OF THESE MOBILE ELEMENTS?