Ch_11_TEs - Interested in research? Apply to UBRP for the...

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Unformatted text preview: Interested in research? Apply to UBRP for the Summer of 2009! Applications available on line at: https://ubrp.arizona.edu Deadline: February 1, 2009 Chapter 11: Transposable Elements Types of DNA Sequences ¡ Unique-sequence DNA ¡ Gene families ¡ Moderately repetitive DNA ¡ Highly repetitive DNA Small Copy Number ¡ Unique-sequence DNA – present once (or a very few times) in the genome ¢ Comprise 25-50% of protein-encoding regions in multicellular eukaryotes ¡ Gene families – similar (but not identical) copies that arose through duplication of an existing gene ¢ e.g. β-globin (7 copies), immunoglobulin (100s of copies) Moderate Copy Number ¡ Moderately repetitive DNA ¢ Sequences 150-300 bp long repeated thousands of times ¢ e.g. genes for rRNAs and tRNAs, many with unknown function ¡ Tandem repeat sequence – clustered together ¡ Interspersed repeat sequences – scattered throughout genome ¢ SINEs (short interspersed elements) ¢ e.g. Alu sequence ~200 bp, > million copies, no known function ¢ LINEs (long interspersed elements) Large Copy Number ¡ Highly repetitive DNA ¢ Short sequences <10bp present in 100,000-1million copies ¢ Repeated in tandem ¢ Clustered, especially near the centromeres and telomeres ¢ Sometimes called satellite DNA ¢ Most have no known function ¢ Found in heterochromatin Transposable Elements ¡ Mobile DNA sequence found in the genomes of all organisms ¡ Abundant, ~45% of human DNA ¡ Can insert in many locations ¡ Do not require homologous recombination to insert ¡ Create DNA rearrangements (duplications, deletions, inversions) ¡ Barbara McClintock won the 1983 Nobel Prize for their discovery ¡ Transposition is the movement of a transposable element from one location to another ¡ Common features ¢ staggered breaks are made in the target DNA ¢ the TE is joined to single-stranded ends of the target DNA ¢ DNA is replicated at the single-stranded gaps Transposition Structure of Transposable Elements ¡ Transposable elements are DNA sequence lengths (usually thousands of bp) that ¢ are capable of moving from one site to another (without recombination) ¢ do include a terminal inverted repeat ¢ do NOT include a flanking direct repeat ¡ Vary in size and structure but have some common features ¢ Not part of the TE and do not move with it ¢ 3-12 bp ¡ How are they created? ¢ Staggered cuts are made at the site of insertion ¢ Replication of the ssDNA at the staggered cuts creates flanking direct repeats 5’ – TGCAA… …TGCAA- 3’ 3’ – ACGTT… …ACGTT- 5’ Flanking Direct Repeats Terminal Inverted Repeats ¡ Sequences 9-40 bp that are inverted and complementary of one another...
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This note was uploaded on 01/30/2010 for the course ECOL 320 taught by Professor Weinert during the Fall '07 term at Arizona.

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Ch_11_TEs - Interested in research? Apply to UBRP for the...

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