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Learning about DNA sequence composition by studying DNA renaturation Kinetics

Learning about DNA sequence composition by studying DNA renaturation Kinetics. To denature DNA is to cause the strands to separate Studying how long it takes for complementary pieces to find each other (renature) provides information. Experimentally, this is done using spectroscopy

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Learning about DNA sequence composition by studying DNA renaturation Kinetics

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  1. Learning about DNA sequence composition by studying DNA renaturation Kinetics • To denature DNA is to cause the strands to separate • Studying how long it takes for complementary pieces to find each other (renature) provides information. • Experimentally, this is done using spectroscopy • ss DNA has higher absorbance that ds DNA • What kinds of things have been learned? • Genome size: lots of different genes (larger genome), longer to renature. • Some DNA is present in multiple copies

  2. Graph shows difference in genome size. Different classes of DNA depending on how many copies are present in a cell.

  3. What’s happening in this experiment? ss DNA looking for its complement Complementary pieces base-pairing, become ds, Absorbance decreases. More ss DNA looking for complements, no appreciable change in absorbance. Because [DNA] affects results, data are normalized by [DNA] X Time.

  4. Cot curves and satellite DNA Categories variable among different organisms. Highly repetitive DNA, many complements, find each other quickly. Single copy (unique sequence) much slower. http://www.ndsu.nodak.edu/instruct/mcclean/plsc431/eukarychrom/cot2.gif

  5. Types of DNA • Highly repetitive DNA: 5-45 % of DNA depending on species. In humans: • ALU family: contains Alu I site. 300 bp long, appears 500,000 times, dispersed. 5% of DNA. • SINEs = short interspersed elements • transposable • Alpha satellite DNA: tandem repeats of 170 bp occur 5,000-15,000 times; make up part of centromere. 6% • L1 family (in humans), example of LINEs • Long interspersed elements • transposable

  6. DNA in fewer copies • Moderately (middle) repetitive DNA: • Tandem or interspersed repeats • VNTRs, good for DNA fingerprinting • Variable number tandem repeats • 15 – 100 bp long, between or within genes • Dinucleotide repeats (CA)N, also good for forensic work • in maize and yeasts: transposons in large numbers. • genes for rRNA, ribosomal proteins, histones • Unique, “single copy”: typically 30-75% of DNA in most eukaryotes.

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