Aggcgggtaggcaccctta Tccgcccatccgtgggaat

28. DNA was isolated from a newly discovered worm collected near a deep-sea vent in the Pacific Ocean. This DNA was sheared into pieces, heated to melting, and then cooled slowly. The amount of renaturation was measured with optical absorbance, and the following results were obtained.

What conclusions can you draw about the type of sequences found in this DNA? 29. Which of the following pairs of sequences might be found at the ends of an insertion sequence?

*30. A particular transposable element generates flanking direct repeats that are 4 bp long. Give the sequence that will be found on both sides of the transposable element if this transposable element inserts at the position indicated on each of the following sequences.

(a) Transposable element

5' - ATTCGAACTGACCGATCA - 3'

(b) Transposable element

5' - ATTCGAACTGACCGATCA - 3'

*31. White eyes in Drosophila melanogaster result from an X-linked recessive mutation. Occasionally, white-eyed mutants give rise to offspring that possess white eyes with small red spots. The number, distribution, and size of the red spots are variable. Explain how a transposable element could be responsible for this spotting phenomenon.

*32. An insertion sequence contains a large deletion in its transposase gene. Under what circumstances would this insertion sequence be able to transpose?

*33. What factor do you think determines the length of the flanking direct repeats that are produced in transposition?

34. A transposable element is found to encode a transposase enzyme. On the basis of this information, what conclusions can you make about the likely structure and method of transposition of this element?

35. A transposable element is found to encode a reverse transcriptase enzyme. On the basis of this information, what conclusions can you make about the likely structure and method of transposition of this element?

36. Transposition often produces chromosome rearrangements, such as deletions, inversions, and translocations. Can you suggest a reason why transposition leads to these chromosome mutations?

37. A geneticist studying the DNA of the Japanese bottle fly finds many copies of a particular sequence that appears similar to the copia transposable element in Drosophila. Using recombinant DNA techniques, the geneticist places an intron into a copy of this DNA sequence and inserts it into the genome of a Japanese bottle fly. If the sequence is a transposable element similar to copia, what prediction would you make concerning the fate of the introduced sequence in the genomes of offspring of the fly receiving it?

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