Baker_practice_test_3

Baker_practice_test_3 - 1. (10 pts) How are LTRs involved...

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1. (10 pts) How are LTRs involved in transposition of an integrated retrotransposon? Answer: Transcription of a retrotransposon starts within the left hand LTR and stops within the right hand LTR. Then, after conversion of the viral RNA strand into double stranded DNA, the LTR ends of this DNA allow integration, via an LTR-specific transposase (integrase), into a new chromosomal site. 2. (10 pts) (a) What kind of mammalian cells make immunoglobulins? (b) Briefly, how do V and J regions contribute to combinatorial diversity of antibodies in a mammal? (c) Where does transcription start in synthesizing immunoglobulin light chain pre-mRNA? Answer: (a) B lymphocytes. (b) Different lengths and/or positions of a deletion within a V and J chromosomal DNA region results in the attachment of a specific V to a specific J. (c) Transcription, starting at the specific V (PLIV, where P is the transcription promoter sequence), now attached to the specific J, codes for a specific kind of light chain (including the downstream C region). Lab (day and time): _____________________________ TAs: ___________________________ Last Name : _____________________________First Name : ______________________ 2 3. (10 pts) How do aminoacyl synthetase enzymes (“charging” enzymes) contribute to the accurate synthesis of polypeptide chains, each having the correct sequence of amino? Answer: These enzymes attach the correct kind of amino acid to the proper kind of tRNA. 4. (10 pts) (a) If a frameshift mutation occurs at a certain point within a gene, would you expect the transcribed mRNA to be translated in a reading frame that now includes a nonsense codon prior to the position of the original (non-frameshifted) stop codon? (b) If the nonsense codon acts as a translation stop codon, actually stopping translation, would you expect
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Baker_practice_test_3 - 1. (10 pts) How are LTRs involved...

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