ps4s - MIT Department of Biology 7.014 Introductory...

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MIT Department of Biology 7.014 Introductory Biology, Spring 2004 Solutions to 7.014 Problem Set 4 Question 1 You have discovered a new virus that contains only RNA as its genetic material. Curious as to how this virus works, you infect cells with this virus and discover that after infection, some DNA that encodes viral proteins is produced At a later time point, lots of viral RNA molecules and various viral proteins are produced. a) Explain what type of virus you have discovered. A Retrovirus. b) Outline the steps of the information flow for this virus by filling in the blanks below. Each arrow represents an activity foe example, DNA polymerse. Circle the arrow that represents a activity that the host cell would not have. RNA protein RNA DNA c) There is a human gene that encodes a protein identical to one of the proteins produced by the virus. When you take the mRNA for this protein and base-pair it with its complementary single-strand human DNA and viral RNA, you're surprised to find that they look different by electron microscopy. Viral RNA + mRNA human DNA + mRNA DNA RNA i) Label which strand is DNA and which is RNA in the human DNA + mRNA picture. ii) Why does the human DNA + mRNA schematic has the shape it does? The DNA contains intron that are spliced out in the final mRNA. 1
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Question 2 Shown below is the genomic structure of the wild-type human β -globin gene. The numbers within the boxes indicate the length (in nucleotides) of each region. The DNA sequences corresponding to the start codon and the stop codon are indicated. = exons = introns Transcription termination Promoter site (also poly A site) ATG TAA 50 90 130 222 850 126 132 TAC ATT Start of transcription 5' 3' 3' 5' a) i) What is the length (in nucleotides) of the wild-type β -globin primary RNA transcript (pre-mRNA)? 1600 ii) How many amino acids are present in the wild-type β -globin protein? 146 b) Give the location of a mutation (m1) in the β -globin gene that would prevent RNA synthesis from the β -globin gene. Promoter c) A base-pair substitution mutation (m2) indicated below, destroys the 3' splice site located in the first intron of the β -globin gene.
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This note was uploaded on 05/02/2009 for the course BIOL 7.014 taught by Professor Walker during the Spring '05 term at MIT.

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ps4s - MIT Department of Biology 7.014 Introductory...

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