Problem S-8: "lac control region configuration".
C-source in growth medium ........................ status of lac control
region
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1. glucose (no lactose) . . . . . . . .. . . repressor bound, thus DNA is looped.
2. glucose and lactose . . . . . . . . .. . no proteins bound; DNA is not looped.
3. lactose (no glucose) . . . . . . . ... . CRP-cAMP bound, DNA is not looped.
4. other (no glucose, no lactose). . . CRP-cAMP & repressor bound, DNA is looped.
Are RNA polymerase molecules able to bind to the promoter and start transcription?
1. No, because the DNA is looped AND there is no CRP-cAMP bound.
2. No (even though the DNA is not looped), because there is no CRP-cAMP bound.
3. Yes, because CRP-cAMP is bound, and the DNA is not looped.
4. No (even though CRP-cAMP is bound), because the DNA is looped.
Problem S-9: "Alternative Splicing".
Gene structure is:
Exon 1 (800 bp) - Intron 1(2000 bp) - Exon 2 (600 bp) - Intron 2 (2000 bp) - Exon 3 (800 bp).
Translated region of mRNA for PA2 is 1800 nucleotides.
Untranslated 5' region of mRNA for PA2 is 200 nucleotides (i.e., the first one-fourth of exon 1).
The mRNA for PA1 (a 400 amino acid protein) has a total length of 1600 nucleotides (first 200 are untranslated 5' region, next 1200 are translated, final 200 are untranslated 3' region.)
Problem S-10: "Synthesis of antibody light chain V5J2C."
Your figure should look like Figure 11.36 in the textbook, except for the following:
The "DNA splice" joins the right side of V5 to the left side of J2, with the deletion of intervening DNA from V6 through J1.
In the B cell DNA, transcription starts just before V5.
The RNA splice joins the right side of J2 to the left side of C, with the region eliminated by RNA processing includes both J3 and J4.
The mRNA (5' V5J2C 3') is translated to produce that IgG light chain polypeptide amino-V5J2C-carboxy.