In different regions of the chromosome, the ratio of histone H1 to histone H2A may vary, but the ratio of H2A to histone H2B is generally the same.
If the amount of H1 increases in a region of chromatin, what will be its effect on compaction of the DNA and transcription in that region?
A. Transcription in that region will increase.
B. Transcription in that region will decrease.
C. The DNA in that region will become less compact.
D. DNA compaction in that region will be unchanged.
E. Transcription of the DNA in that region will remain the same.
How does the RecA protein contribute to the increased expression of SOS genes?
A. RecA protein competes with LexA protein for binding to the operator sequences.
B. RecA protein binds to LexA protein bound to the operator, directly lowering the affinity of LexA protein for DNA.
C. RecA protein binds to free LexA protein, mediating the self-cleavage of the repressor.
D. RecA protein binding to the promoter region recruits RNA polymerase.
The melting point is:
A. the temperature at which double-stranded DNA begins to melt.
B. the temperature at which double-stranded DNA is completely melted.
C. the temperature at which double-stranded DNA is too single-stranded to ever renature back to double strands.
D. the temperature at which double-stranded DNA has become 50 single-stranded.
E. the temperature at which double-stranded nucleic acids degrade into free nucleotides.
The expression of the lac operon in an E. coli cell missing the gene that encodes for the lac repressor:
A. will increase when lactose is present.
B. will decrease when lactose is present.
C. will decrease when glucose is present.
D. will increase when glucose is present.
The LexA protein is:
A. the repressor of the SOS response.
B. the coprotease for the cleavage of RecA protein.
C. a DNA repair enzyme.
D. a regulatory protein for the lac operon.
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