Repressible genes are usually actively transcribed when:a
repressor molecules bind to the promoter.
b. the supply of the end product formed by the enzymes encoded by these genes is low.
c. tryptophan accumulates in the cell.
d. quantities of precursor materials are high.
e. there is no other substrate that can be used by the cell.
B
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Why have growth rates increased the most in developing countries in the past 50 years?
A. Individuals in the population are living longer lives. B. Death rates have decreased as compared to birthrates. C. Death rates have increased as compared to birthrates. D. Individuals in the population are living shorter lives. E. Death rates are equal to birthrates.
In plants, primary and secondary cell walls, though distinctly different, share all of the following molecules except
a. cellulose. b. hemicelluloses. c. pectin. d. peptidoglycans.
All of these statements about Chlamydomonas are true EXCEPT ________.
A. Chlamydomonas only reproduces asexually B. each motile Chlamydomonas cell has a single haploid nucleus C. Chlamydomonas has two flagella D. Chlamydomonas is photoautotrophic
What was the first disease shown to be bacterial in origin?
A) yellow fever B) cholera C) anthrax D) malaria E) tuberculosis