Before gastrulation, the future destiny of cell lineages is largely established by ____
a. the genotype
b. the portion of egg cytoplasm
c. surface recognition factors on the plasma membrane
d. the number and type of organelles
e. the sperm cytoplasm
b
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Several of the different globin genes are expressed in humans, but at different times in development. What mechanism could allow for this?
A) exon shuffling B) intron activation C) pseudogene activation D) differential translation of mRNAs E) differential gene regulation over time
Which of the following is true of the mechanism of transcription attenuation of the trp operon?
A. The leader peptide mechanism is analogous to a repressor protein. B. The ribosome stalls at the adjacent Trp codons when the levels of tryptophan in the cell are high. C. The stalling of the ribosome at region 1 of the leader sequence inhibits the formation of the terminator structure. D. When sequences 2 and 3 of the leader sequence associate, transcription is terminated prematurely.
Refer to the figure. After the system reaches equilibrium, what changes are observed?
A) The molarity of sucrose is higher than that of glucose on side A. B) The water level is higher in side A than in side B. C) The water level is unchanged. D) The water level is higher in side B than in side A.
Which of the following statements regarding toxoids is FALSE?
A. They produce immunity to the toxin of the microorganism rather than the microorganism itself. B. They provide lifelong immunity. C. They stimulate antibody immune responses. D. They have few antigenic determinants. E. They are chemically or thermally modified.