In the pressure-flow mechanism, loading of sucrose from companion cells to sieve-tube elements takes place through _____
A) plasmodesmata
B) facilitated diffusion
C) sucrose-H+ symporters
D) sucrose-H+ antiporters
A
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An allele is:
A. one of several forms of a gene. B. the particular combination of genes for a given trait in a given organism. C. the expression of a trait in an individual. D. the location of a gene on a chromosome. E. none of these.
Which of the following countries is most likely to have a pyramid-shaped age structure?
a. Niger b. The United States c. Sweden d. Italy
What happened in an experiment where normal cultured human cells were infected with a virus that carried DNA
encoding for the telomerase catalytic subunit? a. The cells underwent more cell divisions than normal. b. The cells underwent fewer cell divisions than normal. c. The cells died almost immediately. d. The cells did not express the foreign telomerase gene. e. The cell cycle shortened.
Master genes that affect development tend to be highly ____; therefore, similarities in patterns of embryonic development reflect shared ancestry that can be evolutionarily ancient.
a. homologous
b. degraded
c. conserved
d. mutated
e. related