When an open reading frame (orf) is identified, it may not actually correspond to the amino acid sequence of any polypeptide in the cell. why not? (select all that apply.)
a. the dna may not be transcribed into rna.
b. the amino acid sequence may not match any known sequence.
c. the orf could be due to chance.
d. it may contain one or more stop codons in the middle.

Which of the following statements about c4 carbon fixation is not true? a c4 carbon fixation is an adaptation for plants exposed to high light intensityb. c4 carbon fixation occurs in more plants than c3 carbon fixation.c c4 carbon fixation is more common in areas of high temperatures than c3 carbon fixation.d. c4 carbon fixation occurs in the inner cells of a leaf rather than the entire leaf.

Which symbols below represent the ions found in the glass of water ? a. oh- and h+ b. co2 and o2 c. o2 and h2 d. nh3- and h+

Rease is an enzyme used by plants to break down urea (a nitrogen-containing compound) into carbon dioxide and ammonia. urease urea > > > carbon dioxide and ammonia ammonia is broken down by plants into a nitrogen source plants need to grow. thus, plants could not use urea as a nitrogen source unless it was first converted to ammonia. in soybean plants there are two different kinds of urease, one produced in the seeds and the other produced in the leaves of the plant. three types of soybean plants were used in a set of experiments: normal soybeans and two mutant strains, one lacking the urease in the seeds only (strain 1) and one lacking urease in the leaves only (strain 2). experiment 1 separate areas in a field were planted with normal, strain 1, and strain 2 soybeans. all types of soybeans appeared to grow, flower, and produce seeds equally well. there were no externally detectable differences among the strains. experiment 2 small pieces of plant leaves of equal weight were obtained from each type of soybean plant and separately placed on media in culture dishes. tissue growing in this way will become an unorganized clump of cells referred to as callus. to provide a controlled nitrogen source, half the tissue samples of each type were placed on media containing urea, and the other half of the samples were placed on media containing ammonia. after 30 days, the weight gain for each of the callus samples was determined. results are shown in the table below.