Which of these cell junctions form a barrier to the passage of materials?
-tight junctions
-keratin fibers
-desmosomes (anchoring junctions)
-plasmodesmata
-gap (communicating) junctions
tight junctions
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The integration of phage DNA into the bacterial chromosome occurs because of
A. the phage's ability to synthesize an enzyme that integrates its DNA into the host's chromosome. B. the phage's ability to synthesize enzymes to enter the bacterium. C. similar RNA nucleotides in both. D. the similarity in enzyme metabolism. E. the phage's ability to synthesize enzymes to enter the bacterium AND similar RNA nucleotides in both.
About __________ percent of the 295,000 known
species of flowering plants coevolved with animal pollinators. a. 50 b. 60 c. 70 d. 80 e. 90
Tay-Sachs disease is a human genetic abnormality that results in cells accumulating and becoming clogged with very large, complex, undigested lipids. Which cellular organelle must be involved in this condition?
A) the endoplasmic reticulum B) the Golgi apparatus C) the lysosome D) mitochondrion
Which of the following is evidence supporting the Lyon hypothesis of X inactivation?
A. A highly condensed structure is consistently observed in female cells, but not in normal male cells. B. Female mammals that are heterozygous for X-linked traits are phenotypic mosaics. C. A female cat that is homozygous for coat color cannot have a calico phenotype. D. Calico patterns of coat color are never exactly the same. E. All of the answers are correct.