Which of the following substances helps make cells of xylem rigid to avoid collapse?
A. cellulose
B. lignin
C. chitin
D. spongin
E. parenchyma
B
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Which of the following statements about the evolution of animal cell adhesion molecules is true?
A. Animal cell adhesion molecules evolved from protein families that originally performed other functions. B. The genes for integrins are found in all opisthokonts including animals, plants, and fungi. C. The genes for cadherins are only found in animals. D. The genes for integrins are found only in multicellular organisms. E. All of these statements about the evolution of animal cell adhesion molecules are true.
In some genetically engineered corn plants, a Bt gene was added to a chromosome. The Bt gene specifies a protein called Bt that is lethal to certain flying insect pests that eat the corn plants. If the corn plant is is heterozygous for the Bt gene (one homolog has the introduced Bt gene and the other does not), what proportion of the sperm would carry the Bt gene? Is the presence of the Bt gene (a mutation) dominant or recessive to its absence (the wild type)?
A) all pollen; dominant B) 1/2; dominant C) 1/3; recessive D) 1/4; dominant E) 1/8; recessive
The majority of DNA in a cell that has undergone differentiation is _____
a. transcribed b. translated c. turned off d. mutated e. hydrolyzed
Legumes, such as beans or peas
A) form mutualistic associations with nitrogen-fixing bacteria. B) form mycorrhizal associations to increase nitrogen fixation in the soil. C) form parasitic relationships with other photosynthetic plants. D) fix N2 from the atmosphere in their leaves.