A particular flower can be purple, blue, red, or white. A pure-breeding purple plant is crossed with a pure-breeding white plant and the F1 are then crossed to produce an F2 generation. What might a 9:3:4 phenotype ratio in the F2 indicate?
A) reciprocal recessive epistasis
B) codominance
C) dominant epistasis
D) recessive epistasis
E) additivity
D) recessive epistasis
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A researcher discovers a new species of fungi that forms hyphae, but not septa. This fungus also lacks multicellular fruiting bodies, and does not appear to form either endomycorrhizae or ectomycorrhizae with plants. How should this fungus be classified?
A. as a zygomycete B. as a chytrid C. as an ascomycete D. as a glomeromycete E. as a basidiomycete
Which type of base-pair substitution mutation has no effect on the amino acid sequence of a protein?
A) Missense mutation B) Nonsense mutation C) Silent mutation D) Frameshift mutation E) None of these choices
High-energy radiation is often used to treat cancer. The radiation kills the cancerous cells, and the cell cycle checkpoint for DNA repair is overwhelmed. Radiation
a. causes apoptosis at the S and G2 checkpoints. b. inhibits the growth factor at the restriction point. c. blocks DNA replication. d. only causes apoptosis at the tumor site. e. kills all tumor cells without harm to healthy cells.
Which of the following statements about lymphocytes is FALSE?
A) Once they are mature, they migrate to secondary lymphoid organs. B) B and T lymphocytes can be differentiated using a bright-field light microscope. C) Lymphocytes have integral surface proteins by which they can be recognized. D) The glycoproteins on the surface of a lymphocyte are designated with the prefix CD, for "cluster of differentiation." E) Lymphocytes have different types of CD molecules in their cytoplasmic membranes.