The steps of DNA replication and the enzymes involved are largely conserved amongst bacteria, archaea, and
eukaryotes. How can this evolutionary conservation be explained?
What will be an ideal response?
ANSWER: DNA replication is vital to living organisms; it is how they grow, develop, and repair
damaged tissues. Because the process is critical to life, it likely evolved very early and
remained consistent as higher organisms evolved. Changes to the process of DNA replication
are as likely to be detrimental to the process as they are to be beneficial since mutations are
undirected. Thus, if the mechanism of DNA replication is functional and efficient, there
would be no evolutionary pressure to change it.
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Which of the following allows the compilation of time-of-entry maps?
A) the use of many replicates of each experiment B) the use of appropriate controls repeatedly C) the fact that gene entry can proceed in either direction D) the observation that Hfr genes recombine so efficiently E) the recognition of phenotype interaction
After giving birth, female bighorn sheep lick their newborn lambs. This behavior continues off and on for up to 6 hours, after which mothers no longer lick their lambs. What is/are the ultimate cause(s) of this behavior? Check all that apply.
A. Hormones released during labor stimulate motor neurons in female bighorn sheep, causing them to lick and groom their lambs. B. The lamb is stimulated by the licking to begin nursing from its mother and the sooner a lamb begins nursing, the better its chances for survival. C. Licking the lamb removes excess moisture from its coat, preventing hypothermia. D. When licking the lamb, the mother learns its unique scent so she can distinguish it from other lambs and offer it protection from predators or extreme weather. E. Female bighorn sheep remember being licked by their mothers and know they must teach this behavior to their own offspring.
Cancer can be caused by many different factors that all alter genetic information within a set of cells and cause uncontrolled cell division to occur. Which type of gene that causes cancer can be carried in a virus?
A) mutation B) tumor-suppressor gene C) carcinoma D) oncogene
What are the structures labeled E in the accompanying figure?
A. Plasmodesmata B. Basement membranes C. Tight junctions D. Gap junctions E. Adhering junctions