The red blood cells of people with sickle cell anemia have abnormal shapes due to ____
a. hemoglobin molecules with mutant beta globin subunits sticking together and forming long fibers in the
cytoplasm
b. destruction of the hemoglobin molecules
c. loss of hemoglobin through leaky cell membranes
d. the attachment of phosphate groups to the hemoglobin molecules
e. the binding of methyl groups to the heme group of the hemoglobin molecule causing desiccation of the cells
a
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Terrestrial vertebrates and some fish evolved a form of fertilization in which the male gametes are introduced into the female reproductive tract. What is this called?
A. synchronous fertilization B. external fertilization C. internal fertilization D. asexual fertilization
Typically, multiple interacting genes and the environment contribute to a complex quantitative trait, resulting in
A) discontinuous distribution of discrete phenotypes. B) continuous variation of the trait in a population. C) strict dominance of a single allele so that one phenotype is most common. D) continuous variation of the trait in a single individual.
Attachment of herpesviruses results in ________, a process in which the host cell facilitates viral entry
A) direct penetration B) membrane fusion C) endocytosis D) exocytosis E) lysogeny
What do you think would result if nitrogen-fixing cyanobacteria populations suddenly declined?
A. Aquatic primary production would decline, particularly in regions not subject to fertilizer runoff. B. Legumes would cease to grow, but other types of plants would be unaffected. C. Both the aquatic and terrestrial populations of autotrophs would collapse. D. Populations of denitrifying bacteria would expand to take over their role, creating only a temporary disruption. E. More nitrogen would become available for other aquatic autotrophs.