Some combinations of recessive alleles cause problems so severe that a fetus may cease to develop. Such lethal allele combinations appear to alter Mendelian ratios because
A) carriers do not constitute a progeny class.
B) they do not show a 1:2:1 genotypic ratio.
C) homozygotes for the lethal allele do not appear as a progeny class.
D) homozygotes for the lethal allele pass it on to half their offspring.
C) homozygotes for the lethal allele do not appear as a progeny class.
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Which of the following is/are used to identify methicillin-resistant Staphylococcus aureus?
A) selective media B) differential media C) PCR D) selective media, differential media, and PCR
Each type of cone cell is stimulated by a different color of light. In humans, a colorful scene is perceived as a combination of signals from three cone types. Which colors correspond to these three cones?
I-Red II-Yellow III-Orange IV-Blue V-Green VI-Purple A. I, II, and III B. I, III, and IV C. I, IV, and V D. I, V, and VI E. II, IV, and VI
Which of the following is NOT a characteristic of a virus?
A. Containing nucleic acid B. Surrounded by capsid proteins C. Containing ribosomes for translation D. Nonliving
All of the following organisms produce exotoxins EXCEPT
A) Salmonella typhi. B) Clostridium botulinum. C) Corynebacterium diphtheriae. D) Clostridium tetani. E) Staphylococcus aureus.