Which DNA mutation would likely be the LEAST harmful?
A. A nucleotide substitution in the middle of a gene
B. A base-pair substitution in the start codon
C. A nucleotide substitution in the third position of a codon
D. An insertion or deletion anywhere in the gene
Answer: B. A base-pair substitution in the start codon
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Treponema pallidum is extremely sensitive to temperature changes and low moisture, thus it is transmitted
A) by intimate person-to-person contact. B) by fomites. C) by vectors. D) through common sources such as food and water.
Adding nucleotides onto a growing DNA strand during DNA replication in cells occurs in ____
a. the 5' ® 3' direction for the leading strand and the 3' ® 5' direction on the lagging strand b. either the 5' ® 3' direction or the 3' ® 5' direction on both strands, depending on where replication begins c. the 5' ® 3' direction only d. the 3' ® 5' direction for the leading strand and the 5' ® 3' direction on the lagging strand
e. the 3' ® 5' direction onlyIn green plants, which photosystem absorbs photons to excite electrons in the reaction center?
A. Photosystem I, II and III B. Photosystem II C. Photosystem III D. Photosystem I E. Photosystem I and II
Individuals with an inherited autosomal recessive disorder called primary ciliary dyskinesia (PCD) often have severe respiratory problems due to defective cilia. Males with PCD are often sterile because they produce sperm with defective flagella. Which of the following most likely explains the effect of the recessive allele?
(A) The mitochondria are defective and do not produce sufficient protein to synthesize microtubules in the cilia and flagella. (B) The plasma membrane of the alveoli is not permeable to carbon dioxide during respiration because it is too hydrophobic. (C) The Golgi bodies secrete an enzyme that destroys the proteins in the flagella and cilia. (D) The cells do not produce functional motor proteins in flagella and cilia.