A. ACTB is homologous to ACTC1 but not to MreB.
B. ACTB is orthologous to ACTC1 but not to MreB.
C. ACTB is paralogous to ACTC1 but not to MreB.
D. MreB is orthologous to ACTB but not to ACTC1.
E. ACTB is paralogous to both ACTC1 and MreB.
10.11 Out of nearly 5000 protein-coding gene families, there is a set of nearly 300 conserved gene families that are found in species from all domains of life. When one looks at the general functions assigned to these gene families, it is found that …
A. the majority of them function in cell-to-cell signaling.
B. the majority of them are poorly characterized.
C. more than one-third of them are involved in translation or amino acid transport and metabolism.
D. more than one-half of the shared families are involved in DNA replication and transcription.
E. Nearly all of them are involved in energy production and carbohydrate metabolism.
10.12 Which of the following is true regarding Escherichia coli?
A. Most of our understanding about mitosis comes from studies on this model organism.
B. It is a rod-shaped bacterium that can only grow in the gut of humans and other vertebrates.
C. Two strains of E. coli can differ by up to 0.1% in their genomes.
D. E. coli strain K-12 encodes about 4300 proteins.
E. The E. coli (strain K-12) genome is about 430 million nucleotide pairs long.
10.13 Which of the following is NOT true regarding the tree of life?
A. Most bacteria and archaea have 1000 to 6000 genes in their genomes.
B. Eukaryotes are more similar to archaea than to bacteria with respect to the proteins that act on their DNA.
C. Most bacteria and archaea have genome sizes between one and ten million nucleotide pairs, whereas eukaryotic genomes can be millions of times larger.
D. Archaeal species were thought to belong to the eukaryotic world before sequence analysis placed them in a separate domain of life.
E. Photosynthetic bacteria are thought to be the ancestors of the eukaryotic chloroplasts.
10.14 A mutation in the cdc28 gene in the budding yeast Saccharomyces cerevisiae causes cell-cycle arrest, giving rise to unbudded cells that look like “dumbbells.” Treatment of wild-type cells with nocodazole, a drug that destabilizes some cytoskeletal polymers, leads to a similar phenotype. Based only on these observations, which statement is true regarding cdc28?
A. cdc28 codes for a master regulatory kinase that phosphorylates other proteins.
B. Nocodazole binds to the protein coded by the cdc28 gene.
C. The product of the cdc28 gene is responsible for resistance to nocodazole.
D. The product of the cdc28 gene is involved in cell cycle regulation.
E. The product of cdc28 destabilizes the same cytoskeletal polymers that nocodazole also destabilizes.
10.15 Which of the following structures is exclusively found in eukaryotic cells?
A. Plasma membrane
B. Cell wall
C. Chromosome
D. Ribosome
E. Lysosome
10.16 Mitochondria and chloroplasts are thought to have evolved from free-living aerobic bacteria that were engulfed by an ancestral anaerobic cell and established a mutually beneficial (symbiotic) relationship with it. Which of the following statements is NOT true about these organelles?
A. They are similar in size to small bacteria.
B. They have their own circular genomic DNA.
C. They have their own ribosomes.
D. They have their own transfer RNAs.
E. They are found in all eukaryotes.
10.17 In terms of cellular lifestyle, different kingdoms of life can be likened to hunters, farmers, and scavengers. Which of the following is true in this scheme?
A. The ancestral eukaryotic cell was a farmer, but it turned into a hunter once it acquired mitochondria.
B. Plant cells are considered scavengers, because their cell wall does not allow them to move.
C. Most protozoa are hunters, whereas animal cells are farmers.
D. The ancestral eukaryotic cell was a hunter, but upon acquiring chloroplasts it made the transition into farming.
E. Fungi are scavengers without mitochondria.
10.18 Comparing the genomes of present-day mitochondria or chloroplasts with the genomes of their corresponding bacteria reveals that these organelles do not have many of the genes that are essential for their function. For instance, they lack the many genes that are required for DNA replication. What has happened to these genes?