Biologia della cellule e genoma, test di 11 quesiti a risposta multipla in inglese

CELLS AND GENOMES

Test B1. Which of the following is true regarding Escherichia coli?

1. A. Most of our understanding about mitosis comes from studies on this model organism.
2. B. It is a rod-shaped bacterium that can only grow in the gut of humans and other vertebrates.
3. C. Two strains of E. coli can differ by up to 0.1% in their genomes.
4. D. E. coli strain K-12 encodes about 4300 proteins.
5. E. The E. coli (strain K-12) genome is about 430 million nucleotide pairs long.

2. Which of the following is NOT true regarding the tree of life?

1. A. Most bacteria and archaea have 1000 to 6000 genes in their genomes.
2. B. Eukaryotes are more similar to archaea than to bacteria with respect to the proteins that act on their DNA.
3. C. Most bacteria and archaea have genome sizes between one and ten million nucleotide pairs, whereas eukaryotic genomes can be millions of times larger.
4. D. Archaeal species were thought to belong to the eukaryotic world before sequence analysis placed them in a separate domain of life.
5. E.

Photosynthetic bacteria are thought to be the ancestors of the eukaryotic chloroplasts.3. A mutation in the cdc28 gene in the budding yeast Saccharomyces cerevisiae causes cell-giving rise to unbudded cells that look like “dumbbells.” Treatment of wild-typecycle arrest,cells with nocodazole, a drug that destabilizes some cytoskeletal polymers, leads to a similarphenotype. 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 nocodazolealso destabilizes.

4. Which of the following structures is exclusively found in eukaryotic cells?

A. Plasma membrane

B. Cell wall

C. Chromosome

D. Ribosome

E. Lysosome

5.

1. Fungi are scavengers without mitochondria.
2. 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?
1. They have been lost during evolution, since the organelles no longer rely on DNA replication.
2. The required genes are kept in the nucleus, but many have evolved by gene transfer from the organelle.
3. These genes have undergone mutations and have changed beyond recognition, but are still present in the organelle.
4. The organelles do not replicate their DNA; they import new DNA from the nucleus. The required genes are on plasmids that are separate from the organelle's genome.
3. Based on the variation of genome size and gene number in the organisms presented in the following graph, which organism has the

1. highest number of genes per unit length of their genome? (Note the logarithmic scale.)
   • A. H. sapiens
   • B. M. musculus
   • C. A. thaliana
   • D. C. elegans
   • E. E. coli
2. Which of the following groups of living organisms has the highest variation in haploid genome size?
   • A. Mammals
   • B. Fish
   • C. Fungi
   • D. Protozoa
   • E. Prokaryotes
3. All cells in a multicellular organism have normally developed from a single cell and share the same genome, but can nevertheless be wildly different in their shape and function. What in the eukaryotic genome is responsible for this cell-type diversity?
   • A. The genes that encode transcription regulatory proteins
   • B. The regulatory sequences that control the expression of genes
   • C. The genes that code for molecules involved in receiving cellular signals
   • D. The genes that code for molecules involved in sending cellular signals to other cells
   • E. All of the above
4. Didinium nasutum is a single-celled eukaryote that can hunt and feed on other living cilia, a "mouth opening," an "anal"

and acells. It has an elaborate anatomy with beating aperture,”set of contractile bundles; it can also shoot “darts” to paralyze its prey. What group of living cellsdoes D. nasutum represent?

A. Protozoa

B. Yeasts

C. Algae

D. Animals

E. It can belong to any of the above