Cellule e genoma, test a risposta multipla in inglese con risposte

Formattazione del testo

A. Swimming using flagella
B. Having a cell wall around the plasma membrane
C. ATP production in mitochondria
D. Protein production on the ribosome
E. Sexual exchange of DNA with other bacteria
6. To trace family relationships between distantly related organisms such as humans, algae, genomes in regions bacteria, and archaea, one should compare their
A. that evolve rapidly.
B. that have a higher mutation rate.
C. that code for proteins.
D. where mutations are hardly tolerated.
E. where most mutations are selectively neutral.
7. Laboratory strains of the model organism Escherichia coli that are resistant to antibiotics are very often used in research laboratories as well as in the biotechnology industry. If cultures of such bacteria were allowed to contaminate the environment uncontrollably, it is possible that at some point, pathogenic bacteria such as Neisseria meningitidis (which causes meningitis and can cause death, especially in children) could acquire the same antibiotic-resistance gene.

causing ameningitis outbreak that is difficult to treat. In this scenario, which of the following mechanismsis a more likely source of the antibiotic-resistance gene in N. meningitidis?

A. Random new gene generation

B. Intragenic mutation

C. Gene duplication

D. DNA segment shuffling

E. Horizontal gene transfer

A virus …8. A. is a type of cell.

B. has genetic material made of proteins.

C. can only infect a single host species.

D. can act as a vector for gene transfer.

E. cannot persist in its host for more than one cell generation.

9. Which of the following does NOT typically involve horizontal gene transfer?

A. Sexual reproduction in humans

B. Bacteriophage infection of bacteria

C. The evolutionary history of the eukaryotic cell

D. The accidental duplication of a small region of a bacterial chromosome followed bycell division

E. Introduction of plasmids into bacteria in a laboratory

10. Gene duplication can give rise to homologous genes that are part of gene families. Forexample, there are six

actin genes in the genome of most mammalian species. In humans, the ACTB gene, which encodes a cytoskeletal actin, is expressed ubiquitously, while ACTC1 is expressed mainly in cardiac cells. Although bacteria lack the eukaryotic cytoskeletal organization, the bacterial MreB gene bears recognizable sequence similarity to mammalian actin genes and codes for a protein that is similar to actin in structure and function. Which of the following statements is true about these genes? 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. 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 A. the majority of them function in

A. 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.

Answers

1. Answer: C

Feedback: All living organisms are made of cells. However, only a minority of them are eukaryotes with defined cell nuclei. Not all cells obtain their energy directly from sunlight. However, regardless of the energy source, the main energy currency used by all known living cells is ATP. Some prokaryotic genomes contain only a few hundred genes.

2. Answer: E

Feedback: All living cells replicate their DNA by the same overall mechanism of templated polymerization. They also transcribe the genetic information into RNA form using the same mechanism. Translation of this information into protein form is mediated by the ribosome in all cells.

Additionally, all cellular membranes have membrane transport proteins that control the flow of material through the membranes. 3. Answer: B 3 Feedback: There are 64 (that is, 4³) nucleotide triplets or codons using four types of nucleotide monomers, whereas each codon encodes one out of only 20 amino acids. Therefore, some sequence information is lost when translating from mRNA to protein sequences, such that it is not usually possible to deduce the original mRNA sequence given a translated polypeptide sequence. 4. Answer: C Feedback: Diffusion is a spontaneous process driven by the thermal energy of randomly moving molecules, and normally does not require energy expenditure by the cell. For the other mentioned processes, free energy is required. If a cell "dies," these processes would stop or get out of control, but small molecules would still diffuse. 5. Answer: C Feedback: Bacterial cells do not have membrane-enclosed organelles such as mitochondria. 6. Answer: D Feedback: Highly

Conserved genes that code for optimized, essential, protein or RNA molecules should be studied to trace family relationships across distant taxa. Mutations in these regions (such as the genes that code for ribosomal RNAs) are usually eliminated, making the sequence recognizable even after billions of years of evolutionary history.