The transfer of DNA fragments from a dead cell to a live, competent recipient cell that results in a changed recipient cell is
conjugation.
mitosis.
transmission.
transformation.
transduction.
The Correct Answer is D
A. conjugation: Conjugation is the transfer of genetic material between bacterial cells through direct cell-to-cell contact, usually via a pilus. It requires live donor and recipient cells and is not mediated by DNA from a dead cell.
B. mitosis: Mitosis is the process of eukaryotic cell division, resulting in two genetically identical daughter cells. It does not involve horizontal gene transfer or the uptake of DNA from other cells.
C. transmission: Transmission is a general term for the spread of organisms or genetic material but does not specifically describe the process in which a dead cell’s DNA is incorporated into a living recipient cell.
D. transformation: Transformation is the process by which a competent bacterial cell takes up DNA fragments from a dead or lysed cell in its environment. This exogenous DNA can be incorporated into the recipient’s genome, resulting in a genetically altered cell, a mechanism first described in Streptococcus pneumoniae by Griffith.
E. transduction: Transduction is the transfer of bacterial DNA from one cell to another via bacteriophages (viruses that infect bacteria). Unlike transformation, it requires a viral vector rather than direct uptake of free DNA from a dead cell.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
A. Periplasmic flagella: Spirochetes have flagella located within the periplasmic space between the inner and outer membranes. These internal flagella, also called axial filaments, rotate to produce a corkscrew-like motion, allowing the bacterium to move efficiently through viscous environments such as mucus or connective tissue. This unique mechanism is characteristic of genera like Treponema and Borrelia.
B. Pili: Pili are hair-like appendages on the surface of many bacteria used primarily for attachment to surfaces and for conjugation (gene transfer). Pili do not contribute to the corkscrew motility seen in spirochetes.
C. Capsules: Capsules are extracellular polysaccharide layers that protect bacteria from phagocytosis and desiccation. While important for virulence and immune evasion, capsules do not play a role in bacterial motility or the corkscrew movement of spirochetes.
Correct Answer is B
Explanation
A. nucleotide: A nucleotide is the basic structural unit of DNA and RNA, consisting of a sugar, phosphate group, and nitrogenous base. While nucleotides make up the DNA sequence, a group of three bases does not code for a single nucleotide but rather for an amino acid.
B. amino acid: A codon, composed of three consecutive nucleotide bases in DNA or RNA, specifies a single amino acid during protein synthesis. For example, the DNA triplet ATG codes for the amino acid methionine. This triplet code is universal and ensures accurate translation from genetic information to functional proteins.
C. purine: Purines, such as adenine and guanine, are types of nitrogenous bases. They are part of nucleotides, but a triplet of bases does not directly correspond to a single purine; instead, codons dictate amino acids.
D. protein: Proteins are composed of long chains of amino acids. While codons ultimately determine the sequence of amino acids that form a protein, each codon specifies only one amino acid, not an entire protein.
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