Genes that are not required for survival, but are likely to be beneficial to the organism, are called ________.

Question

BlackTom AI · Accepted Answer

Nonessential genes are genes that an organism can live without under standard conditions but that often confer a selective advantage in particular environments or situations.

Relevant knowledge points: An essential gene is required for basic survival—loss of function is lethal. Nonessential (also called dispensable or accessory) genes are not required for viability but can improve fitness, survival, or reproduction in specific contexts. Lethal, semilethal, and conditional lethal refer to allele effects on viability: lethal alleles cause death when present (usually in homozygotes), semilethal alleles cause death in some but not all individuals, and conditional lethal alleles cause death only under particular environmental conditions.

Step-by-step reasoning:
1. The stem specifies genes “not required for survival” — that rules out any term implying required-for-life (i.e., essential).
2. It further states they are “likely to be beneficial” — implying they improve fitness but are not strictly necessary.
3. The term that precisely matches “not required for survival but likely beneficial” is nonessential genes (also described as dispensable or accessory genes in genomic literature).
4. Compare alternatives:
   - essential genes: by definition required for survival; incorrect.
   - lethal alleles: describe specific alleles that cause death, not genes that are merely beneficial; incorrect.
   - semilethal alleles: reduce survival in a fraction of carriers, not simply beneficial but nonessential; incorrect.
   - conditional lethal alleles: cause death only under certain conditions; these are allele effects tied to environment, not the general idea of beneficial-but-not-required genes; incorrect.

Why the correct answer is correct: Nonessential genes do not compromise viability when lost, yet they often provide advantages (e.g., antibiotic resistance genes, metabolic pathways for alternative substrates, virulence factors). They fit both parts of the description—“not required for survival” and “likely to be beneficial.”

Conclusion: The correct choice is nonessential genes, which matches the provided answer.

Genes that are not required for survival, but are likely to be beneficial to the organism, are called ________.单项选择题

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