An organism’s genome stores the instructions that support its cellular activities. This lesson explains how genes, genotype, and phenotype are related, and how environmental conditions can change which genes are expressed.
A gene is a segment of DNA containing instructions for making a protein, an enzyme, or a stable RNA molecule. The order of bases in DNA carries genetic information. Together, all the genes present in an organism’s genome make up its genotype.
All flashcards
What is a gene?
A segment of DNA that contains instructions for a functional product, such as a protein, enzyme, or stable RNA molecule.
What is genotype?
The complete collection of genes present in an organism’s genome. It describes genetic information, not necessarily which traits are currently being expressed.
What is phenotype?
The traits, characteristics, and activities that result from gene expression under particular conditions.
How are constitutive genes different from regulated genes?
Constitutive genes are expressed continually, whereas regulated genes are turned on or off in response to cellular needs or environmental signals.
How does sucrose affect *S. mutans*?
Sucrose can trigger expression of genes for a sticky slime layer, helping *S. mutans* adhere to teeth and form plaque. Its genotype stays the same while its phenotype changes.
Quiz questions
What is a gene?Answer: A segment of DNA containing instructions for producing a protein, enzyme, or stable RNA molecule.
What does the term genotype describe?Answer: The full collection of genes contained in an organism’s genome.
How can phenotype change while genotype remains constant?Answer: Environmental signals can alter which genes are expressed, changing cellular activities and observable traits.
What is a housekeeping gene?Answer: A gene whose product supports basic cellular functions.
A culture of *Serratia marcescens* changes from 28 °C to 37 °C and stops producing red pigment. What is the best explanation?Answer: Temperature changed gene expression, so the phenotype changed without necessarily changing the genotype.
Based on Microbiology by Nina Parker, Mark Schneegurt, Anh-Hue Thi Tu, Philip Lister, Brian M. Forster (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.