The term phenotype refers to:
A.
a computer-enhanced image of the chromosomal makeup of a single organism.
B.
the observable characteristics of an organism as determined by the interaction of genetic and environmental factors.
C.
the complete set of genes that an organism has inherited.
D.
a dominant gene found only on the X chromosome.
The Correct Answer and Explanation is:
The correct answer is:
B. the observable characteristics of an organism as determined by the interaction of genetic and environmental factors.
Explanation:
The term phenotype refers to the observable traits or characteristics of an organism. These traits can include physical features like height, eye color, and flower color, as well as physiological traits such as blood type, behavior, or disease susceptibility.
Phenotype results from the interaction between an organism’s genotype (the genetic makeup or the specific set of genes inherited from its parents) and the environment in which the organism develops. While the genotype provides the blueprint, environmental factors such as nutrition, temperature, stress, and exposure to chemicals can influence how these genes are expressed and manifest as traits.
For example, identical twins share the same genotype but can display differences in phenotype due to variations in their environments. Similarly, a plant species may have the genetic potential to grow tall, but if it lacks sufficient sunlight or nutrients, its actual height (phenotype) may be stunted.
In contrast:
- Option A describes a karyotype, which is a visual representation of an organism’s chromosomes arranged in pairs. This is not the definition of phenotype.
- Option C defines genotype, which is the full set of genes an organism inherits from its parents. The genotype provides the genetic instructions, but does not itself describe the observable characteristics.
- Option D refers to a specific type of gene (a dominant gene on the X chromosome), which is unrelated to the broader concept of phenotype.
Thus, phenotype encompasses the external and measurable expression of genes as shaped by both genetic information and environmental influences. Understanding phenotype is critical in genetics, biology, and medicine because it reflects how genes work in real-world conditions, influencing traits and diseases.
