Question

If one is attempting to determine the influence of genes or the environment on phenotypic variation, inbred strains with individuals of a relatively homogeneous or constant genetic background are often used. Variation observed between different inbred strains reared in a constant or homogeneous environment would likely be caused by genetic factors. What would be the source of variation observed among members of the same inbred strain reared under varying environmental conditions?

Short answer

Answer: The source of variation observed among members of the same inbred strain reared under varying environmental conditions would likely be caused by the environmental factors, as the genetic factor is relatively constant within the inbred strain.

Step-by-step solution

Since inbred strains have a relatively homogeneous genetic background, the genetic variation within the strain would be minimal. #Step 2: Consider the changing factor - environment#

The question states that the environment is varying for individuals of the same inbred strain. #Step 3: Determine the impact of the environment on phenotypic variation#

The environment can affect the phenotype, or physical traits, of individuals in various ways, such as through the availability of resources, temperature, stress, etc. #Step 4: Conclude the source of variation among members of the same inbred strain#

Since the genetic factor is relatively constant within the inbred strain, and the environment is changing, the source of variation observed among members of the same inbred strain reared under varying environmental conditions would likely be caused by the environmental factors.

Key concepts

Genetic Factors in Phenotypic Variation

Understanding how our genes control our traits is a foundational element of genetics. Genetic factors refer to the inherited instructions that are carried within an organism's DNA and contribute directly to its physical characteristics, or phenotype. This information is often transmitted from parents to offspring through genes, which act as blueprints for a wide range of features, from eye color to potential risk for certain diseases.

In an educational context, we might discuss how identical twins, who share the same genetic makeup, often look very similar due to their genetic factors. However, even in such cases, tiny differences can occur, which is a testament to the complexity of genetic mechanisms. Genetic factors include not only the presence of specific genes but also their interaction with each other, known as epistasis, and the way genes are expressed, or gene expression. The examination of inbred strains, which have reduced genetic variation, aids in the clarity of the role of genes, as differences in phenotype can be more reliably attributed to genetic differences rather than environmental conditions.

Environmental Influences on Phenotype

While genetics provide the blueprint, the environment shapes the development and expression of an organism's traits. Environmental influences on phenotype cover a broad spectrum including diet, temperature, exposure to toxins, stress levels, and even social interactions, among other aspects. For instance, a plant's growth can be stunted by inadequate sunlight regardless of its genetic potential for height.

Students can easily relate to this concept by considering how their own height can be influenced by nutrition, despite the genetic component to stature. Variation in environments can lead to a wide variability in phenotypes among members of the same species, or even within a genetically similar group like an inbred strain. This adaptability is essential for survival, enabling organisms to optimize their fitness in response to changing environmental conditions.

Inbred Strains

Inbred strains are groups of organisms that are genetically very similar due to controlled breeding. Scientists create these strains by mating close relatives over several generations, which reduces genetic variation within the strain. This homogeneity makes inbred strains particularly useful in research to study the effects of genetic and environmental factors on phenotype.

Imagine that you are working with a group of laboratory mice that belong to the same inbred strain. If they are all raised under identical conditions and still show variation in a trait, that variation would be largely due to genetic differences. Conversely, if these genetically similar mice are raised in different environments, any phenotypic differences that arise can be attributed more to the environment than to genetics. This is due to the fact that genetic variation within such inbred populations is typically minimal. By studying inbred strains, scientists can better understand the specific roles and interplay of genetic and environmental factors in developmental processes.