Question

The observation that the mammalian Pax6 gene and the Drosophila eyeless gene are homologous genes that promote the formation of different types of eyes suggests that a. Drosophila eyes are more complex. b. mammalian eyes are more complex. c .eyes arose once during evolution. d .eyes arose at least twice during evolution. e .eye development is a simple process.

Short answer

The correct answer is (c). Eyes arose once during evolution.

Step-by-step solution

Understand the implication of homologous genes

The term 'homologous genes' refers to the genes in different species that are similar because they were inherited from a common ancestor. These genes often have similar functions. In this case, the Pax6 gene in mammals and the eyeless gene in Drosophila contribute to eye formation despite the differences in these organisms.

Analyze the answer choices

Options a and b focus on the complexity of eyes which isn't relevant to the discussion of homologous genes. Option e oversimplifies eye development which is not true. So, we can rule these out.

Interpret the evolutionary explanation

Options c and d pertain to evolution, which seems more relevant given the context of homologous genes. When two species have homologous genes for a similar function, it suggests that this trait arose just once in their common ancestor and was then passed down (option c). However, because the eyes of a mammal and a Drosophila are distinctly different, one might argue they could have evolved independently, suggesting eyes arose at least twice (option d). However, sharing a homologous gene implies a single origin.

Key concepts

Homologous Genes

The concept of homologous genes is pivotal in understanding the evolutionary relationships between different species. These genes are similar because they are derived from a common ancestor. When species diverge from a common lineage, their genes can continue to perform similar functions despite being in different organisms. For example:

• The Pax6 gene in mammals and the eyeless gene in Drosophila are considered homologous because they both play a crucial role in eye development.
• Despite variances in the structural complexity of the eyes they help form, their genetic similarity hints at shared evolutionary roots.

This notion provides evidence that complex structures like eyes may have developed a long time ago, in an ancient ancestor, before being passed down to varied species adapting to their unique environments.

Homologous genes, therefore, give us insight into the shared paths of evolution, highlighting both the unity and diversity of life on Earth.

Pax6 Gene

The Pax6 gene is a master control gene for eye development in mammals. It is famously known as a transcription factor, meaning it regulates the expression of other genes crucial for developing various parts of the body, particularly the eyes. Consider these interesting facts:

• Pax6 is integral not only for the initial formation of eyes but also influences aspects of the visual field and other sensory areas.
• Mutations in the Pax6 gene can lead to severe eye disorders in humans, such as aniridia, which can cause partial or complete absence of the iris.

This underscores the importance of Pax6 in ensuring the proper structural and functional development of eyes.

Through its highly conserved nature across different species, Pax6 illustrates the power of evolutionary genetics in maintaining essential biological processes.

Drosophila Eyeless Gene

The eyeless gene of Drosophila is the fruit fly's counterpart to the Pax6 gene in mammals. It plays a crucial role in the fly's eye development process. Here’s what makes the eyeless gene fascinating:

• Despite the significant differences between the mammalian and Drosophila eyes, the eyeless gene serves a similar functional purpose in eye formation.
• It demonstrates the concept of evolutionary conservation, where essential functions are upheld across diverse life forms for maintaining key biological features.
• Scientific experiments have showcased that inserting Pax6 into Drosophila can induce the formation of ectopic eyes, highlighting the deep evolutionary connection and versatility of this gene.

The Drosophila eyeless gene thus serves as an excellent case study for understanding how specific genes can bridge the evolutionary gap between vastly different species.

Genetic Inheritance

Genetic inheritance is a fundamental concept in biology that explains how traits and genetic information are passed from parents to offspring. This process forms the backbone of evolutionary theory and biodiversity. Let’s explore some of its key aspects:

• Inheritance involves the transmission of genes, which contain the genetic blueprint for various traits and biological functions.
• Through genetic recombination and mutations, offspring may have variations of traits not present in the parents, contributing to evolutionary adaptability.
• In the context of homologous genes like Pax6, genetic inheritance indicates that these traits arose in a common ancestor and were maintained through evolutionary history due to their crucial role in survival.

By understanding genetic inheritance, we grasp how complex structures, like eyes, can evolve once and then diversify across different species, showcasing the marvels of evolutionary mechanics.