Which of the following provides the strongest evidence for the conservation of tool-kit genes?
a. Bicoid moved from one fly embryo into the posterior of another fly embryo causes the formation of two head regions.
b. Mutation of an unrelated gene in another species of fly has a similar effect to mutation of bicoid in Drosophila.
c. A mouse Hox gene can be used to take over the function of a mutated Drosophila Hox gene.
d. Sheep can be cloned by fusing a differentiated adult cell with an enucleated egg.

Verified step by step guidance

1. Understand the concept of tool-kit genes: Tool-kit genes are a set of genes that control the development of an organism's body plan. They are highly conserved across different species, meaning they have remained relatively unchanged throughout evolution.
2. Analyze option a: This option describes an experiment involving the bicoid gene, which is a tool-kit gene in flies. Moving bicoid from one embryo to another and causing the formation of two head regions demonstrates its role in development but does not directly show conservation across species.
3. Analyze option b: This option involves a mutation in an unrelated gene in another species of fly having a similar effect to a mutation in bicoid in Drosophila. This suggests functional similarity but not necessarily conservation of tool-kit genes across different species.
4. Analyze option c: This option describes a mouse Hox gene taking over the function of a mutated Drosophila Hox gene. Hox genes are a type of tool-kit gene, and this cross-species functionality strongly indicates conservation of these genes across different organisms.
5. Analyze option d: This option involves cloning sheep, which is a process of creating a genetically identical organism. While it involves genetic manipulation, it does not directly relate to the conservation of tool-kit genes across species.

Key Concepts

Tool-kit Genes

Tool-kit genes are a set of genes that control the development of an organism's body plan and structure. These genes are highly conserved across different species, meaning they have remained relatively unchanged throughout evolution. Their conservation suggests a fundamental role in developmental processes, allowing for the study of genetic functions across diverse organisms.

Hox Genes

Hox genes are a subset of tool-kit genes that determine the identity and arrangement of body segments along the anterior-posterior axis in animals. They are crucial for proper development and are conserved across many species, from fruit flies to mammals. The ability of a mouse Hox gene to substitute for a Drosophila Hox gene highlights their functional conservation and interchangeability across species.

Gene Conservation

Gene conservation refers to the phenomenon where certain genes remain unchanged across different species over evolutionary time. This conservation indicates that these genes perform essential functions that are critical for survival and development. Evidence of gene conservation can be seen when genes from one species can functionally replace similar genes in another species, demonstrating their universal role in biological processes.