Question

A gene family includes a. one specific gene found in several different species. b. all of the genes on the same chromosome. c. two or more homologous genes found within a single species. d. genes that code for structural proteins. e. both a and c.

Short answer

The correct answer is e. 'both a and c'.

Step-by-step solution

Defining Gene Family

A 'gene family' is a set of several similar genes, formed by duplication of a single original gene, and generally with similar biochemical functions. They can belong to the same organism or to different species.

Analyzing Each Option

Option a. refers to one specific gene found in different species which is correct part as gene family can have genes from different species. However, the question specifies 'one' gene which is not entirely correct as a gene family typically includes multiple similar genes. Option b. is incorrect as gene family does not necessarily refer to all the genes on the same chromosome.Option c. is correct as gene family can consist of two or more homologous genes found within a single species.Option d. is incorrect as gene family does not exclusively consist of genes that code for structural proteins, it can include a variety of genes with similar biochemical functions.Option e. suggests that both a and c are correct. As analyzed, both these options are partially correct.

Best Answer

Option e. 'both a and c' is the most suitable choice. It takes into account that a gene family can include one specific (or typically, similar) gene found in several different species and two or more homologous genes within the same species.

Key concepts

Genetic Duplication

Genetic duplication is a fundamental concept in genetics, where a segment of DNA containing a gene is copied or duplicated. This process can occur naturally during cell division, particularly during DNA replication, or as a result of environmental stresses which may cause the DNA to break and repair itself imperfectly.

Over time, these duplicated genes can acquire mutations, leading to slight variations in their sequences. These variations allow the duplicated genes to potentially evolve new functions, which can be beneficial for the organism's adaptability and survival. An important notion to remember is that genetic duplication is essential for the development of gene families, as it establishes the basis for the existence of homologous genes within an organism or across different species.

Duplicated genes can remain on the same chromosome, close to the original gene, or they can be translocated to different chromosomes. Over evolutionary time scales, some duplicates may lose their function (become 'pseudogenes'), while others may evolve divergent, but still vital roles in the organism's physiology.

Homologous Genes

Homologous genes play a pivotal role in the concept of gene families. These genes share a common ancestry, meaning they typically originate from the same ancestral gene. There are two types of homologous genes: orthologous and paralogous genes.

Orthologous genes are homologous genes found in different species that evolved from a common ancestral gene after speciation (i.e., the formation of new and distinct species in evolution). Despite being separated by speciation, orthologs often retain similar functions.

On the other hand, paralogous genes are homologous genes that are found within the same species resulting from genetic duplication, and while they may retain related functions, paralogs often evolve new functions. Understanding homologous genes allows scientists to trace the evolutionary history of genetic material and to anticipate the functions of newly discovered genes based on their similarity to known genes.

Biochemical Functions

When discussing gene families, it's essential to delve into the biochemical functions these genes perform. Biochemical functions refer to the roles and activities of proteins or enzymes encoded by genes at the molecular level within an organism's body. This can include a variety of roles such as metabolism regulation, DNA replication, or cellular signaling.

Within a gene family, members often have similar biochemical functions, but minor differences in their sequences can lead to variations in how effectively they perform these functions, or result in slightly different activities. This functional diversification is key to the organism's ability to adapt to changing environments and to evolve new characteristics. For example, in a gene family responsible for detoxification, one member might be tuned to detoxify a specific toxin, while another closely related gene might be slightly less effective at this task but able to handle a broader range of toxic substances.

The study of the biochemical functions of gene family members contributes significantly to the understanding of how organisms live and respond to their environment, making it a crucial research field in biochemistry and genetics.