Evolution by Gene Duplication

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Questions and Answers

What happens to the duplicated copy of an essential gene over extended periods of time?

It acquires many mutational changes

Why are unique genes not free to accumulate mutations and give rise to new genes, according to Ohno's thesis?

Because they are indispensable to the survival of members of any species

What is the potential advantage of the new function acquired by a duplicated gene?

It imparts an 'adaptive' advantage to organisms, enhancing their fitness

What is the primary mechanism hypothesized to be the source of new genes, according to Susumu Ohno's thesis?

Gene duplication Signup and view all the answers

What is the evidence that supports Ohno's thesis?

The discovery of genes with similar DNA sequences but distinct gene products Signup and view all the answers

What is the role of the original gene in Ohno's thesis?

It provides the genetic information for its essential function Signup and view all the answers

What is the time frame over which the duplicated gene may change sufficiently to assume a divergent role?

Long evolutionary periods Signup and view all the answers

What is the significance of gene duplication in the context of evolution?

It provides a mechanism for sustained genetic variability Signup and view all the answers

What is the evolutionary process by which related genes arise from a common ancestral gene?

Gene duplication Signup and view all the answers

What is the term used to describe groups of contiguous genes that perform similar functions?

Gene families Signup and view all the answers

What is the significance of the SRGAP2 gene in primates?

It provides evidence for gene duplication, with humans having multiple copies and nonhuman primates having only one copy. Signup and view all the answers

What is the term used to describe variations in the number of copies of a DNA sequence within a species?

Copy number variations (CNVs) Signup and view all the answers

What is the estimated percentage of the human genome occupied by CNVs?

5-10% Signup and view all the answers

What is the role of CNVs in the expression of individual traits?

They play a crucial role in both normal and diseased individuals Signup and view all the answers

What is the size range of CNVs that are typically considered in genomic studies?

50 bp to 3 Mb Signup and view all the answers

What is the significance of studying CNVs in genetics?

They are believed to play a crucial role in the expression of many traits and diseases Signup and view all the answers

Study Notes

Gene Duplication and Evolution

The process of gene duplication is hypothesized to be the major source of new genes, as proposed by Susumu Ohno in 1970.
Ohno's thesis suggests that essential genes are not free to accumulate mutations to alter their primary function and give rise to new genes, but duplicated copies can tolerate major mutational changes.

Mechanism of Gene Duplication

Gene duplication occurs in the germ line, resulting in an extra copy of the gene that can acquire many mutational changes over time.
The original gene provides the genetic information for its essential function, allowing the duplicated copy to change sufficiently to assume a divergent role in the cell.
Over long evolutionary periods, the duplicated gene may impart an "adaptive" advantage to organisms, enhancing their fitness.

Examples of Gene Duplication

The genes encoding digestive enzymes trypsin and chymotrypsin are examples of genes that have a substantial amount of their DNA sequence in common but have distinct gene products.
The genes encoding respiratory molecules myoglobin and hemoglobin are also examples of genes that arose from a common ancestral gene through duplication.

Gene Families

Gene families are groups of contiguous genes whose products perform the same or very similar functions.
Members of a family show DNA sequence homology sufficient to conclude that they share a common origin and arose through gene duplication.

Copy Number Variations (CNVs)

CNVs are duplications of large DNA sequences, often involving thousands of base pairs, that occur on a regular basis.
They represent quantitative differences in the number of DNA sequences and are found in both coding and noncoding regions of the genome.
CNVs are believed to play crucial roles in the expression of many individual traits, in both normal and diseased individuals.
They occupy between 5-10% of the human genome, with sizes ranging from 50 bp to 3 Mb.

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Description

Explore the mechanisms of genetic variation, particularly the origin of new genes through gene duplication, as proposed by Susumu Ohno in his monograph.