DUPLICATIONS, REARRANGEMENTS, AND MUTATIONS OF DNA CONTRIBUTE TO GENOME EVOLUTION!

Namroo AnnapareddyWill ChenEsther Park

Overview

The basis of change at the genomic level is mutation Which underlies much of genome evolution

The earliest from of life likely had a minimal number of genes, including those necessary for survival and reproduction.

The size of genomes has increased over evolutionary time, with the extra genetic material providing raw material for gene diversification.

Duplication of Chromosome Set

Errors in Meiosis. Polyploidy : One or more extra sets of

chromosomes. This can cause new species and occurs often in plant

Mutations move on if the organism reproduces.

Duplication and Divergence of DNA segments

Errors in meiosis can lead to duplication of genes.

The transposable elements

provide sites where nonsister

chromatids can cross over. Slippage can occur during

DNA replication and can

cause a region to not be deleted

or copied twice.

The Human Globin Genes

Duplication events can lead to the evolution of genes with related functions.

Comparison of gene sequences in multigame family suggest the order.

All evolved from the same gene. After duplication arose mutations.

Evolution of Genes with Novel Functions

One copy of a duplicated gene can undergo alterations that lead to a new function for protein product.

Rearrangements of Parts of Genes: Exon Duplication and Exon Shuffling A exon within a gene could be

duplicated on one of the homologous chromosomes but deleted on the other.

The gene with the duplicated exon would code for a second protein containing the encoded domain and cause a structural change.

Exon shuffling.

Example of Exon Shuffling

An example would be TPA protein that is used for blood clotting. It has 4 domains and can hold three types. One exon would be duplicated to fill the forth domain.

 The three types are EGF ( Epidermal Growth Factor), Fibronectin gene, and Plasminogen gene.

The order they shuffle is unknown.

Exon Shuffling

Figure 19.20

EGF EGF EGF EGF

Epidermal growthfactor gene with multipleEGF exons (green)

F F F F

Fibronectin gene with multiple“finger” exons (orange)

Exonshuffling

Exonduplication

Exonshuffling

K

F EGF K K

Plasminogen gene with a“kringle” exon (blue)

Portions of ancestral genes TPA gene as it exists today

The transposable elements can contribute to the evolution of the genome.

The presence of homologous transposable elements sequences scattered throughout the genome allow recombination.

The movement of transposable elements around the genome can have several direct consequences.

Transposable elements can lead to new coding sequences.

Over long periods of time, the generation of genetic diversity provides more raw material for natural selection to work on during evolution.

Any

Questions??