Genomes and Their Evolution

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Errors in meiosis can result in an exon being duplicated on one chromosome and deleted from the homologous chromosome

In exon shuffling, errors in meiotic recombination lead to some mixing and matching of exons, either within a gene or between two nonallelic genes

Slide 66

Fig. 21-14

Epidermal growth

factor gene with multiple

EGF exons (green)

Fibronectin gene with multiple

“finger” exons (orange)

Exon

shuffling

Exon

shuffling

Exon

duplication

Plasminogen gene with a

“kringle” exon (blue)

Portions of ancestral genes

TPA gene as it exists today

Slide 67

How Transposable Elements Contribute to Genome Evolution

Multiple copies of similar transposable elements may facilitate recombination, or crossing over, between different chromosomes

Insertion of transposable elements within a protein-coding sequence may block protein production

Insertion of transposable elements within a regulatory sequence may increase or decrease protein production

Slide 68

Transposable elements may carry a gene or groups of genes to a new location

Transposable elements may also create new sites for alternative splicing in an RNA transcript

In all cases, changes are usually detrimental but may on occasion prove advantageous to an organism

Slide 69

Concept 21.6: Comparing genome sequences provides clues to evolution and development

Genome sequencing has advanced rapidly in the last 20 years

Comparative studies of genomes

Advance our understanding of the evolutionary history of life

Help explain how the evolution of development leads to morphological diversity

Slide 70

Comparing Genomes

Genome comparisons of closely related species help us understand recent evolutionary events

Genome comparisons of distantly related species help us understand ancient evolutionary events

Relationships among species can be represented by a tree-shaped diagram

Slide 71

Fig. 21-15

Most recent

common

ancestor

of all living

things

Billions of years ago

4

3

2

1

0

Bacteria

Eukarya

Archaea

Chimpanzee

Human

Mouse

0

10

20

30

40

50

60

70

Millions of years ago

Slide 72

Comparing Distantly Related Species

Highly conserved genes are genes that have changed very little over time