Genomes and Their Evolution

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Abdomen

Slide 87

Sometimes small changes in regulatory sequences of certain genes lead to major changes in body form

For example, variation in Hox gene expression controls variation in leg-bearing segments of crustaceans and insects

In other cases, genes with conserved sequences play different roles in different species

Slide 88

Comparison of Animal and Plant Development

In both plants and animals, development relies on a cascade of transcriptional regulators turning genes on or off in a finely tuned series

Molecular evidence supports the separate evolution of developmental programs in plants and animals

Mads-box genes in plants are the regulatory equivalent of Hox genes in animals

Slide 89

Fig. 21-UN1

Bacteria

Archaea

Genome

size

Number

of genes

Gene

density

Most are 1–6 Mb

1,500–7,500

Higher than in eukaryotes

Introns

None in

protein-coding

genes

Other

noncoding

DNA

Very little

Present in

some genes

Can be large amounts;

generally more repetitive

noncoding DNA in

multicellular eukaryotes

Unicellular eukaryotes:

present, but prevalent only

in some species

Multicellular eukaryotes:

present in most genes

Lower than in prokaryotes

(Within eukaryotes, lower

density is correlated with

larger genomes.)

5,000–40,000

Most are 10–4,000 Mb, but

a few are much larger

Eukarya

Slide 90

Fig. 21-UN2

Slide 91

Fig. 21-UN3

Slide 92

You should now be able to:

Explain how linkage mapping, physical mapping, and DNA sequencing each contributed to the Human Genome Project

Define and compare the fields of proteomics and genomics

Describe the surprising findings of the Human Genome Project with respect to the size of the human genome

Distinguish between transposons and retrotransposons

Slide 93

Explain how polyploidy may facilitate gene evolution

Describe in general terms the events that may have led to evolution of the globin superfamily

Explain the significance of the rapid evolution of the FOXP2 gene in the human lineage

Provide evidence that suggests that the homeobox DNA sequence evolved very early in the history of life