Genomes and Their Evolution

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These inform us about relationships among species that diverged from each other a long time ago

Bacteria, archaea, and eukaryotes diverged from each other between 2 and 4 billion years ago

Highly conserved genes can be studied in one model organism, and the results applied to other organisms

Slide 73

Comparing Closely Related Species

Genetic differences between closely related species can be correlated with phenotypic differences

For example, genetic comparison of several mammals with nonmammals helps identify what it takes to make a mammal

Slide 74

Human and chimpanzee genomes differ by 1.2%, at single base-pairs, and by 2.7% because of insertions and deletions

Several genes are evolving faster in humans than chimpanzees

These include genes involved in defense against malaria and tuberculosis, regulation of brain size, and genes that code for transcription factors

Slide 75

Humans and chimpanzees differ in the expression of the FOXP2 gene whose product turns on genes involved in vocalization

Differences in the FOXP2 gene may explain why humans but not chimpanzees communicate by speech

Slide 76

Fig. 21-16

Wild type: two normal

copies of FOXP2

EXPERIMENT

RESULTS

Heterozygote: one copy

of FOXP2 disrupted

Homozygote: both copies

of FOXP2 disrupted

Experiment 1: Researchers cut thin sections of brain and stained

them with reagents, allowing visualization of brain anatomy in a

UV fluorescence microscope.

Experiment 2: Researchers sepa-

rated each newborn pup from its

mother and recorded the number

of ultrasonic whistles produced by

the pup.

Experiment 1

Experiment 2

Wild type

Heterozygote

Homozygote

Number of whistles

Wild

type

Hetero-

zygote

Homo-

zygote

(No

whistles)

0

100

200

300

400

Slide 77

Fig. 21-16a

EXPERIMENT

RESULTS

Wild type: two normal

copies of FOXP2

Heterozygote: one copy

of FOXP2 disrupted

Homozygote: both copies

of FOXP2 disrupted

Experiment 1: Researchers cut thin sections of brain and stained

them with reagents, allowing visualization of brain anatomy in a

UV fluorescence microscope.

Experiment 1

Wild type

Heterozygote

Homozygote

Slide 78

Fig. 21-16b

EXPERIMENT

RESULTS

Wild type: two normal

copies of FOXP2

Heterozygote: one copy