Genomes and Their Evolution

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Slide 52

Fig. 21-10b

(b) The human -globin and -globin gene families

Heme

Hemoglobin

-Globin

-Globin

-Globin gene family

-Globin gene family

Chromosome 16

Chromosome 11

2

1





2

1





G

A







Embryo

Embryo

Fetus

Fetus

and adult

Adult

Slide 53

Concept 21.5: Duplication, rearrangement, and mutation of DNA contribute to genome evolution

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

The earliest forms of life likely had a minimal number of genes, including only 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

Slide 54

Duplication of Entire Chromosome Sets

Accidents in meiosis can lead to one or more extra sets of chromosomes, a condition known as polyploidy

The genes in one or more of the extra sets can diverge by accumulating mutations; these variations may persist if the organism carrying them survives and reproduces

Slide 55

Alterations of Chromosome Structure

Humans have 23 pairs of chromosomes, while chimpanzees have 24 pairs

Following the divergence of humans and chimpanzees from a common ancestor, two ancestral chromosomes fused in the human line

Duplications and inversions result from mistakes during meiotic recombination

Comparative analysis between chromosomes of humans and 7 mammalian species paints a hypothetical chromosomal evolutionary history

Slide 56

Fig. 21-11

Human chromosome 16

Blocks of DNA

sequence

Blocks of similar sequences in four mouse chromosomes:

7

8

16

17

Slide 57

The rate of duplications and inversions seems to have accelerated about 100 million years ago

This coincides with when large dinosaurs went extinct and mammals diversified

Chromosomal rearrangements are thought to contribute to the generation of new species

Some of the recombination “hot spots” associated with chromosomal rearrangement are also locations that are associated with diseases

Slide 58

Duplication and Divergence of Gene-Sized Regions of DNA