1. 1 Chromosome Evidence for Ancestry © 2008 Regents of the University of California. All rights reserved. Use for SGI Field Test only.

2. 2 Tree hypothesis #1 based on hemoglobin protein evidence © 2008 Regents of the University of California. All rights reserved. Use for SGI Field Test only.

3. 3 Chromosome Numbers Chromosome number Human46 Chimpanzee (Pan troglodytes) 48 Gorilla (Gorilla gorilla) 48 Orangutan (Pongo abelii, Pongo pygmaeus) 48 © 2008 Regents of the University of California. All rights reserved. Use for SGI Field Test only.

4. 4 Based on the chromosome data, there are two possible hypotheses: Hypothesis One: If the four species share a common ancestor, that ancestor had 46 chromosomes. © 2008 Regents of the University of California. All rights reserved. Use for SGI Field Test only.

5. 5 Evidence for Hypothesis #1: Two chromosomes that were fused in the common ancestor split in the apes, and then fused again in the humans. © 2008 Regents of the University of California. All rights reserved. Use for SGI Field Test only.

6. 6 Would this evidence be consistent with the tree? Not really. Why would two chromosomes be fused in a common ancestor, split in the apes, and then re- fuse in the humans? © 2008 Regents of the University of California. All rights reserved. Use for SGI Field Test only.

7. 7 Hypothesis #2: The common ancestor had 48 chromosomes. © 2008 Regents of the University of California. All rights reserved. Use for SGI Field Test only.

8. 8 Evidence for Hypothesis Two: Two chromosomes were split in the common ancestor, remained split in the apes, and then fused in the human lineage. © 2008 Regents of the University of California. All rights reserved. Use for SGI Field Test only.

9. 9 Would this evidence be consistent with the tree? Yes. It would make sense that two split chromosomes in the common ancestor would remain split in the ape lineage, and then became fused in the human lineage. © 2008 Regents of the University of California. All rights reserved. Use for SGI Field Test only.

10. 10 How could evidence be gathered in order to test the two hypotheses? Sequence the chromosomes and reference a map of the genomes of humans and apes. © 2008 Regents of the University of California. All rights reserved. Use for SGI Field Test only.

11. 11 Published Findings The scientist later published a paper of his findings. The following quote is from his paper: “Chromosome 2 is unique to the human lineage of evolution, having emerged as a result of head-to-head fusion of two…chromosomes that remained separate in other primates. The precise fusion site has been located…” (Hiller et al (2005) “Generation and Annotation of the DNA sequences of Human Chromosomes 2 and 4,” Nature 434: 724-731.) © 2008 Regents of the University of California. All rights reserved. Use for SGI Field Test only.

12. 12 Figure 1: The chromosomes © 2008 Regents of the University of California. All rights reserved. Use for SGI Field Test only.

13. 13 Which hypothesis, one or two, do the published data in the journal support? Explain. © 2008 Regents of the University of California. All rights reserved. Use for SGI Field Test only.