T 5/5 exam #3 (bring cheat sheet)T 5/5 exam #3 (bring cheat sheet)

Sat. 5/9 optional final exam, 9am-noonSat. 5/9 optional final exam, 9am-noon

Evolution: A species’ genetic component changes as the individuals reproduce. These changes are based on how the DNA changes and who reproduces.

How are we related, and where did we come from?

What happened to the Neanderthals?

http://youtube.com/watch?v=IsSOcwY79ig

What happened to the Neanderthals?

•Analysis of one million base pairs of Neanderthal DNA: “We have identified a 38,000-year-old Neanderthal fossil that is exceptionally free of contamination from modern human DNA.”

•Genetic evidence and the modern human origins debate: “At present, it is difficult to distinguish between a model of total genetic replacement and a model that includes some degree of genetic mixture.”

•No Evidence of Neandertal mtDNA Contribution to Early Modern Humans: “In combination with current mtDNA data, this excludes any large genetic contribution by Neandertals to early modern humans, but does not rule out the possibility of a smaller contribution.”

•A 28,000 Years Old Cro-Magnon mtDNA Sequence Differs from All Potentially Contaminating Modern Sequences: “The Paglicci 23 individual carried a mtDNA sequence that is still common in Europe, and which radically differs from those of the almost contemporary Neandertals, demonstrating a genealogical continuity across 28,000 years, from Cro-Magnoid to modern Europeans.”

Tbl. 1 Serre D, Langaney A, Chech M, Teschler-Nicola M, Paunovic M, et al. (2004) No Evidence of Neandertal mtDNA Contribution to Early Modern Humans. PLoS Biol 2(3): e57

PCR of mtDNA from fossils

Fig. 3 Serre D, Langaney A, Chech M, Teschler-Nicola M, Paunovic M, et al. (2004) No Evidence of Neandertal mtDNA Contribution to Early Modern Humans. PLoS Biol 2(3): e57

The four upper DNA sequences were determined in this study. Previously determined DNA sequences are shown below.

Comparisons of modern human and Neanderthal mtDNA sequences

Fig. 1 Neanderthals in central Asia and Siberia. J Krause, L Orlando, D Serre, B Viola, K Prüfer, M Richards, J Hublin, C Hänni, A Derevianko, S Pääbo (18 October 2007) Nature 449, 902-904

Known fossil range of Neanderthal

Extension of range

via mtDNA

Fig. 1 Analysis of one million base pairs of Neanderthal DNA. R Green, J Krause, S Ptak, A Briggs, M Ronan, J Simons, L Du, M Egholm, J Rothberg, M Paunovic, S Pääbo Nature (16 November 2006) 444, 330-336

Contamination of Neanderthal fossils with modern DNA

Fig. 5 Analysis of one million base pairs of Neanderthal DNA. R Green, J Krause, S Ptak, A Briggs, M Ronan, J Simons, L Du, M Egholm, J Rothberg, M Paunovic, S Pääbo (16 November 2006) Nature 444, 330-336

~8% of differences between human and chimp occurred since the divergence from Neanderthal

Fig. 6 Analysis of one million base pairs of Neanderthal DNA. R Green, J Krause, S Ptak, A Briggs, M Ronan, J Simons, L Du, M Egholm, J Rothberg, M Paunovic, S Pääbo (16 November 2006) Nature 444, 330-336

~6.5 million ya

~500,000 ya

How are we related, and where did we come from?

What happened to the Neanderthals?

Generation1

Generation3

Generation4

Generation5

Generation2

Mutation Replication Drift Selection

Mutations are subject to Drift and Selection

Evolution:A species’ genetic component changes as the individuals reproduce due to…

•Non-random changes (natural selection)•Random changes (genetic drift/bottleneck)

•Mutations add new alleles or genes

Endosymbiotic Theory – genes from mitochondria have migrated into the nucleus.About 90%+ of mt-proteins are nuclear encoded

Fig 7.20

Endosymbiotic Theory – genes from mitochondria have migrated into the nucleus.About 90%+ of mt-proteins are nuclear encoded

Fig 7.14

Human mtDNA,13 proteincoding genes

• Horizontal Gene Transfer–This is the exchange of genetic materials

among different species.• This is a common phenomenon• Occurs in many ways

–Prokaryotic cell may be engulfed by a eukaryotic cell

–Bacterial conjugation, transduction and transformation

»May account for 20-30% of variation in the genetic composition of modern prokaryotic species

http://biogetopics.wordpress.com/2008/11/

HGT mechanisms in prokaryotesFig 24.20

Bdelloid rotifers are small asexually reproducing freshwater invertebrates

Massive Horizontal Gene Transfer in Bdelloid Rotifers (May 2008)E. Gladyshev, M. Meselson, I. Arkhipova. Science 320: 1210 - 1213

In bdelloid rotifers we found many genes that appear to have originated in bacteria, fungi, and plants

Massive Horizontal Gene Transfer in Bdelloid Rotifers (May 2008)E. Gladyshev, M. Meselson, I. Arkhipova. Science 320: 1210 - 1213

Revised phylogenetic tree showing HGTFig 26.14

T 5/5 exam #3 (bring cheat sheet)T 5/5 exam #3 (bring cheat sheet)

Sat. 5/9 optional final exam, 9am-noonSat. 5/9 optional final exam, 9am-noon