Human lineage

the Human lineage

or how sequencing the genome of fossils of our extinct ancestors can help us understand our evolution and the human lineage

But first, meet the folks

And another one

Take a closer look at that Siberian cave to see what they found...

The Siberian cave (Denisova cave) where a fossil was found.

They found ... a very tiny piece of bone...

disappointed???

Let's see how can help in this matter...

Let's see how Genomics helps uncover the history of our ancestors...

DNA is extracted from fossils, but the fragments, often damaged, are too small to be of any help. This DNA can be nuclear DNA or mitochondrial DNA (often more preserved and easier to find). They are amplified by PCR and sequenced.

Let's see what our fossil mt DNA has in store...

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Now that we have the sequence, let's compare it to mtDNA from Homo species to establish evolutionary relationships

the result of the sequencing

By comparing DNA sequences, researchers can build a phylogenetic tree that shows how all the different sequences are likely related to each other. Each node of the tree represents a common ancestor. It shows the relationships among genes, and in some way among species (but not exactly because fossils come from specific individuals whereas we speak of species for a whole population of different individuals). The more similar DNA sequences are, the closer the species.

phylogene

geniegen2 or anagene

2 ways to compare sequences

Whatever the comparative method used, would you say that the denisova fossil is just another Neanderthal or Sapiens or a different Homo species?

Now that we have the sequence, let's compare it to mtDNA from Homo species to establish evolutionary relationships

the result of the sequencing

By comparing DNA sequences, researchers can build a phylogenetic tree that shows how all the different sequences are likely related to each other. Each node of the tree represents a common ancestor. It shows the relationships among genes, and in some way among species (but not exactly because fossils come from specific individuals whereas we speak of species for a whole population of different individuals). The more similar DNA sequences are, the closer the species.

phylogene

geniegen2 or anagene

2 ways to compare sequences

Whatever the comparative method used, would you say that the denisova fossil is just another Neanderthal or Sapiens or a different Homo species?

Utiliser les fonctionnalités du logiciel et la fiche technique pour comparer les séquences.Séquences: D-loop d’un humain actuel, du denisovien de la cave, d’un néanderthal et d’un chimpanzé. -> Calculer les % de similitudes entre chacun de ces gènes. Construisez un arbre de parenté où la distance de branche entre 2 individus est proportionnelle à leur degré d’homologie.

Sequences in Geniegen2

Info geniegen

Info ARBRE

Choisis la collection Homininés (une sous-famille qui regroupe gorilles, hommes et chimpanzés).

Clique sur fichier pour pouvoir charger les séquences à comparer

Clique sur fichier de molécules

Et choisis le fichier "lignee humaine et chimpanzés.aln"

Sélectionne dans la matrice de séquences: 3 Homo sapiens (Italien1, Français, Néerlandais), 3 Néanderthaliens (CROATIE, VINDIJA, ELSIDRON), 1 Dénisovien (DENISOVA) et un Singe Bonobo (PAN_PANISCUS).

Clique sur Matrice des Distances pour faire apparaitre les différences de nucléotides (en %) entre ces séquences.

L'avantage de Phylogène par rapport à Geniegen2, c'est que le logiciel construit directement l'arbre phylogénétique. Clique sur Arbre pour l'afficher.

Now answer the previous question: would you say this denisova fossil is just another Neanderthal or Sapiens, or a different Homo species?