PR13_Eukariontska genomika
Kompleksnost eukariontskih genomov
The ring of life hypothesis
Schematic representation of the flow of genetic material from the two major
prokaryotic groups into the base of the eukaryotes and the separate flow of
genetic material from cyanobacteria into plastid-containing eukaryotes.
Genome and gene sizes for a
representative set of genomes
Gene size is plotted as a function of
genome size for some representative
bacteria, fungi, plants and animals. This
figure illustrates a simple rule of thumb:
in general, bigger genomes have bigger
genes. Thus, accurate annotation of a
larger
genome
requires
a
more
contiguous genome assembly in order
to
avoid
splitting
genes
across
scaffolds. Note too that although the
human and mouse genomes deviate
from the simple linear model shown
here,
the
trend
still
holds.
Their
unusually large genes are likely to be a
consequence of the mature status of
their annotations, which are much more
complete
as regards
annotation of
alternatively spliced transcripts and
untranslated regions than those of most
other genomes.
Major component of eukaryotic
genomes are transposable elements
Assembly errors caused by repeats
A | Rearrangement assembly error caused by repeats. Aa | An
example assembly graph involving six contigs, two of which are
identical (R1 and R2). The arrows shown below each contig represent
the reads that are aligned to it. Ab | The true assembly of two contigs,
showing mate-pair constraints for the red, blue and green paired reads.
Ac | Two incorrectly assembled chimeric contigs caused by the
repetitive regions R1 and R2. Note that all reads align perfectly to the
misassembled contigs, but the mate-pair constraints are violated.
B | A collapsed tandem repeat. Ba | The assembly graph contains four
contigs, where R1 and R2 are identical repeats. Bb | The true assembly,
showing mate-pair constraints for the red and blue paired reads, which
are oriented correctly and spaced the correct distance apart. Bc | A
misassembly that is caused by collapsing repeats R1 and R2 on top of
each other. Read alignments remain consistent, but mate-pair distances
are compressed. A different misassembly of this region might reverse the
order of R1 and R2.
C | A collapsed interspersed repeat. Ca | The assembly graph contains
five contigs, where R1 and R2 are identical repeats. Cb | In the correct
assembly, R1 and R2 are separated by a unique sequence. Cc | The two
copies of the repeat are collapsed onto one another. The unique sequence
is then left out of the assembly and appears as an isolated contig with
partial repeats on its flank.
Težave pri sekveniranju in assemblyu
eukariontskih genomov
Zgodovina sekveniranja eukariontskih genomov I
Zgodovina sekveniranja eukariontskih genomov II
GOLD Eukaryotic genome projects (20.5. 2014):
total - 8143
,
genomes - 5562,
transcriptomes – 1044,
resequencing – 1387,
uncultured – 26
Complete: 2584,
Permanent draft: 859,
Draft: 643,
In progress: 4563
,
Targeted: 6.
Fungi: 3224 genomes
Metazoa: 1702
Plants: 1975
„Protists“: 570
A timescale of eukaryote evolution
Filogenija in evolucijski odnosi eukariontov
He et al. An alternative root for the eukaryote tree of life.
Curr Biol. 2014 Feb 17;24(4):465-470.
Rastlinski genomi
-Genomi rastlin, ki so pomembni za prehrano (žitarice: riž, koruza itd),
-orjaški genomi golosemenk (iglavcev)
-Genomi prvotnih kopenski rastlin,
-Genomi zelenih in rdečih alg.
Glivni genomi
-Genomi kvasovk,
-Genomi patogenih gliv,
-Genomi biotehnološko pomembnih gliv,
-Genomi najstarejših gliv so podobni živalskim genomom.
Živalski genomi
-Genom človeka,
-Genomi arhaičnih ljudi (Neandertalci in Denizovanci),
-Genomi primatov,
-Genomi različnih sesalcev,
-Genomi vretenčarjev (od piškurja do plazilcev/ptičev),
-Genomi nevretenčarjev,
-Najstarejši živalski genomi (spužve, ožigalkarji in rebrenjače).
Genomi „primitivnih“ eukariontov
-Genomi parazitov in patogenov,
-Genomi prostoživečih organizmov,
-Kaj je vseboval genom najstarejših/prvotnih eukariontov.
Rastlinski genomi
Norway
spruce
genome
sequenced: Largest ever to be
mapped
Genomi parazitov in patogenov
Kaj je vseboval genom najstarejših/prvotnih eukariontov
Narobe !!
Nov pogled, bolj pravilen
Cavalier-Smith T. Kingdoms Protozoa and Chromista
and the eozoan root of the eukaryotic tree. Biol Lett.
2010 Jun 23;6(3):342-345.
Stechmann A, Cavalier-Smith T. Rooting the eukaryote
tree by using a derived gene fusion. Science 2002 Jul
5;297(5578):89-91.
Genomi arhaičnih ljudi (Neandertalci in Denizovanci)
High-throughput sequencing of ancient DNA
A
schematic
representation
of
high-throughput
sequencing of DNA from fossil remains, here depicted
as a Neanderthal bone. The ancient DNA is first blunt-
end repaired, and then DNA adaptors are added to each
end. The final product, called the sequencing library,
serves as the input for various high-throughput
sequencing strategies and technologies. All ancient
DNA molecules in the library will be first amplified
using the adaptors as priming sites in PCR. Aliquots
that contain copies of all original ancient DNA
molecules can be directly sequenced on a high-
throughput sequencer (centre panel) or used in targeted
enrichment via array (left panel) or primer extension
capture (right panel) methods. The pie charts illustrate
the percentage of Neanderthal DNA obtained by each
of these approaches.
Distinguishing ancient from modern DNA
a | Estimating contamination with modern DNA
. Shown is a section of
an alignment of the complete mitochondrial DNA (mtDNA) genome
(total 16,570 positions) of an early modern human from the Kostenki site,
Russia31. The positions are based on the revised Cambridge reference
sequence (rCRS). The first line of the alignment shows the consensus
sequence obtained from 311 worldwide modern human mtDNAs. The
second line shows the consensus sequence for 10,664 mtDNA fragments
retrieved from the 30,000-year-old Kostenki early modern human bone.
To get an estimate of contamination with modern human DNA, positions
were identified where more than 99% of 311 modern human mtDNAs are
different from the Kostenki consensus sequence. All fragments that
overlap such a position (boxed) and are different from the Kostenki
consensus base are likely to be modern human contamination. Only one
fragment (indicated by an arrow) is inconsistent, suggesting a very low
level of contemporary modern human contamination (1 out of 16
fragments that overlap this position and 1 out of 77 for the complete
Kostenki mtDNA data set).
b | The spatial distribution of DNA degradation patterns that are
typical for ancient DNA, shown here for the mtDNA fragments from
the Kostenki early modern human.
The upper panel shows DNA
mismatches to a reference sequence for all ancient mtDNA fragments:
more than 40% of Cs are seen as Ts at the 5′ end of the mtDNA fragments
(left) and more than 40% of Gs are seen as As at the 3′ end (right). The
lower panel shows the base frequency of the reference sequence: left,
purines (A and G) are in high frequency one base pair upstream of the 5′
end of the start of the mtDNA sequence; right, pyrimidines (C and T) are
in high frequency one base pair downstream of the 3′ end of the mtDNA
sequence. The presence of such patterns can be used to test the
authenticity of ancient modern human DNA.
Clovis, with its distinctive biface, blade and osseous technologies, is the oldest widespread archaeological complex
defined in North America, dating from 11,100 to 10,700 14C years before present (BP) (13,000 to 12,600 calendar
years BP). Nearly 50 years of archaeological research point to the Clovis complex as having developed south of the
North American ice sheets from an ancestral technology. However, both the origins and the genetic legacy of the
people who manufactured Clovis tools remain under debate. It is generally believed that these people ultimately
derived from Asia and were directly related to contemporary Native Americans. An alternative, Solutrean,
hypothesis posits that the Clovis predecessors emigrated from southwestern Europe during the Last Glacial
Maximum. Here we report the genome sequence of a male infant (Anzick-1) recovered from the Anzick burial site
in western Montana. The human bones date to 10,705 ± 35 14C years BP (approximately 12,707–12,556 calendar
years BP) and were directly associated with Clovis tools. We sequenced the genome to an average depth of
14.4× and show that the gene flow from the Siberian Upper Palaeolithic Mal’ta population into Native
American ancestors is also shared by the Anzick-1 individual and thus happened before 12,600 years BP. We
also show that the Anzick-1 individual is more closely related to all indigenous American populations than to
any other group. Our data are compatible with the hypothesis that Anzick-1 belonged to a population directly
ancestral to many contemporary Native Americans. Finally, we find evidence of a deep divergence in Native
American populations that predates the Anzick-1 individual.
Rasmussen M, et al. The genome of a Late Pleistocene human from a
Clovis
burial
site
in
western
Montana.
Nature
2014
Feb
13;506(7487):225-229.
Genetska struktura človeških populacij
(Amerika, Azija, Afrika, Židi itd.)
Aplikacija genomskih raziskav za humano biologijo
Aplikacija genomskih raziskav za biologijo
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