Schlagwort-Archive: evolution

Paternal mitochondrial inheritance

So far I thought this is not happening in humans, but a  PNAS paper published this month shows it may be even a genetic trait as the authors found biparental mtDNA inheritance in 17 members in three multi-generation families.
There are around 50-75 mitochondria in a single sperm which appears to be a quite low number (∼0.1%) relative to the number maternal mitochondria.
This unexpected paternal origin of mtDNA raises questions how exactly paternal mtDNA can escape its normal fate of being eliminated from the embryo. Are paternal mitos just being diluted and there is much more (micro-)heteroplasmy than currently known?
I don’t know why the authors didn’t do formal linkage analysis. And I also don’t know if their conclusion is correct “that occasional paternal transmission events seem to have left no detectable mark on the human genetic record” not citing an 1996 PNAS paper

In the majority of mammals—including humans—the midpiece mitochondria can be identified in the embryo even though their ultimate fate is unknown. The “missing mitochondria” story seems to have survived—and proliferated—unchallenged in a time of contention between hypotheses of human origins, because it supports the “African Eve” model of recent radiation of Homo sapiens out of Africa.

In the age of single cell sequencing it may no more be adequate to believe in maternal inheritance alone.

New species alignment

The UCSC Genome Bioinformatics Group ( who is running one of my favorite websites ) just announced

After 15.4 years of CPU run-time in 9,905,594 individual ‘jobs’ and 99 cluster runs for lastz pair-wise alignment…we are excited to announce the release of a 100 species alignment on the hg19/GRCh37 human Genome Browser.
This new Conservation track shows multiple alignments of 100 species and measurements of evolutionary conservation using two methods (phastCons and phyloP) from the PHAST package. This adds 40 more species to the existing 60 species track on the mm10 mouse browser. For more information about the 100 species Conservation track, please see its description page.

Funny? Laughable? Ridiculous?

www.cell.com/current-biology shows humour

Human emotional expressions, such as laughter, are argued to have their origins in ancestral nonhuman primate displays. To test this hypothesis, the current work examined the acoustics of tickle-induced vocalizations from infant and juvenile orangutans, gorillas, chimpanzees, and bonobos, as well as tickle-induced laughter produced by human infants.

Why do we possess introns?

This seems to be a question with not so many good answers. “The origins of genome architecture” (Sinauer, 2007) has a nice chapter on “Genes in pieces” covering

  • the spliceosome fisson-fusion model: Did a single ancestral spliceosome diverge into different lineages or is there an endogeneous origin within a single species?
  • the introns early-introns late debate: Were introns present in the first prokaryotic cell or not?

Mechanisms about intron gain center about AGGT tetramer duplication that result in new splice sites —AG|gt … ag|GT— with the segment in lower cases being the new intron. (What I found a funny fact, when working for the first time with genomic sequences around 1994 is the “codon ignorance” and “domain ignorance” of introns while on the other hand allowing for alternative splicing). Another mechanism of intron gain may be transposable elements although retrotransposons cannot deliver introns as they are spliced out. More likely are already released introns and ectopic reintegration. Another (not mentioned mechanism) could be random mutations activating cryptic splice sites.
The key question remains Why do we possess introns? weiterlesen