Comparing Humans and Chimps Photo:
Published online Dec Performed the computational anaylsis: Received Sep 30; Accepted Nov Copyright Lee et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited.
This article has been cited by other articles in PMC. Associated Data Table S1: Genomic positions of RRMI loci between human and chimpanzee lineages 0. Primer information for RRMI loci 0. Since the divergence of human and chimpanzee lineages, these elements have vigorously created chromosomal rearrangements causing genomic difference between humans and chimpanzees by either increasing or decreasing the size of genome.
Here, we report an exotic mechanism, retrotransposon recombination-mediated inversion RRMIthat usually does not alter the amount of genomic material present.
Through the comparison of the human and chimpanzee draft genome sequences, we identified inversions whose respective inversion junctions can clearly be characterized.
Our results suggest that L1 and Alu elements cause chromosomal inversions by either forming a secondary structure or providing a fragile site for double-strand breaks.
Among them, three RRMI loci inverted exonic regions in known genes, which implicates this mechanism in generating the genomic and phenotypic differences between human and chimpanzee lineages. This study is the first comprehensive analysis of mobile element bases inversion breakpoints between human and chimpanzee lineages, and highlights their role in primate genome evolution.
Among them are L1 and Alu elements, that have been active since well before the divergence of the human and chimpanzee lineages, and remain active in their host genomes. A full-length functional L1 element is about 6 kb in length and able to code for enzymes which are required for L1 retrotransposition, making the L1 an autonomous element .
By contrast, the Alu element is bp long and does not encode the means of its own retrotransposition, instead borrowing the enzymatic machinery of the L1 elements for its propagation making it a non-autonomous mobile element. L1 and Alu elements have played an important role in shaping their host genomes.
They can alter gene expression patterns and cause chromosomal rearrangements through various mechanisms including novel insertion, insertion-mediated deletion, and unequal homologous recombination between elements  — .
Sequence identity between two retrotransposons of the same type e. Such recombination can cause species-specific local genomic instability and has been reported as a major source of genomic disorders .
Inverted Alu and L1 pairs i. Due to their sequence similarity, they have the ability to form a hairpin structure in single-stranded DNA or a cruciform structure in double-stranded DNA .
These structures can potentially block progression of the replication fork and cause intra- or inter-molecular template switching of DNA polymerase between the inverted elements .
In reality, inverted Alu pairs cause a fold increase in homologous recombination . Here, we report for the first time a genome-wide analysis of retrotransposon recombination-mediated inversion RRMIcausing genomic and subsequently phenotypic differences between humans and chimpanzees.
The previously reported mechanism, Alu recombination-mediated deletion ARMDalters or interrupts gene function through the deletion of intronic and exonic regions.
By contrast, RRMI usually does not cause any change in genome size.To study the genomic divergences among hominoids and to estimate the effective population size of the common ancestor of humans and chimpanzees, we selected 53 autosomal intergenic nonrepetitive DNA segments from the human genome and sequenced them in .
While the genetic difference between individual humans today is minuscule – about %, on average – study of the same aspects of the chimpanzee genome indicates a difference of about %. The bonobo (Pan paniscus), which is the close cousin of chimpanzees (Pan troglodytes), differs from humans to the same degree. It has also been shown that the sequence divergence between DNA from humans and chimpanzees varies greatly. For example, the sequence divergence varies between 0% to % between non-coding, non-repetitive genomic regions of humans and chimpanzees. The DNA sequences of humans and chimpanzees are 98 percent identical. Yet that 2 percent difference represents at least 15 million changes in our genome since the time of our common ancestor.
The popular understanding of the genetic differences between chimpanzees and humans should be recast in light of the findings of major differences in segmental duplications, said the senior author of the study, Evan Eichler of the Howard Hughes Medical Institute at .
Dec 29, · Since the divergence of human and chimpanzee lineages, these elements have vigorously created chromosomal rearrangements causing genomic difference between humans and chimpanzees by either increasing or decreasing the size of genome.
So the same gene can be turned up high in humans, but very low in chimps. The same genes are expressed in the same brain regions in human, chimp and gorilla, but in different amounts.
Thousands of differences like these affect brain development and function, and help explain why the human brain is larger and smarter. For example, the sequence divergence varies between 0% to % between non-coding, non-repetitive genomic regions of humans and chimpanzees.
The percentage of nucleotides in the human genome (hg38) that had one-to-one exact matches in the chimpanzee genome (pantro6) was %. Some assert that humans and chimpanzees are only 1 to 2% different, but careful re-tallying suggests there is a gigantic genetic gap between the two species.