Comparative Analysis Of Microsatellite Sequences In Homo Sapiens And Pan Mitochondrial Genome

Microsatellite also known as simple tandem repeats simple sequence repeats(SSRs),is a repeat unit based on 1-6 base pairs of(bp)nucleotide s equences.SSRs are commonl y found in almost all of the genomes in the biolo gical world,and they exist in different functional areas of the entire genome for a given biological genome,including the expression region,the regulator y region,the junction region between genes and so on.Because of their high mutation rate and widespread distribution in the whole genome,microsate llites ma y significantly affect genome evolution through a variet y of mech anisms,including potential effects on recombination,regulation of gene e xpression,gene transforma tion and chromosomal organization.Microsatellite sequences are often used to stud y the phylogenetic relationships of species and the evolutionar y relationships among the genomes of closel y related sp ecies.The article was mainly carried on the research from two aspects :1.Microsatellite map of the whole mitochondrial genom ic sequence of Homo sapiens and Pan(Chapter 2)In this work,90 mitochondrial genome sequences were obtained from NCBI's genbank database,including 30 Homo sapiens from 30 different hapl otypes.Pan troglodytes and Pan paniscus were the closest species,30 samples from each of the two species,among which Pan paniscus data were obtained from different subspecies.In this paper,the microsatellite distribution of coding region and D-loop region were anal yzed.The anal ysis revealed that :(1)in the coding region and the D-Loop region,different genomic regions had different microsatellite distribution al characteristics,and different species also showed different microsatellite distributions in the same genomic region;(2)in the coding region,the difference s of microsatellite s were obvious in the first half of genomes,however,the difference s of microsatellite distribution among species were obscure in the second half of the genomes.The distrib utional frequency of mononucleotide microsatellites was the highest,dinucle otide microsatellites was followed,that of trinucleotide microsatellites was the lowest,and there was lack of tetranucleotide microsatellites;(3)in the DLoop region,microsatellites h ad the highest distribution at the region of 1-57 7 bp in the Homo sapiens mitochondrial genome,and the highest distribution of mononucleotide,dinucleotide,trinucleotide and tetranucleotide microsate llites were detected in this region.The most notable was that in the 600-800 bp,onl y Homo sapiens were detected to distribute microsatellites,while Pan paniscus was not discovered those special repeats,moreover,tetranucleotide microsatellites were distributed in all three species.This stud y revealed the distribution of microsatellites on the mitochondrial genomes of Homo sapiens and relative species,which can be used to further anal yze the correlation b etween microsatellites and the evolution of m itochondrial genomes.2.Structural and functional anal ysis of conserved microsatellite loci in Homo sapiens and Pan mitochondrial genome(Chapter 3)The preliminar y anal ysis of 90 mitochondrial genome microsatellite maps showed that there were man y very conservative microsatellite loci.In this work,31 conserved perfect microsatellite sites were found,and 19 conserved microsatellite sites on amino acid gene were selected to stud y the protein structure and function.The results show ed that:(1)the conserved microsate llite sequences in the mitochondrial genome were actuall y at the protein sites with important function;(2)these sites pla yed a ke y role in the formation of protein spatial structures b y connecting different t ypes of secondar y s tructures.In this chapter,it is found that the conserved microsatellite site s encode d the ke y amino acids of protein structure and function,which could not be mutated in the process of evolution.Conserv ed microsatellite sequences might be preserved without mutatio n over a long period of time.It ma y be that conserv ed perfect microsatellite sequences were preserved b y important structural and functional choices of proteins.In this paper,we use d biological databases and software to explore the distribution of microsatellites in the mi tochondrial genome and study the conserved microsatellite sites in detail.These conserved sites could be preserved because they encode d amino acids,which played a ke y role in the structure and function of proteins.