They found that 59% of deserts overlapped with such areas, while only 12% of jungles overlapped.Ĭan sequence characteristics predict jungles and deserts? In general, the researchers found more simple repeats but not more genes or SNPs in jungles. The researchers looked at 55 inbred strains for places with little historical recombination. In HS and RI together, they found a total of 494 regions in which recombination rates were uncharacteristically high (which they termed “jungles”) or low (“deserts”). Intrigued by the incongruity in recombination, the researchers decided to look further into how rates vary with specific DNA features. The researchers also found many individual areas along the chromosomes that showed high recombination rates in one sex but not the other. Distribution of recombination frequencies differed with sex, too, with recombination higher near the junctures of the sister chromosomes (centromeres) in females and higher near telomeres in males. Calculating rates separately for male and female HS mice, the researchers found, as previous studies had found in humans, that the average autosomal (non–sex chromosomes) recombination rate for females was higher than that for males. There was also a sex difference in recombination rates. Genetically heterogeneous mice, derived from eight inbred strains, were used at the 50th generation for genetic mapping. And when they looked at variation in recombination rate along the chromosome, the researchers found the highest recombination rate near the ends of the chromosomes (on structures called telomeres). There was also a difference between the study groups: the HS genome showed a higher recombination rate in big chromosomes and a lower rate in small chromosomes than did the RI genome.
Smaller chromosomes, for instance, had a higher average recombination rate than larger ones. But the recombination rate varied substantially from one part of the genome to another. For HS, the average recombination rate was 0.63 cM per megabase (cM/Mb), and for RI, it was 0.62 cM/Mb. Using this process, they were able to create genetic maps of the mouse genome that can distinguish between two points 0.37 cM (centiMorgans, a measure of relative distance based on recombination frequency) apart in HS and 0.45 cM apart in RI-far more finely tuned than the best previous map.Īfter developing the super maps, the researchers used them to study recombination rates of various genes by comparing genetic and physical distances.
#Mouse distance measurer on a map software#
The researchers looked at the patterns of inheritance of 10,202 SNPs in HS animals and 11,609 SNPs in RI animals, then used special software to calculate their relative location based on how likely they are to occur together.
#Mouse distance measurer on a map code#
Physical mapping of the mouse genome has revealed the location of thousands of single nucleotide polymorphisms (SNPs)-stretches of DNA whose genetic code differs from one animal to another (or one homologous chromosome to another) by only one nucleotide base and that can be used as landmarks in the mapping process. To create the high-resolution map, the researchers used two groups of mice, one consisting of outbred, heterogeneous stock (HS) and the other of recombinant inbred lines (RI). Now, Sagiv Shifman, Jonathan Flint, and colleagues have provided a powerful new tool for genetic studies with the development in mice of the most detailed genetic map available for any species but humans. Because the mouse is a widely used model for genetic research, such capabilities would be invaluable. But these maps have lacked the resolution that investigators need to be able to do things like line them up against physical maps-the string of As, Gs, Cs, and Ts that gene sequencing supplies-to identify the precise location of genes, or explore the nuances of genetic recombination.
Genetic maps of the mouse genome-which identify the relative locations of specific stretches of DNA based on the likelihood of their being separated when chromosomes exchange parts during meiosis-work well for broadly defining where various points lie along a mouse’s chromosomes.
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