Short Tandem Repeat variation and its role in environmental adaptation
Anne Greulich, Biosciences
Today it is known that the genome of most organisms consists in large parts of repetitive DNA. The human genome for example is made up of 46% of repeats. In this context short tandem repeats (STRs), DNA sequences with a unit length of 1 to 9 nucleotides (nt) have emerged as possible genetic regulatory elements. An example for a TR is the sequence ACTGACTGACTG, where the unit ACTG consisting of four nucleotides is repeated three times. Compared to non-repeat parts of the genome STRs are highly unstable as they have mutation rates that can be 10 to 100 000 times higher and usually infer by replication slippage leading to a change in the number of repeat units (repeat polymorphism). This variation of repeat length is interesting to study as some pathogenic bacteria have been shown to use the variation in repeat length to switch on and off certain phenotypes and thereby escape the immune reaction of the host they are invading. The most important thing is that a variation in repeat length helps them adapt to a new environment. The main aim of my project is to show if and how short tandem repeat variation helps Thale cress (Arabidopsis thaliana) and Atlantic cod (Gadus morhua) adapt to the environment. A major goal is to compare repeat variation over several generations for both species to see if there are any changes that improve fitness. Candidate genes that show a repeat length variation over generations will then be used for functional studies.