In lab we were able to study gene mutations an patterns of inheritance using the model organisms Caenorgabditis elegans commonly referred to as C elegans C elegans is a eukaryotic multicellular organism that shares cellular and molecular structures with higher organisms and undergoes complex developmental processes allowing the biological information we gather to be applied to more intricate organisms such as humans 1 The sex of the C elegans is determined by the ratio of sex chromosomes to autosomes If the sixth chromosome is an XX combination it is a hermaphrodite if the worm possesses a XO combination it is a male Hermaphrodites are the most common sex of these worms and have the ability to either self fertilize or mate with males 2 C elegans worms are often used in genetic research because a single worm can produce about 300 offspring making it easy to produce many genotypes and phenotypes This combined with their short life cycle makes them convenient for research We chose to observe worms with the mutation ROL 6 and determine whether the mutation was recessive or dominant We also planned to determine whether it was sexlinked or autosomal We chose to observe this mutation because we deemed that it would be easy to notice considering that worms with the ROL 6 mutation move in a circular formation unlike unaffected worms In order to determine the traits of this mutation we needed to produce offspring to observe Knowing that if we only allowed a hermaphrodite to self fertilize the offspring would be exact replicas we chose to cross a homozygous ROL 6 mutated hermaphrodite and a homozygous wild type unaffected male This cross would allow us to determine whether the mutation was dominant or recessive by looking at the ratio of mutant to normal offspring if the mutation was dominant 100 of the offspring would be mutated and if it was recessive 50 would be mutated If the mutation is sex linked all of the males offspring would be mutated and all of the hermaphrodites would be normal Recessive Sex Xa Xa Linked a a Recessive Autosoma XA XAXa X XAXXa l XOAA OAXa XAXa OAXXa AXa OA OAXa OAXa Dominant Sex Linked XA A XA Dominant Autosomal X XA a A a A a X X X X X a A a X X X XAXa Oa OaXA OaXA Oa OaXA OaXA We knew that by choosing the cross between the homozygous mutated hermaphrodite and the homozygous wild type male we would be able to tell if the mutation was dominant or recessive After placing both C elegans onto a petri dish using a sterilized worm spatula and allowing them to reproduce for one week we observed the offspring under a microscope We expected to see hundreds of offspring in the dish but unluckily all of our worms died We were able to look on with another group to observe what the more typical results should look like Their dish did indeed contain hundreds of C elegans so we decided to divide the dish into four quadrants We chose one quadrant to identify and count the number of males hermaphrodites and how many of which were mutated worms Males and hermaphrodites were distinguished from each other by differentiating the shapes of their tails Males possess a tail that has a rounded edge with a lip on the end while hermaphrodites tails are tapered and are much more skinny Our results were as follows Wild type male ROL 6 male ROL 6 hermaphrodite 8 16 24 Because the offspring were not 100 mutated we immediately know that the ROL 6 mutation is recessive Looking at the punnett squares for the possibilities of a recessive mutation the ratio of offspring could either turn out to be 100 unaffected or 50 mutated and 50 unaffected Our experiment yielded neither of these outcomes however these punnett squares do not take into consideration the offspring produced by the hermaphrodite through self fertilization which would produce mutated hermaphrodites In order to decide whether the mutation was sex linked or autosomal we needed to analyze the gender of the worms and how many of each was mutated The mutation seems to be sex linked considering that there are multiple normal males Therefore the mutation must be autosomal To prove our theory that the mutation is autosomal recessive we decided to do another crossing of a wild type hermaphrodite with a wild type male Assuming they are both F1 offspring from the crossing of the homozygous mutated hermaphrodite and the unaffected male they would both be heterozygous Therefore if we are correct their offspring would be 75 normal and 25 mutated We did two crossings to ensure accuracy in case we accidently misidentified a worm When we came back to the lab to observe the F2 offspring produced by our second crossing we were pleased to see that the offspring were conclusive with the results of our original observations The ratios were not exact but both normal and mutated worms were present proving to us that our initial inference was indeed correct Works Cited 1 C elegans as a Model System Waksman Student Scholars 9 April 2013 http avery rutgers edu WSSP StudentScholars project introduction worms html 2 A Model Experimental System The Properties of C elegans The Characteristics of C elegans That Make It Useful in Teaching 9 April 2013 http www nbr wisc edu outreach text celegans pdf