For this assignment, we will consider a protein expressed in theliver of an African cheetah (Acinonyx jubatus). Biochemistsdetermined that this protein is involved in the production ofglycogen.
In a stunning announcement, a snowboarder in Antarctica claimsto have found a new species of cheetah that is able to survivefreezing temperatures and a long, dark winter. The snowboarderdescribed a slow, fat, white-furred cheetah that may be related tothe African cheetah. Scientists isolated a fragment of DNA from theobese feline creature which codes for the liver protein:
(3' end) ...CTACGTTCAGCTTGTCACGACTGGTTA... (5' end)
(5' end) ...GATGCAAGTCGAACAGTGCTGACCAAT... (3' end)
At almost the same time, a sleek, fast, white-coated cheetah wasfound in the Andes in South America where cheetahs were not knownto exist. With some difficulty, a geneticist convinced the cheetahto allow her to swab the inside of the big cat's cheek to get asample of DNA. Soon after, the geneticist was able to isolate thefollowing DNA fragment believed to be involved with glycogenproduction in the liver:
(3' end) ...TCACCTACGTTCAATAGGTCACGACTGG... (5' end)
(5' end) ...AGTGGATGCAAGTTATCCAGTGCTGACC... (3' end)
The original African cheetah DNA fragment describing the liverprotein in question is this:
(3' end) ...CACCTACGTTCAGGAGGTCAGGACTGGTTA... (5' end)
(5' end) ...GTGGATGCAAGTCCTCCAGTCCTGACCAAT... (3' end)
You are part of a team of geneticists, evolutionary biologists,and bioinformatics experts. You will attempt to describe thedifferences between the three species of cheetah in both geneticand evolutionary terms.
1)For each DNA sequence, transcribe to mRNA and then find thechain of amino acids that it produces. Remember that a gene mustbegin with the "Start" codon.
2)Describe the differences in the basic genetic code between thethree species. How many DNA point mutations would be required tochange from one species to the others? How do the amino acidsequences of the proteins differ? Are there any silent mutationsthat may not effect the function of the protein?
3)Looking at the amino acid substitutions that exist between thespecies, would you expect there to be large functional differencesbetween the two slightly different proteins based on the propertiesof the substituted amino acids? Explain why you think this might bethe case.
4)Quantitatively assess the evolutionary distance between eachpair of the three species using the substitution matrix and PAMscores. (This involves three pairs: African/Andes,African/Antarctic, and Antarctic/Andes.)
5)Propose a scenario describing how the two new cheetah speciesmight have evolved from the African cheetah. Were the two newcheetahs once a single species which then branched to form twoseparate species? Or did they evolve independently from the Africancheetah? Be sure to include in your scenario how the new cheetahsmanaged to move from Africa to their present locations. Estimate arelative time line for each separate speciation event. (Aspeciation event is the genetic or environmental event that resultsin the creation of a new species.) How might the three proteinsexplain the survivability of the three species in their nativehabitat? (A little speculation is OK here. You are presenting ahypothesis based on the available evidence. Further research wouldbe required to prove your hypothesis.)
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