Science and Creationism 14. Genetics © Colin Frayn,

© Colin Frayn, Junk DNA What is junk DNA for? –Less than 2% of DNA codes for proteins –Some of the rest has a purpose –Most appears to be completely useless Evolution explains this perfectly –DNA copying is a blind process –It can be hijacked, e.g. by viruses –It makes mistakes –Mistakes accumulate over (lots of) time Why would an omniscient designer create junk? –And why create the same junk in similar species?

© Colin Frayn, Endogenous Retroviruses An ERV is an ancient virus that “wrote itself” into our genome –It does this by hijacking our own molecular apparatus –Uses ‘reverse transcriptase’ This converts RNA of viruses into DNA We share several of these with our most recent evolutionary ancestors –There are several thousand in the human genome The more distant the ancestor, the fewer we have in common Individual ERVs are mutated over time –This gives another excellent genetic clock –Identify the same ERV in to species and count the differences –More differences = longer since last common ancestor

© Colin Frayn, Glutamic acid in Haemoglobin Alpha- and beta- chains of hemoglobin –These contain 12 codons for glutamic acid –Glutamic acid can be coded by either GAA or GAG They both mean the same thing All other things being equal, there’s no reason why to choose either over the other So… it’s amazing that in all 12 positions, human, chimpanzee and monkey DNA use exactly the same variants –Except, of course, this is exactly what evolution predicts –We shared a common ancestor –We inherited the same DNA

© Colin Frayn, Haemoglobin alpha chains This contains 141 amino acids –There are 20 to choose from so… –…probability against is 1: Is this massive number a disproof of evolution? No, because: –Evolution is not random Some strings are much more likely to evolve than others –Also, the current form is not the only plausible form In fact, there are an estimated usable forms So the probability of forming any one is 1:20 25 This is a certainty within evolutionary time In fact, the similarity of haemoglobin strings in humans and other primates is a very string evidence for evolution.

© Colin Frayn, Cytochrome C This is an enzyme It is found in all living creatures Differences (number of amino acids) in Cytochrome-C between humans and other organisms: Monkey1Chicken18 Dog13Penguin18 Horse17Turtle19 Donkey16Rattlesnake20 Pig13Fish (tuna)31 Rabbit12Fly33 Kangaroo12Moth36 Duck17Mold63 Pigeon16Yeast56