Comparison of the Human and Great Ape Chromosomes as Evidence for Common Ancestry
Chromosome Challenge Discussion
I've never seen a creationist respond to this challenge. I've personally posted it on several forums in several discussions, and I've seen it posed by others many times too. Those of you who think evolution has no supporting evidence: what's your explanation, eh?
Chromosome Challenge Discussion
Posted by scigirl on another forum
Long long ago, in a lab far far away, scientists figured out that chimpanzees have 24 chromosomes in their sperms and eggs, whereas humans only have 23. Therefore, these great scientists theorized that two of our chromosomes had fused together sometime in the recent past (aka million years ago.). Their theory made 3 predictions:
1) One of our chromosomes would look like two of the chimp chromosomes stuck together.
2) This same chromosome would have an extra sequence in it that looked like a centromere. Centromeres are the things in the middle that microtubules grab onto to divide a pair of chromosomes during mitosis.
3) It would also have telomeres (ends) but in the middle - and they would be in reverse order. Sort of like this:
ENDchromosomestuffDNEENDchromosomestuffDNE
See the "DNEEND" in the middle? That's what two telomeres would look like if two chromosomes were stuck together.
Lo and behold, these theories were put to the test. To test prediction 1, know that chromosomes all have a unique banding patttern. A "fingerprint." To test 2 and 3, you need sequence data. Telomeres and centromeres have characteristic DNA sequences.
What did those scientists find:
http://www.gate.net/~rwms/hum_ape_chrom_2.gif
H=human, C=chimp, G=George Bush I mean Gorilla**, O=orangutan.
and
Quote:
The second prediction - remnants of the 2p and 2q centromeres is documented in reference 4. The normal centromere found on human chromosome 2 lines up with the 2p chimp chromosome, and the remnants of the 2q chromosome is found at the expected location based upon the banding pattern.
and
Quote:
Telomeres in humans have been shown to consist of head to tail repeats of the bases 5'TTAGGG running toward the end of the chromosome. Furthermore, there is a characteristic pattern of the base pairs in what is called the pre-telomeric region, the region just before the telomere. When the vicinity of chromosome 2 where the fusion is expected to occur (based on comparison to chimp chromosomes 2p and 2q) is examined, we see first sequences that are characteristic of the pre-telomeric region, then a section of telomeric sequences, and then another section of pre-telomeric sequences. Furthermore, in the telomeric section, it is observed that there is a point where instead of being arranged head to tail, the telomeric repeats suddenly reverse direction - becoming (CCCTAA)3' instead of 5'(TTAGGG), and the second pre-telomeric section is also the reverse of the first telomeric section. This pattern is precisely as predicted by a telomere to telomere fusion of the chimpanzee (ancestor) 2p and 2q chromosomes, and in precisely the expected location.
I've never seen a creationist respond to this challenge. I've personally posted it on several forums in several discussions, and I've seen it posed by others many times too. Those of you who think evolution has no supporting evidence: what's your explanation, eh?