- Mar 3, 2006
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Contrary to what you might read from some IDIOT KWEATIOIST Website...
(Like ICR/Institute for Creation Research recently posted here.)
this is a SIMPLE one and a BIGGIE.
Easy to understand/SEE.
We have 23 pairs of Chromos, ALL GREAT Apes 24.
Their 2 a/b fused into our #2 as can be easily seen when put next to one another.
(Like ICR/Institute for Creation Research recently posted here.)
this is a SIMPLE one and a BIGGIE.
Easy to understand/SEE.
We have 23 pairs of Chromos, ALL GREAT Apes 24.
Their 2 a/b fused into our #2 as can be easily seen when put next to one another.
Introduction
All great apes apart from man have 24 pairs of chromosomes. There is therefore a hypothesis that the common ancestor of all great apes had 24 pairs of chromosomes and that the fusion of two of the ancestor's chromosomes created chromosome 2 in humans. The evidence for this hypothesis is very strong.
The Evidence
Evidence for fusing of two ancestral chromosomes to create human chromosome 2 and where there has been no fusion in other Great Apes is:
1) The analogous chromosomes (2p and 2q) in the non-human great apes can be shown, when laid end to end, to create an identical banding structure to the human chromosome 2. (1)
2) The remains of the sequence that the chromosome has on its ends (the telomere) is found in the middle of human chromosome 2 where the ancestral chromosomes fused. (2)
3) the detail of this region (pre-telomeric sequence, telomeric sequence, reversed telomeric sequence, pre-telomeric sequence) is exactly what we would expect from a fusion. (3)[/B]
4) this telomeric region is Exactly where one would expect to find it if a fusion had occurred in the middle of human chromosome 2.
5) the centromere of human chromosome 2 Lines up with the chimp chromosome 2p chromosomal centromere.
6) At the place where we would expect it on the human chromosome we find the Remnants of the chimp 2q centromere (4).
Not only is this Strong evidence for a fusion event, but it is also strong evidence for Common ancestry; in fact, it is hard to explain by any other mechanism.
Explanations
Telomere evidence
The telomere is a sequence of DNA at the end of the chromosome. The function of the telomere is to protect the ends of the chromosomal DNA strands during replication. The ends of the strands are very vulnerable to mutations or deletions. Telomeres consist of, or contain long stretches of simple DNA sequences that are repeated many times. The telomeres tend to be shortened over time and are restored by an enzyme called telomerase which lengthens the sequence. If the telomere becomes too short in somatic cells, errors in duplication can occur leading to cancers.
The telomere sequence is highly conserved in different groups of organisms. For example vertebrates have the sequence TTAGGG repeated many times. (In primates the sequence is repeated 500 to 3500 times). Adjacent to the telomere, are regions with other DNA repeats (known as Telomere Associated Repeats) but these regions, rather than being highly conserved, are highly polymorphic - that is they have many variations even within the same species. Nevertheless the pretelomeric region can be easily recognised in closely related species. Occasionally genes are found in the pretelomeric region.
Now these telomeric and pretelomeric sequences are normally found only on chromosome ends. However, in human chromosome 2, there is strong evidence for chromosome fusing in that there is a pretelomeric sequence, a telomeric sequence, an inverted telomeric sequence and an inverted pretelomeric sequence in that order in the middle of the chromosome.
Centromere evidence
Turning now to the centromere. The process of somatic cell division (mitosis) is as follows (this is a very brief and simplified summary to explain the centromere):
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Chromosome fusion
Demonstration that human chromosome 2 is the fusion of two ancestral chromosomes
www.evolutionpages.com
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