OK....I promised a tutorial.....comin' right up:
9. How exactly, could we use
the molecular structure of DNA to compare organisms for evolutionary relationships?
Well, the idea is to compare
the sequences of the nucleotide subunits: tiny differences in sequence mean closer relationship, larger differences, less close connections.
Makes sense?
a. And...the beauty of this kind of study is that
it uses quantitative measurement. Think how much easier this is than looking at two skulls and judging degrees of similarity.
It's a homerun.......right?
10. Not quite:
first of all, it is not easy to decide how to line up two different molecules of such immense length....I mean, at what point along the DNA do we consider similarities?
Secondly, it is not true that an alteration of one subunit in one place has a similar effect as an alteration in another.
Quick example of what changing a single nucleotide will do the genetic message:
a.
The nucleotides are 'read' in groups of three...Let's say that this short sentence is the information needed for the cell to build a protein:
"The sun was hot but the old man did not get his hat."
Simple, easily understood.....
b.
That sentence represents a gene, OK?..I know, much too short...but it's just an example!
Let's assume that each letter corresponds to a nucleotide base, and each word represents a
codon.
The definition of 'codon:' a unit that consists of three adjacent bases on a DNA molecule and that determines the position of a specific amino acid in a protein molecule during protein synthesis.
How do Cells Read Genes?
So...
.a mutation would leave out, or add, any one letter in the message, and then it is not the same message at all...
the 'mutation' makes the DNA meaningless at best....or lethal at worst!
Let me show you how: drop the first letter, and watch what that message becomes:
"hes unw ash otb utt heo ldm and idn otg eth ish at."
Now
apply the idea to the huge DNA molecule....and one can see that Darwin's premise, alterations in the DNA would produce a new species, doesn't do that at all.
Remember: the National Academy of Sciences says "The evidence for evolution from molecular biology is overwhelming and is growing quickly."
Hardly.
Who's zoomin' who?
Again your complete stupidity is showing!
They are talking about comparing the sequence of the base PAIRS.
Nucleotides are read in groups of 3 by messenger RNA, not DNA. The basic structure of the DNA molecule does not change, what changes is how the base PAIRS are ordered. That order is what contains the info for the cell and it is the order of the base PAIRS that can mutate, not the base PAIRS themselves or the basic structure of the DNA molecule itself.
Get it yet?
From RNA to Protein - Molecular Biology of the Cell - NCBI Bookshelf
An mRNA Sequence Is Decoded in Sets of Three Nucleotides
Once an
mRNA has been produced, by transcription and processing the information present in its
nucleotide sequence is used to synthesize a
protein. Transcription is simple to understand as a means of information transfer: since
DNA and
RNA are chemically and structurally similar, the DNA can act as a direct
template for the synthesis of RNA by
complementary base-pairing. As the term
transcription signifies, it is as if a message written out by hand is being converted, say, into a typewritten text. The language itself and the form of the message do not change, and the symbols used are closely related.
In contrast, the conversion of the information in
RNA into
protein represents a
translation of the information into another language that uses quite different symbols. Moreover, since there are only four different nucleotides in
mRNA and twenty different types of amino acids in a protein, this translation cannot be accounted for by a direct one-to-one correspondence between a
nucleotide in RNA and an
amino acid in protein. The nucleotide sequence of a
gene, through the medium of mRNA, is translated into the amino acid sequence of a protein by rules that are known as the
genetic code. This code was deciphered in the early 1960s.
The sequence of nucleotides in the
mRNA molecule is read consecutively in groups of three.
RNA is a linear
polymer of four different nucleotides, so there are 4 × 4 × 4 = 64 possible combinations of three nucleotides: the triplets AAA, AUA, AUG, and so on. However, only 20 different amino acids are commonly found in proteins. Either some
nucleotide triplets are never used, or the code is redundant and some amino acids are specified by more than one triplet. The second possibility is, in fact, the correct one, as shown by the completely deciphered
genetic code in
Figure 6-50. Each group of three consecutive nucleotides in RNA is called a
codon, and each
codon specifies either one
amino acid or a stop to the translation process.