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dna???????????????????????????????
Last Updated on Tuesday, 20 July 2010 10:27 Written by Administrator Tuesday, 20 July 2010 10:27
Question by ?H.B.I.C.?: dna???????????????????????????????
How is DNA used to provide evidence that evolution has occurred?
A. The degree of similarities or differences in two organisms’ DNA sequences can provide clues about how long ago they diverged from a common ancestor.
B. All organisms have the same DNA sequence.
C. It isn’t. Scientists study protein sequences to learn about evolution.
D. The greater the number of differences in DNA sequence, the greater the likelihood that two organisms belong to the same species.
Best answer:
Answer by ?Melody?
A. The degree of similarities or differences in two organisms’ DNA sequences can provide clues about how long ago they diverged from a common ancestor.
- Organisms have different DNA sequences.
- Protein sequences are derived from codons in the DNA sequence (amino acids).
- The greater the number of differences in DNA sequence, the greater the likelihood that two organisms belong to DIFFERENT species
What do you think? Answer below!
A. Similarities in DNA structure can point to common ancestry, while the degree of change can indicate a general time of speciation.
a
D is stated backwards, C is incorrect, B is clearly wrong, so you are left with A, the most complete and correctly worded answer.
The answer is A.
Phylogenetic taxonomy (or cladistic taxonomy), organisms can be classified by clades, which are based on evolutionary grouping by ancestral traits. Ideally, classification should be based on homology; that is, shared characteristics that have been inherited from a common ancestor. The more recently two species have shared a common ancestor, the more homologies they share, and the more similar these homologies are.
Until recently, the study of homologies was limited to anatomical structures and pattern of embryonic development.
But now homologies can now also be studied at the level of
proteins, DNA-DNA Hybridization, Chromosome Painting and Comparing DNA Sequences.
A., since the rest are all wrong
The answer is A. First let’s go through the wrong answers so you can see how to eliminate them:
B – This statement is simply wrong. Besides, evolution deals with differentiation between species and variations in genetic material. The statement implies that you have the same genetic code as a bascterium, which is wrong.
C – Scientists can use proteins to get info, but that doesn’t answer the question. Also, this choice falsely claims that DNA isn’t examined.
D – This is also wrong. Organisms of the same species are more likely to have similar DNA. For example, your DNA is over 99% identical to my DNA, but I doubt that the same could be said while comparing your DNA to that of a mouse.
Now let’s go over the correct choice: Choice A says that similarities indicate how long ago species diverged. This is true. Over time, populations undergo small genetic mutations. After a certain amount of time, these mutations accumulate so that a new species is formed. Studies (and common sense) indicate that if two species differ by a few mutations, then they diverged recently. If the species have many mutations, they diverged long ago, giving them more time to seperate further.
a.