MOLECULAR EVOLUTION LESSONS
on ENSIweb
Tutorial: Investigating Evolutionary Questions
Using Online Molecular Databases: SYNOPSIS Students are
guided through a process in which three questions are addressed
by retrieving beta hemoglobin sequences from online databases,
and using online tools to compare those sequences in student-selected
animals. The questions: (1) Are bats birds, or mammals?; (2)
Are whales more closely related to artiodactyls, or perissodactyls?;
and (3) should birds be included in the class Reptilia?
PRINCIPAL CONCEPT: Degrees of biological relationship can be
inferred from comparisons of selected molecules.
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Molecular
Sequences & Primate Evolution (beta Hemoglobin):
SYNOPSIS: Students compare differences in amino acids in the
beta hemoglobin from representative primates, complete a matrix
of those differences, and from these data, construct and interpret
cladograms as they reflect relationships and timing of divergence.
PRINCIPAL CONCEPT: Modern apes and humans evolved from a common
ancestor.
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Molecular
Biology & Phylogeny (cytochrome c):
SYNOPSIS: Amino acid sequences in cytochrome-c are compared for
several different animals, and the number of differences found
are used to infer degrees of relationship. These data are also
compared with a cladogram constructed for those same animals
from their anatomical features, providing an example of independent
confirmation.
PRINCIPAL CONCEPT: Independent confirmation strengthens scientific
inferences.
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Chromosome Fusion:
SYNOPSIS: The banding pattern of our long chromosome #2 closely
matches the banding patterns of two shorter chromosomes found
in apes. This suggests the likelihood that our #2 chromosome
was formed by the head-to-head fusion (merging) of those two
shorter chromosomes in an early human ancestor. To test that
hypothesis, students search for evidence of this fusion in the
DNA of chromosome #2, using online databases (or printouts of
same) to seek the sequences typical of terminal DNA (telomeres).
In the process, students see how patterns can reveal events of
the past, thereby merging elements of both experimental and historical
science. They discover the huge amount of DNA in a chromosome,
get a sense of gene size and the number of pseudogenes, correlate
visible chromosome bands and their contained DNA, and learn to
use an accessible resource for further study and inquiry. Try
the easier-to-teach variation: Mystery of the Matching Marks (Telomeres).
Uses PowerPoint with short DNA search for the tell-tale telomers
in our #2 chromosome to test the hypothesis that we share a common
ancestor with the chimpanzees..
PRINCIPAL CONCEPT: Modern apes and humans evolved from a common
ancestor.
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Whale
Ankles and DNA: Testing hypothesis that the closest
living relative of whales is the hippo.
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Pseudogene Suite (3 lessons: A,B,C): Vitamin C and Common Ancestry: SYNOPSIS: Students compare the DNA sequence data for a portion of the rat GULO gene (which helps make vitamin C) to the corresponding sequence in the inactive human GULO gene by translating the sequences and by aligning them. This lays ground work for exploring pseudogenes and the significance of these DNA sequences in recognizing shared common ancestry vs the notion of "intelligent design" (Lesson B). Lesson C is a tutorial which introduces students to the online tools for analyzing DNA sequences. PRINCIPAL CONCEPT: Mutation may create an inactive version of a gene (an inactive allele), and, over generations, the active gene (allele) may be lost from the species, leaving only the inactive gene (pseudogene).
Click
HERE for excellent article on Moledular Clues to Evolution
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