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[BSCI 207] - Final Exam Guide - Ultimate 58 pages long Study Guide!


Department
Biological Sciences Program
Course Code
BSCI 207
Professor
Dr.Karen/ Dr.Hagg
Study Guide
Final

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UMD
BSCI 207
FINAL EXAM
STUDY GUIDE

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Phylogenetic Trees
Phylogenetic Trees (Common mistakes)
Morphological traits can’t be used to infer genetic relatedness.
Cannot be used to infer “primitive” organisms; more information is needed (fossils, etc.).
How is the tree of life (or a phylogenetic tree) determined?
Sequences are used
oDNA, RNA, amino acid sequences
oThese sequences are compared
More similarities = more recently two taxa had a common ancestor
oUses similarities between sequences
How do you decide which sequence to use?
oRate of change of sequences
Depends on when the groups diverged
Recently diverged = sequence that changes fast
From fastest changing to slowest changing:
Repetitive sequences mutate easily
oDNA polymerase “slips”
mtDNA > nuclear DNA
oMutates quickly due to the way it replicates
omtDNA is single stranded for a long time during replication
Introns > Exons
oIntrons are not highly selected, therefore mutates faster
than coding sections
3rd positions of codons > 1st or 2nd positions
o3rd position often does not affect protein sequence and
therefore mutates faster than 1st or 2nd positions
Highly constrained genes (sequences critical to organism function)
oStrongly selected for; mutates very slowly
More selection pressure = slower rate of mutation
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Less selection pressure = faster rate of mutation
Sequence changes too slow, not enough differences accumulate
Sequence changes too quickly, will become random and will not show
relationships
The three domains of life (bacteria, archaea, eukaryotes)
Prokaryotes
oMorphologies (form and structure) are very similar
Hard to determine phylogenetic relationships
oIn goes Woese, wants to:
Identify eukaryote ancestor
Understand prokaryote evolution
Determine ancestral gene families
oChose rRNA as sequence of choice
All organisms have it
Changes slowly
oResults:
Identified bacteria, archaea, and eukaryotes
But did not know which came first 
oTo solve this:
Need a common gene (that underwent a gene duplication event) that is
present in all three groups that also predates the divergence
Iwabe used two gene pairs to test
Results:
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