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EFB-311 Principles of Evolution Exam 4


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Transposable element
How does a transposon transpose itself?
A transposon codes for proteins that catalyze its own transposition.
What are the 3 Type I transposons?
RNA intermediate
Type II Transposon
Gene that migrates (transposes) and copies itself
Type I transposon; encodes reverse transcriptase, lacks LTRs, transcribed by RNA polymerase II
Long terminal repeat; type I transposon; contain LTRs ranging from 100bp-5kb in size, 8% of human genome
LINE (acronym)
Long interspersed nuclear elements
Short interspersed nuclear element; type I transposon; less than 500bp DNA segments that do not code for reverse transcriptase and rely on other mobile elements for transposition
Why are Type I transposons considered "RNA intermediate" and Type IIs are considered "DNA?"
Type I transposons have an RNA intermediate form-- they copy and paste themselves. Type II transposons have no intermediate and rely on the transposase enzyme to copy and paste their sequences.
What are 2 hypotheses for the existence of transposons?
  • 1. They benefit the organism (they introduce antibiotics through plasmids from Type IIs, and generate non-forward-looking variation.
  • 2. They replicate selfishly (at gene level, not organism level).
The selfish replication and genetic parasitism of a transposon can be counteracted by what?
Natural selection on the afflicted individual
Is the genome a cohesive unit? Why or why not?
No. The genome consists of a collection of mostly cooperating, sometimes warring genes.
Genes moving between organisms, esp. in bacteria
What are 3 forms of lateral gene transfer in bacteria?
  • TRANSDUCTION (phage picks up and moves host DNA)
  • TRANSFORMATION (bacteria picks up DNA from the environment)
  • CONJUGATION (bacteria sex with plasmids)
Circular genetic element that codes for antibiotic resistance, virulence factors and metabolic enzymes
Genes and gene groups can have different evolutionary interests from the ______.
Organism which lives in the body/cells of another organism
Can a host acquire genes from its endosymbiont?
Yes, freq
Master switches for regulatory cascades are ____ _____.
highly conserved
What are 3 ways a developmental plan can be modified?
Location, timing and amount of development
Where does evolution work on a gene sequence?
Promoter region
If all cells have the same genes, how do cells know where they are?
Position in space and time relative to others determines function
Bodies are developed by the interactions of a ______ ___ ____ ____.
network of regulatory genes
Cell fate is determined by position, time and concentration of signals
Group of genes that specify the anterior-posterior axis and segment identity during development
How does evolution produce tremendous diversity from highly conserved patterning genes?
Tweaking, co-opting and copying
Hox genes occur in ____ of __ to ___.
clusters, 5 to 10
Fewer Hox genes are produced ___ in development when the ___ is formed, and more ___ in development when the ____ is formed.
late, posterior, early, anterior
Hox genes arose after the division between plants and animals.
Portion of a gene sequence that interacts with DNA transcriptional regulator; location of Hox genes
There were __ ancestral Hox genes that duplicated in the ____ ______ to produce __ to __ Hox genes in Bilaterata.
5, Cambrian Explosion, 8 to 10
The __ to __ Bilaterata Hox genes duplicated to form the Hox genes of __, which duplicated again to form the Hox genes of ___ _____ ____.
8 to 10, vertebrata, ray finned fishes
We have 9 Hox genes in common with what group of organisms?
Ectodermal structure overlying embryonic limb bud, becomes skin of limb; formation initiated by secretion of FGF-10, then the AER secretes FGF-8 and FGF-4 to stimulate limb development
Segment of mesenchyme signaled by the AER which in-turn signals a limb bud to form an anterior-posterior axis
Hox genes are co-opted by the ____ __ ____ ___ to set up limb segments.
zone of polarizing activity
Morphogen required by the ZPA for anterior-posterior patterning; can be transplanted to produce mirror image digit duplications
Smallest evolutionarily independent unit
What are the 3 concepts of "species?"
Morphospecies, biospecies and phylogenetic species
Species based on monophyly

Widely applicable to living, extinct, sexual and asexual species, and can ID cryptic species

Does not work well with fossils, requires well-supported phylogeny and time, not sure how much divergence is needed to count

What are the 3 steps of species formation? When does each occur?
  • 1. Populations become genetically isolated
  • 2. Traits and allele frequencies diverge from ancestral population
  • 3. Secondary contact reinforces divergence via reproductive isolation
Steps 1 and 2 can happen together, Step 3 may never happen.
Geographically isolated population
Allopatry where one population wanders and becomes isolated, ex. mainland species coming across a volcano-born island
Allopatry where an existing population is divided, ex. mainland populations separated onto islands by rising seas
Loss of genetic variation when a small number of individuals from a large population found a new population; effect of genetic drift (variation due to chance) increases greatly
Speciation occurring in a continuously distributed population; gene gradient tends to reflect environmental gradient
Speciation occurring within the ancestral population range via strong assortive mating (ex. sexual selection)
What happens when hybrids between new and ancestral pops are less fit than parents?
Selection for reduction of interbreeding
What happens when hybrids between new and ancestral pops are equally fit compared to their parents?
Homogenization of two parent pops
What happens when hybrids between new and ancestral populations are more fit than their parents?
Third species forms OR an ecotone
Who determined the different groups of old world monkeys, apes and humans? How, and in what year?
Thomas Huxley, anatomy, 1863
Who determined the groups of apes, chimps, humans monkeys? How? In what year?
Sarich and Wilson, cross-reactivity of serum albumin, 1967
Most genetic evidence suggests humans are more closely related to ___ than ___.
chimps, gorillas
How long ago did chimps and humans diverge from gorillas?
6.4 mya
How long ago did humans diverge from chimps?
5 mya
Some genes suggest humans are more closely related to gorillas than chimps.
How different is human mtDNA from chimp mtDNA? amino acids? non-coding DNA? in/dels?
  • 10% difference in mtDNA
  • 1.34% difference in amino acids
  • 1.24-1.64% (35M SNPs) difference in non-coding DNA
  • 5M difference in in/dels
Who determined the Earth was 74,000 years old?
Who determined the Earth was less than 40M years old? In what year?
Lord Kelvin, 1897
How was the current accepted age of the Earth determined? What is it?
Radiometric dating, 4.5 billion years
How old is the oldest terrestrial rock?
3.8 billion years
How old are the oldest bacteria-like microfossils? Where were they found?
3.26 billion years, South Africa
Why did Earth have no life in the first 0.5 billion years of its existence?
Constantly bombarded by meteors
How old are the controversial "worms" discovered by Bill Schopf?
3.45 billion years
What are 3 characteristics of a universal ancestral gene?
  • 1. Present in all extant organisms
  • 2. Has a function
  • 3. Strong stabilizing selection
Who used analysis of a small subunit of ribosomal RNA to determine the division of organisms into the modern clades?
Carl Woese
Last universal common ancestor (2 bya); enzymes made from protein, capacity to make protein, 30 universal genes as ribosomal proteins, 15 aminoacyl-tRNAs (attach amino acids to tRNAs)
What are 2 hypotheses about the identity of LUCA?
  • 1. LUCA is a community with lateral gene transfer.
  • 2. LUCA was a virus.
Large virus that looks like a bacterium

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