Animal form is the product of what two processes and how are these processes related?
development from an egg and evolution from ancestors
development is the process in which an egg eventually grows into adult form and evolution of form occurs through changes in development
Theory of punctuated equilibrium
Idea that evolution is marked by long periods of stasis and interrupted by brief intervals of rapid change
"Evo devo" is short for what?
What is the task of the "master" genes
control the formation and patterning of bodies and body parts
How did the discovery of developmental geneses change the way we think about animal relationships?
We can now see how different species formed and how they're related, even if they don't appear to be on the outside
Tool Kit Paradox
Paradox of great genetic similarity among diverse species
The development of a species depends on genes being turned on or off at certain times
where in the genome the "smoking guns" for evolution in form are found
First basic theme of animal design
related animals are made up of similar parts
Second basic theme of animal design
individual animals are made up of numbers of the same kinds of parts (like building blocks)
Modular architecture of animals
bodies are composed of similar, repeating parts
Bateson's contribution to our understanding of animal form
He noted that animals differ in the number and kind of repeating parts
Homologs (and examples)
Same structure modified in different ways in each species
ex. forelimbs of salamandars, mice, and our arms
Serial homologs and example
structures that arose as a repeated series and have become differentiated to varying degrees in different animals
ex. hindlimbs, our legs, hind legs of four-legged vertebrates (with respect to each other)
Symmetry of animal form
most species have an axis of symmetry. This gives us clues as to how the animal was built
Polarity of animal form
head to tail
top to bottom (back and front in humans)
near to far from the body
chemicals that cause monster-like mutations during embryonic development
Spemann's experiment with newt embryos. Significance of results?
He tied off a newt embryo first horizontal to the furrow and then perpendicular to it. It showed that the dorsal lip of the blastopore is critical for the organization of the embryo
Function of Spemann's "organizer"
It organizes the dorsal part of the embryo into neural structures and could initiate the development of another embryonic axis
Function of the Zone of Polarizing Activity (ZPA) in the chick limb
It creates a mirror image polarity in the digits of the chick wing
property of influencing the formation of pattern
some developmental variants in humans
extra ribs, extra nipples, extra fingers
extra body parts
What do homeotic mutants of fruit flies tell about developmental process?
A single gene can cause serial homologs
How does DNA connect all six kingdoms of organisms?
It's the basis of heredity for all 6 kingdoms
How are specialized cells within a single animal different from each other?
They make different proteins
Relationship between chromosomes and DNA
chromosomes are made up of DNA
In what way does DNA encode information?
sequence of base pairs. These sequences determine which proteins will be made
Transcription - RNA being made from DNA
Translation - RNA sequences code for proteins
How does the presence of lactose modify gene expression in E. coli?
When lactose is present, the usual gene repressor falls off the switch and turns the gene on to begin making the enzyme
Homeobox - 180 base-pair sequence in homeotic genes
Homeodomain - the corresponding protein domain it encodes
The homeodomain controls gene switches, so it affects the formation and identity of whole structures
Homeotic (Hox) genes
Homeotic genes with homeoboxes are Hox genes. They regulate development
Hox genes were originally studies in fruit flies. What other organisms have Hox genes?
almost all animals
What is the function of the Pax-6 gene in flies, mice, and humans?
Function of Dll gene in animals
Function of tinman gene
it's required in order to make the fly heart
How are the Pax-6, Dll, and tinman similar to each other?
They are all DNA-binding proteins. They all regulate on/off switches of genes
proteins that bind to DNA and directly turn gene transcription on or off
cells communicating via proteins
Kinds of genes in genetic tool kit
Hox proteins, Pax-6, tinman, Distal-less, cell-type regualtions, hedgehog, hormones, etc
What are the function of the hedgehog genes and how do they relate to polydactyly, cyclopia, fetal alcohol syndrome, and cancer in humans?
limb bud (ZPA)
polydactyly is caused by a mutation that affects sonci hedgehog expression during development.
Cyclopia is an inhibitor of sonic hedgehog signaling pathway. Alchol can have the same effect as this.
Mutations in the sonic hedgehog can cause tumors