Choose the evidence supporting the argument that a small number of changes in developmental regulatory genes can result in large phenotypic changes.(choose all that apply)

Question

_____  Closely related animals can have very different patterns of development.
_____  Most developmental genes are highly conserved.
_____  Much of phenotypic variation is environmentally caused.
_____  The developmental "toolkit" consists of a large number of genes.


Clarify Question
  · What is the key concept addressed by the question?
· What type of thinking is required?
· What key words does the question contain and what do they mean?
 
Gather Content
· What do you already know about developmental regulatory genes?
 
Consider Possibilities
· Consider the different answer options. Which can you rule out?
 
Choose Answer · Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
 
Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

__X__  Closely related animals can have very different patterns of development.
__X__  Most developmental genes are highly conserved.
_____  Much of phenotypic variation is environmentally caused.
_____  The developmental "toolkit" consists of a large number of genes.

Clarify Question
  · What is the key concept addressed by the question?
        o This question addresses developmental regulatory genes.
· What type of thinking is required?
        o This question is asking you to weigh and judge, or evaluate, evidence to choose the best of the possible answers.
· What key words does the question contain and what do they mean?
        o Developmental regulatory genes are simply genes that are known to regulate development.
        o Phenotypic changes are changes in the features of an organism.
 
Gather Content
· What do you already know about developmental regulatory genes?
        o Highly conserved developmental regulatory genes produce diverse morphologies.
        o A relatively small number of gene families, about two dozen, regulate animal and plant development.
        o Transcription factors and genes involved in signaling pathways are responsible for the coordination of development.
        o Even subtle changes in a signaling pathway can alter the enzyme that is activated or repressed, the transcription factor that is activated or repressed, or the activation or repression of gene expression. Any of these changes can have dramatic effects on the development of an organism.
 
Consider Possibilities
· Consider the different answer options. Which can you rule out?
        o Is the contention supported by the fact that much phenotypic variation is environmentally caused? No. It is not clear that that statement is correct – some variation is environmental, but some is genetic. Also that would not support the contention.
        o Is the contention supported by the fact that the developmental "toolkit" consists of a large number of genes? No. Again, that statement is not really correct. Many would argue that the huge variation in animal body plans is created by a surprisingly small developmental toolkit of the same genes used over and over.
 
Choose Answer · Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o Is the contention supported by the fact that closely related animals can have very different patterns of development? Yes. We learned about two closely-related species of sea urchins that have totally different modes of development, due to changes in the expression of developmental regulatory genes.
        o Is the contention supported by the fact that most developmental genes are highly conserved? Yes. The basic function of most developmental genes is maintained across the animal kingdom. But the deployment of the genes varies – their expression pattern in time, space, and levels.
 
Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o This question asked which statements support the idea that small changes in developmental regulatory genes can have large phenotypic effects.
        o The question required you to weigh and judge, or evaluate, evidence to choose the best of the possible answers.
        o Did you recognize that if closely related organisms have a big phenotypic difference, it is unlikely that a large number of mutations were acquired?
        o Did you recognize that developmental genes are well conserved – in other words, similar genes are found in distantly related species?
        o Did you appreciate that this means that the different looking organisms must be tinkering with the expression of the same basic “developmental toolkit”?