Learning Journal- Week 8

	Three things that stood out	Type of knowledge	What makes these things stand out for you	Evidence/how you would test someone on this (select one “thing” only!)
1	Homeotic genes are genes that have the potential to mutate such that a segment develops/adopts the identity of a different segment	Conceptual	I found these fascinating! I didn’t previously know what a homeotic gene was, so to learn about the crazy world of hox clusters was really neat. I like thinking about all the pieces of our bodies that are classified under ‘homeotic’ genes, and it is strange to think about how much we take for granted its complicated regulation.	To test if someone knew what a homeotic gene is, I would likely ask them to identify whether a gene was homeotic based on a description of their WT and mutant phenotypes. For example, one should know a homeotic gene is a gene that can either be gain-of-function to look like the ‘next’ sequential segment, or loss-of-function to look like the ‘previous’ sequential segment. When given a WT phenotype, one should be able to compare a mutant and conceptually understand the patterns associated with mutations in homeotic genes. An example of this would be to look at a segment of your spine and realize that in the WT, each segment is different (T1,T2,T3, T4 etc) but in a mutant, one segment might look like its neighbor instead of itself (T1,T2,T2,T4 etc).
2	Another thing I’ve learned is how imprinting works. I learned that imprinting involves the ‘marking’ of a chromosome based on what sex the parent is. That is, the mother will produce eggs that have maternal imprinting and a father will produce sperm that have paternal imprinting. These maternally and paternally imprinted chromosomes will be passed on to their progeny. The tricky part is understanding how imprinting gets reset in the next generation. The progeny (let’s call it F1) will have one set of maternally imprinted chromosomes and one set of paternally imprinted chromosomes. When F1 creates gametes, the imprinting will be reset, such that if F1 is a female, she will produce eggs with the maternal imprint. These eggs will have the maternal imprint even if the chromosome it has was originally from the father in F0. The same is true for sperm but reverse—it will have a paternal imprint on its one set of chromosomes regardless of whether the chromosome was originally from the F0 father or mother.	Conceptual	I think a better question would be what person WOULDN’T find imprinting interesting. I hadn’t heard about imprinting before either, so to think that my genetics are not just based on what genes I inherited, but also who I got them from is really neat. I was reading an article the other day about how children tend to resemble their father more than their mother, regardless of which gender they were, and I found this interesting. Particularly so because most friends I have get along better to their fathers—and I wonder if there is some kind of evolutionary benefit to this.	I think the best way to test for this knowledge would be to have someone track imprinted genes throughout a phylogeny. Below this table I have drawn out a phylogeny showing the inheritance and imprinting trends of 2 genes. I know I have learned imprinting is because I am able to draw phylogenies like this and apply them to phenotypes in an individual. For instance, in the tree drawn below, I can identify the differential phenotypes in the F2 generations, and how both F2 females and F2 males who inherited chromosome2 from their mothers will gain the maternally imprinted C2, even though it was paternally imprinted in F1.
3	One of the things I feel I am starting to get a real handle on is how to create and describe a full model when given data. An example of this was shown in the midterm, but we do this every week with different problems. What I have learned (or rather, improved upon) is incorporating ALL the data given to me. I have learned how to be thorough in explaining how all data fits my model, and I have also learned what I need to include in order for the model to be complete.	Skills	Interpreting data from developmental-themed papers has always been a challenge for me, since most of my practical skills in paper-reading are actually in ecology (my thesis will be in microbial ecology). I think this course so far has helped me improve my skills as a developmental scientist by changing the way I look at data. In ecology, I find that data tends to emphasize trends, whereas developmental data stresses the importance of noting all details. (Of course, there are some exceptions to this, but in my experience this is what I’ve felt.) Thus, it was challenging for me to switch my perspective from an ecological to developmental and become comfortable (and confident) enough to begin forming models in my head.	I think the best way to test this skill would be to simply show a set of data and allow students to come up with models that incorporate all the information they can gather from it. To emphasize the idea that it is more important to create an ‘accurate’ model than a ‘correct’ one, I would probably also make the data fake– to encourage students to look at the problem without interference of previous knowledge about the system. (If I recall correctly, question 2 on the midterm was like this, and I really enjoyed that!).

 

Chromosome 1= C1                                                  Cx^m=maternally imprinted

Chromosome 2= C2                                                  Cx^p= paternally imprinted

Any other chromosome= Cx

 

 

 

F0.Female (C1, Cx)                F1.Female (C1^m,C2^p)

|Cross——->

F0.Male (C2, Cx)                    F1.male (C1^m,C2^p)

 

 

F1.Female (C1^m,C2^p)                         F2.Female (C1^m,Cx^p)

|Cross———->                                  F2.Female (C2^m,Cx^p)

F1.Male (Cx^m,Cx^p)                             F2.Male (C1^m,Cx^p)

.                                                            F2.Male (C2^m,Cx^p)

 

 

F1.Male (C1^m,C2^p)                             F2.Female (C1^p,Cx^m)

|Cross———->                                  F2.Female (C2^p,Cx^m)

F1.Female (Cx^m,Cx^p)                         F2.Male (C1^p,Cx^m)

.                                                            F2.Male (C2^p,Cx^m)