Why Is Evo-Devo So Confusing?

[CookieSalesman]

I would appreciate some help explaining some things about evo-devo.
The way it's presented in class makes no sense at all.

I have desperately tried wikipedia but it just did NOT help in explaining anything.
Would appreciate some elucidation on my questions from the great physics forums...So to start:
1. De Baer's law, explaining why embryos are similar in early development.
Please tell me if I'm right.
My explanation is that changes to embryos are likely to become large fundamental changes that are deleterious. As a result embryonic development is strongly conserved. For instance, a small change in embryonic physical features can just end up resulting in outright death.
However these are some of my classmate's responses... Are they necessarily right or better?
-Animals resemble one another in early development- as they develop they look more and more different (Wait, is this even a reason? Am I missing something here)
And also, what does morphological similarity have to do with this...? There are a few answers under the sub-heading of morph. similarity, but I don't exactly understand what that has to do with this.

2. Please explain to me the difference between, and what are hox genes and what are homeotic genes?
I understand that hox genes are always homeotic genes...?
But... so homeotic genes are a special type of gene... but exactly how do they perform what they do? And why are they special? The thing is, I don't know what other types of genes there are, so there's nothing that I've been told saying that not all genes are homeotic, or what genes homeotic genes even affect. I feel I've been given a very bare framework of knowledge.
So... hox genes in: Yeast, animals...?

3. And what do transcription factors have to do with this? I know that they're proteins. I think they are produced by homeotic genes, and they bind to parts of DNA. Is that about it?

 

[Ygggdrasil]

1. De Baer's law, explaining why embryos are similar in early development.
Please tell me if I'm right.
My explanation is that changes to embryos are likely to become large fundamental changes that are deleterious. As a result embryonic development is strongly conserved. For instance, a small change in embryonic physical features can just end up resulting in outright death.

That seems like a decent answer. Think about changes in early embryonic development versus later embryonic development. Which are likely more likely to cause deleterious changes and which are more likely to cause changes with more limited effects.

2. Please explain to me the difference between, and what are hox genes and what are homeotic genes?
I understand that hox genes are always homeotic genes...?

That is correct.

But... so homeotic genes are a special type of gene... but exactly how do they perform what they do? And why are they special? The thing is, I don't know what other types of genes there are, so there's nothing that I've been told saying that not all genes are homeotic, or what genes homeotic genes even affect. I feel I've been given a very bare framework of knowledge.

Homeotic genes are defined by their function alone (regulating the development of anatomical structures), so identifying a gene as homeotic does not tell you about how it functions. For plenty of homeotic genes, we don't really understand in detail how they work.

3. And what do transcription factors have to do with this? I know that they're proteins. I think they are produced by homeotic genes, and they bind to parts of DNA. Is that about it?

Many homeotic genes encode transcription factors, but not all (I think...). There are also transcription factors that are not encoded by homeotic genes. Binding to DNA is an important property of transcription factors. What do transcription factors do when they bind to the DNA?

 

[CookieSalesman]

Thanks a lot!
That was helpful.

Transcription factors alter the magnitude or either turn on or off genes, I know that... But the mechanism for what they do after that is a bit complicated.

 

[Ygggdrasil]

Transcription factors alter the magnitude or either turn on or off genes, I know that... But the mechanism for what they do after that is a bit complicated.

Yup. Many biologists will just think of transcription factors as things that turn genes on or off without thinking about the mechanism of how they work. The exact mechanisms involved are indeed quite complicated and, especially in eukaryotic cells, not well understood in many cases.

 

[CookieSalesman]

Much appreciated.