Question

Hox Genes- EVO DEVO

Development is often modular. For example, head traits like width and height often change in concert, and independently of traits in other parts of the body such as femur length.

A) Why might this make sense given what you know about Hox genes?

B) Would you expect more or less constraint on the evolution of development as the number of Hox genes increases? Why?

Answer 1

(A)

Hox genes also known as homeobox genes are group of genes which are present in clustures . There genes encodes transcription factor & control the expression of those genes which axis regulate the formation of body structures along the anterior posterior axis during the early development of embryo.

Hox genes contain Homeodomain which is 180 base pairs DNA sequence act as transcription factor by binding to the DNA & control the expression of other genes fate.

Mutation in the Hox genes leads to the abnormal formation of structures for eg. if there is a mutation in the antennaepaedia hox genes of drosophilla legs arises from the head region of drosophilla instead of antenna.

Hox genes are present in all animals and conserved during the evolution.

(B)

There is a variation in the number and arrangement of hox genes among the different animals. As the number of hox genes increases there is also increase in the complexity of body structure of animals. for eg. in drosophila there is a two hox gene cluster situated on the same chromosome and in human there are four hox gene cluster situated on different chromosomes. which complexes the body structure of human .so we expect less constraint on the evolution of development as the number of hox gene increases.