Modularity

Question 1

biological Modularity

Answer 1

organization of biological systems into discrete, interconnected units that have strong internal connections but limited connections with other modules. Modularity scales across biology from the genome to ecosystems

Modularity is a way to break down pleiotropy

it is the phenomenon of quasi-independent units within the organism (genome and phenomena)

a result of the balance between parcellation and integration

high degreed of modularity are often associated with high degrees of phenotypic variation and species diversity

Question 2

metamerism

Answer 2

unspecialized segments

Question 3

tagmosis

Answer 3

specialized segments ,
segmentation + specialized appendages = tagmosis

Question 4

segmental complexity/segment specialization

Answer 4

There is an overall trend from unorganized to organized body segments, so moving from an un-modular animal to a highly modular one.
This is what creates potential for a lot of diversity.
One of the reasons is that any given segment can be modified without necessarily affecting other segments.
(counters high pleiotropy!)

Question 5

parcellation and integration

Answer 5

parcellation = separation of genes and their functions
Integration = mixing of genes and their functions

a way to acheive modularity

Question 6

modularity in the GRNs

Answer 6

Kernels are usually conserved across evolutionary variation, which implies functional modularity of the genome.

those fundamentals that make up body plans seem to have reached a “sweet spot”

Parts of the GRN have taxonomic associations; therefore, early kernels are associated with phyla and even superphyla.

Question 7

homeotic mutations

Answer 7

can be considered as mismatched GRN kernels switched on in the wrong place

for example: fly with legs instead of antennas on its head

Question 8

modularities behavior

Answer 8

Modules can expand and contract.

For example, snakes lose most vertebral modularity and Hox regionalization. (contraction)

In chick and mouse somites, the genes are moving up and down the axial column and making different modules as they go (expansion)

Question 9

Hox-6 expression in vertebrates with different neck lengths

Answer 9

Hox-6 expression determines the “starting point” of the neck.
It poses a high developmental constraint.

There are 7 cervical vertebrae in nearly all mammals

people with more or less have nearly 100% probability of juvenile cancer (RIP)

Question 10

pleiotropy

Answer 10

mutations in most genes affect more than one trait

The Hox code is VERY pleiotropic!
Hox A and D are expressed in numerous regions within the developping embryo and adult

Pleiotropy can be “combatted” with modularity

Question 11

what is the link between modularity and diversity

Answer 11

High degrees of modularity are often associated with high degrees of phenotypic variation and species diversity.
partially because modularity allows for modules to evolve and variate without impacting other modules, they can evolve separately, bypassing pleiotropy