genes and development

Omne vivum ex ovo

“all life from the egg”

All multicellular organisms develop from a single cell, the fertilised egg = zygote

how diversity in cell types occurs

During embryogenesis:

• The organism gets bigger (proliferation)

• The organism gets more complex (differentiation)

Regulation and programming

• Cells will eventually differentiate to adopt a specific fate and function

• this needs to be coordinated, often through cell-cell signalling

profileration

increase in cell number resulting in cell growth

differentiation

cells become different from each other

All cells in an organism contain the same

genetic information (the same genes)

for cell to become different

they must be equipped with different proteins

➢Protein are encoded by genes

➢So, to become different, cells must express different genes

Genetic information is stored in

DNA as genes to make proteins

first step to synthesise protein

copy of mRNA made during transcription

second step of protein synthesis

translation

How do we know where a gene is active?

In situ hybridisation - a staining method that reveals all cells in which a certain gene is active

Each gene has a specific ‘expression pattern’ of stained cells in the embryo

Blue colour indicates the cells which express the gene, and where the corresponding protein is likely to act

how situ hybridisation works

binding to the mRNA in genes that are being expressed

FGF10 is required for

limb development

Pax6

regulator of eye development

pax6 mutation in humans leads to

aniridia (absence of iris).

overexpression of pax6

induces eye markers

leads to formation of extra eyes

loss of pax6 in xenopus

has varying effects

which include smaller eyes or loss of eye or loss of iris

aniridia

loss of pigment/iris

due to mutation in pax6