104 Evo-Devo

What does the "Sonic Hedgehog" gene do?

• Repeat spine vertebrae

• directs limb development

• Turns off genes

• Causes mutations

A conserved DNA sequence that allows us to recognize a homeotic gene (which regulate development in animals);

• homeotic gene

• homeobox

• transcription factor

• euchromatin

a gene that controls the development of a specific adult structure

• homeotic gene

• structural gene

• regulator gene

• proto-oncogene

What is the first step in limb development in a vertebrate?

• The Sonic Hedgehog gene turns on and produces the Sonic Hedgehog protein

• The limb bud starts to grow.

• The fingers grow first and then behind the fingers, the hand, wrist and arm bones grow in reverse order.

• The bones grow in order: humerus first, then radius and ulna, then wrist, then the bones of the palm and finally the fingers.

What does the Sonic Hedgehog protein do?

• The Sonic Hedgehog protein turns on the growth of the bones of the limb.

• The Sonic Hedgehog protein turns on the Sonic Hedgehog gene.

• The Sonic Hedgehog protein is only important when it mutates because it could mean that for example, horns may grow from the wrong part of the body.

Which group of genes is responsible for directing the animal develoment?

• Gap Genes

• Homeotic Genes - Hox Genes are one example of homeotic genes

• Sonic Hedgehog proteins

• ZPA genes

Which group of homeotic genes directs the development of body segments in animals?

• Hox genes

• Gap-genes

• ZPA-genes

• Sonic Hedgehog protein

The hox gene, Sonic Hedgehog, directs limb development in the embryo. If Sonic Hedgehog was turned on in the wrong place, lets say at the back of the body, what would happen?

• Nothing. Sonic Hedgehog only works if it is turned on in the correct place.

• A limb would start to grow where Sonic Hedgehog was turned on in the back of the developing embryo.

• The embryo would grow two limbs in place where usually only one limb goes.

• The embryo would grow horns even thought the species usually does not have horns.

Mice have eyes similar to our eyes. Insect eyes are very different from our type of eye. What happens when the ZPA for eye development is moved from a fly embryo to a mouse embryo?

• The mouse will develop with insect eyes.

• The fly will develop with mouse eyes.

• The mouse embryo uses the instructions from the fly ZPA to build a perfectly nice mouse eye.

• The mouse embryo develops eyes that are somewhat normal and somewhat like fly eyes.

Mice have eyes similar to our eyes. Insect eyes are very different from our type of eye. When the ZPA for eye development is moved from a fly embryo to a mouse embryo, the mouse develops normal eyes just fine. Why?

• The mouse embryo has back-up genes, so it can ignore the fly ZPA.

• The mouse embryo uses the fly ZPA like a tool to build its own eyes.

• This actually doesn't work. The mouse embryo would be blind.

• The mouse actually develops fly eyes with the information from the fly ZPA.