CHAPTER 3:: HANDY GENES

Q.  Describe the hedgehog gene using animal examples.


- This chapter mainly concentrates on how the genome of all living organisms are similar to a great extent. Thus altering the genome of a particular species with a similar gene from another species can produce an entirely diffreent result. The author's lab can be divided into two different parts; the study of fossils and the study of DNA along with embryonic development. A number of chemicals secreted by our cells help develop our body. All of the genetic switches that control this occur between the third and eighth week after conception.

- Limb development is the core topic of this chapter. It was discovered in the 50's-60's that a certain patch of cells control limb development. If such a patch was to be removed, limb development would not occur. If it was turned over, limb devloment would occur backwards and if it was cut in half, there would be two limbs present instead of one (this was performed in chickens).

- In flies this gene was known as hedgehog, and in chickens it was known as sonic hedgehog. It was noticed that Vitamin A activates thesonic hedgehog. When this gene (extracted froma mouse) was injected into a shark, the limb development was affected in the same way as when the Vitamin A was injected. This meant that the protein and therefore the gene were effectively the same in a shark and a mouse. 

CHAPTER 1 :: FINDING YOUR INNER FISH

- In this chapter we are introduced to paleontology, the study of fossils. Today this field combined with geographical advancements have helped locate and identify fossils in a more systemized and efficient method. Paleontologiest use simple plans they also use modern technologies. These technologies include computers with programs that could scan places far from where a paleontologist is located. There are also radiographic devices that can see through some kinds of rock and allow them to visualize the bone inside.

- Shubin(the wuthor of this book) found fossils that over 350 million years old which provides teh evidence for the transition between fish and land-living animals. Ideally sedimentary rocks( such as limestone, sandstone, siltstone and shalesare) are thought to house fossils. However the type of rocks in which the fossil was found in helps  determine the characteristics of the organism the fossil belongs to. It also provides information about the organism's surrounding environment as well.

-  In the fall of 2004 paleontologists found what they thought was a intersect between a fish and a land living animal, which was later named “Tiktaalik. This fossil had bones which corresponded with the human arm and forearm, and even some parts of the wrist. This fish/human like fossil even had human like joints such as shoulders and elbows. Yet it also had fish like charecteristics

such as scales and fins with fin webbing.

 

- Neil Shubin thinks Taktaali explains something about our own bones as the entire shitf can be traced back to the loss of a few small bones in a fish like Tiktaalik. Tiktaalik is different in how it's connected and how it moves its body. The fish before Tiktaalik had its head connected to its body, so whenever the fish bent its body its head also bent. But Tiktaalik is completly free of the shoulders, the movement of amphibians, reptiles, birds and mammals (including us) can be traced to Tiktaalik.