The Inner Fish Chapter 3

Scientists attempt to discover the type of cells responsible for making each of our body characteristics appear different. By purposefully tampering with an embryo's development scientists hope that they can gain insight on the nature of genes by looking at the resulting mutation. Obviously, human embryos were out of the question, so scientists decided to use chicken.

Randy Dahn decided to use sharks for his experiment because shark were the first animals with skeletons and also having a fin. In their embryonic stage, they also show striking similarity to a humans'. Due to the difficulty of obtaining shark embryos (possibly due to animal activists), skates embryos are used instead. The hedgehog gene in these embryos were found in a patch of tissue in the back end of the animal's fin, and mirror image duplication also occurred when Dahn treated the embryos with vitamin A.

Scientists have discovered and confirmed the existence of these hedgehog genes which are responsible for making our body look the way it is, and create limbs.

Survival Of the Sickest Chapter 6

Every human being starts of as 1 single cell, and it contains every single genetic instruction to construct that human being. These instructions are in 3 billion pairs of nucleotides (DNA base pairs),there are also around 30000 genes, organized in 23 pairs of chromosomes for a total of forty six. One set of chromosomes will come from the mother, and another set from the father.Chromosomes contain information that determines us as a person. As for traits, the dominant traits are always more influential than recessive.

Scientists first discovered that only 3 percent of our DNA contains instructions for building cells, and decided to call the rest as junk DNA, DNA which doesn't help nor hinder our lives. However, later studies have discovered that these DNA are actually traces of past viruses or bacteria that have been in our body. They are now called non-coding DNA.

For a long time scientists also believed that genetic mutations which occurred in ones genes were only from accidents. Such as exposure to radiation or sunspots. However, Barbara McClintock discovered otherwise, she found jumping genes in corn and discovered that their whole sequence of DNA moves from one place to another, and has erratic behavior.This also explained why scientists thought that there were once more than 100000 genes in a human body, one for each specific job/trait, now it is only estimated to be around 30000, since McClintock discovered that through the shuffling of these genes, they can do a huge amount of different things.

Scientists also conclude that genes can adapt to its environment. John Cairns once fed only lactose to a E. Coli bacteria (a food digesting bacteria), and discovered that the bacteria underwent mutations to become lactose tolerant.This shows that genes can determine and choose whether or not they want to mutate.

The best example of these shifting and jumping genes would be the human immune system. Why is it that after contracting chicken pox for the first time, it is near impossible to get it another time in your life? This is because the human body has genes which create antibodies to fight foreign invaders such as viruses and bacteria, and genes adapts to fight against new types of viruses by creating different antibodies.

From Atoms To Traits

1. Mendel conducted an experiment with many different types of peas. He cross-bred these different species of peas with each other and discovered that their offspring would have traits resembling one of their parents. As more peas are cross-bred, more traits of different peas appeared significantly in future offspring. The pea experiment by Mendal divided heritable traits into 2 categories, one being blendable and ephemeral and the other heritable and lasting for a long period of time.
    2. The structure of the DNA was discovered by James Watson and Francis Crick. It is in the shape of a double-helix

3. Variations causing mutation can be caused by: a single letter replaced in the DNA strand, a string of letters gone, duplication or addition of new letters, and transformation of the originial letters.

4. Evo-devo: The study of the effects of mutation in developing genes and its role in the process of evolution.

5. A child born from parents that does not drink milk after their infancy does not have the lactase enzyme to digest milk through adulthood, therefore they are lactose intolerant. However, a child from a family that does drink milk after infancy will be lactose tolerant.

Origin of Man: The Out-Of-Africa Theory

Over twenty years ago, studies made by geneticists hinted at an incredible and unbelievable explanation for the origin of man kind. By tracing the trails of DNA left behind in multiple regions in the world, gathering samples from various different races and isolated indigenous tribes, scientists came up with a theory that all races of humans we know today originated from one location in mid-south Africa. Only after extensive research, and numerous DNA samples, have scientists been able to confidently publish their new founding. This new theory, as irrational as it sounds, after numerous experiments conducted was found to be more plausible and reasonable than the old theory of many different species of homosapiens in different areas and interbreeding.

Gathering such extensive data was difficult. It is an arduous task to travel to remote regions of earth and meet with indigenous tribes that have little to none outside contact. Many tribes even refused to cooperate, as they were suspicious with why scientists were drawing blood samples from and gathering DNA samples from their saliva with a cotton swab.

The long standing opposing theory to the “out-of-Africa” theory is called the Multiregional theory. To this day, many scientists still believe that homosapiens developed in different regions, adapted to their surroundings, and interbreed to preserve their race and create many different features of early humans. People argued that a large percent of the population is a result of this interbreeding, not from a single stemmed African species. The debate continues onwards, however, more and more genealogical evidence has been discovered to support the out-of Africa theory.

Perhaps the one obstacle that has troubled scientists most is the lack of physical evidence. A DNA trail clearly shows that traces of DNA and microorganisms were left behind during the migration out of Africa. However, there hasn’t been any fossils/prehistoric tools found on these trails, leading many scientists to question the validity of this theory. However, fossils are usually incredibly difficult to find, and many scientists argue that fossils or physical evidence is inapplicable in this particular research.

New Topic: Evolution & Fossils

Today in class we have started a new topic on evolution. I have always believed evolution and anything to do with fossils are a part of paleontology; apparently, I was wrong as we focused a lot on how genes and DNA affects on organism's adaptations and development over time.

Formation Of A Fossil:

1. Organism dies, bones must remain
2. Bones buried within sedimentary rocks
3. Bones/shells are preserved,sometimes through crystallization
4. After movement of rocks over a long period of time,old fossils are buried deeper whilst newer ones from above
5. Fossils can be discovered through weathering, erosion and other natural means.
Or just paleontologists digging.

Oldest rocks at bottom, newest at top

The Theory of Evolution

With the discovery of fossils Charles Darwin formulated a theory of evolution.
Before class, we watched a video describing the definition of a theory. A theory is formed
by a hypothesis, observation, evidence, and conclusion. Homology is a term used to describe
the similar structures of different organisms in order to determine any common ancestries.
Organisms mutate through millions of years in order to adapt to the ever-changing living
environments. When the structure of 2 different animals show qualities of similarity, they
are called analogous structures. An example could be the dragonfly and a bird, which both have wings but possess vastly different skeletons.

                                    

We also learned about how to prove the theory of evolution. We learned and read about the Tiktaalik,
a fish that was also amphibian. The Tiktaalik served as a missling link between the transition
of sea-living organisms to land-dwellers. It shared common characteristics of fish and early
amphibians. For example, it had a limbs that resembled a fish's fin, however they allowed
the titaalik to swim in shallow water and also move on land. Soon becoming an amphibian.

                                       

                                                                  The Titaalik
                           

We also did an activity in class where we analyzed the biomedical evidence of different organisms,
such as DNA and protein. Finally we have reached the biology part of evolution. By comparing a
chemical named cytochrome C in different organisms, we can construct a detailed graph and cladogram
to determine which organisms are closely related to each other. The less differences, the more similar
2 organisms are, and thereby proving that the 2 organisms have a common ancestor.

                             

                                 We spent a long time compiling a list like this, determining the differences

                                 between strands of cytochrome c from different animals.