Your Inner Fish Chapter 3

Scientists have been wondering that what kind of cells in our body is responsible for making our body characteristics look different. The researchers started by observing chicken eggs and the embryos. They moved around tissues to see if different changes occur in the characteristics.

As a result, scientists discovered the mirror-image duplication. They removed a tissue to the other side of the limb of the chicken, and the fingers still grow normally. This explains that certain cells are capable of instructing others to form the structure of the body. This patch of tissue is called the zone of polarizing activity. (ZPA)

Later, scientists found that the gene capable of making body segment different from another is also present in fly. They named it hedgehog. Soon, it is uncovered that every limbed animal has the Sonic Hedgehog gene.

A scientists chose to do experiments on shark embryos since they are the first animals that have fins with skeletons. They are very distantly related to human beings. However, it is very difficult to obtain shark embryos; therefore, skates embryos are used instead. After experiments on such embryos, it is found that Sonic Hedgehog in these embryos were turned on and turned on in the patch of tissue at the back end of the fin, which matches the chicken and fly embryos. Through vitamin A treatment, the mirror-image fin is discovered in the embryos as well. Therefore, scientists found the gene that is responsible for making different segments in our limbs.

Survival of the Sickest Chapter 6

Our DNA is composed of about 3 billion nucleotides. All the genes in DNA are organized in 23 pairs of chromosomes: 50% from the father, 50% from the mother. The chromosomes contain information that code our body's characteristics. The dominant traits are always preferred in the case of one dominant trait and one recessive trait.

At first, scientists thought that only accidental mutations can cause genetic changes. For example, throughout the history, there were pandemics associated with the peaks of sunspot. The reason was that there was an antigenic shift/drift in our genes and it makes our bodies vulnerable to environment changes. Thus, we don't have the antibodies to fight with diseases. 

However, Barbara McClintock discovered that genetic changes can happen in a non-accidental way. McClintock observed genes in corns that sometimes the whole sequence of DNA moves from one place to another. And this phenomenon, she believed, is triggered by outside threats to the survival of the corn. Therefore, she called the genes in corns that make this change happen "jumping genes".

John Cairns also tested the mutation in genes by observing the genes of bacteria E. coli, which is a bacteria that digests the food. When Cairns fed nothing but lactose to the bacteria, the bacteria went through mutations that got rid of the lactose intolerance. He concluded that genes can choose to mutate. Other scientists propose the theory of "hypermutation", in which the genes are adapted to the environment due to massive increase in the mutation rate.

Originally, scientists found that only 3% of the genes in DNA are actually coding genes. They entitle the rest as "junk genes" at first. However, later they found that a large portion of noncoding genes are made of "jumping genes". Many strands of DNA contain viruses and bacteria that associated with human bodies a long time ago.

The Weissmann barrier distinguishes cells into germ cells and somatic cells. Changes in somatic cells can only happen in current carrier and cannot be passed on to the offspring.

Response to DNA

1.    Mendel designed the experiment between different types of peas. By breeding different types of peas together, Mendel compared the offspring of these peas and found that they have traits resembling to one of their two parents. As there are more crosses, both types of traits appear in undiluted form in the future offspring. This experiment shapes the perception of heritable variant from being blendable and ephemeral to long lasting and heritable.

2.     James Watson and Francis Crick discovered the double-helix structure of DNA.

3.     Mutations

·      Substitution of a single letter

·      Deletion of a block of letters

·      Duplication or insertion of new letters

·      Inversion and translocation of the letters present

4.     Evo-devo is the study of the effects of changes in important developmental genes and the role they play in evolution

5.     An individual that comes from a group that stops drinking milk after infancy is not able to tolerate lactose through adulthood, while the other group of people who drink milk through adulthood have lactase enzyme to digest lactose in milk.

Response to Founder Mutation

Response to Founder Mutations

According to Charles Darwin’s theory of evolution, all organisms can be traced to a common ancestor and nature selects the stronger ones to survive. However, nowadays millions of people are still struggling with diseases that are caused by gene mutations. If natural selection has taken place, why are there people with diseases still live and have offspring? The article “Founder Mutations” brings up several interesting points about this topic. First, the recessive genes are beneficial to the carriers in some cases. For example, sickle cell mutation arose repeated in regions in Africa and Middle East inflicted with malaria. A copy of sickle cell gene can help carriers survive malaria. Another example is that the patients of hemochromatosis have benefits as well. They can be protected from iron-deficiency anemia because the protein encoded in the gene helps the patients absorb iron more effectively. However, what is the origin of these gene mutations? In fact, the gene mutations come from a mutation founder. This founder passes this gene on to his offspring. Archaeological and geneticist’s evidence shows that certain diseases come from a specific area, confirming that human beings were able to migrate from places. In the video “The Journey of Man”, Spencer Wells visited the African tribe that was supposed to be oldest human tribe on the Earth. The tribesmen’s appearances are constituted with the characteristics from people all around the world. Wells also mentions the theory of migration started from Africa. Therefore, founder mutations can be found in numerous places around the world.

Brine Shirmp Lab Blog

Evolution—Brine Shrimp Lab

Question: In what environment can brine shrimp eggs be hatched more easily and quickly?

Hypothesis: Brine shrimps can be hatched in solutions with high concentration of salt.

Procedure

1.     Prepare 5 different solutions with 0%, 0.5%, 1.0%, 1.5%, and 2% of salt concentrations

2.     Put roughly 30 eggs on the plate and count the number of eggs under the microscope

3.     Put the plates into solutions

4.     Count the number of eggs and live shrimps after 24 hours

5.     Take out the live shrimps

6.     Count the number of eggs and live shrimps again after 48 hours

Observation:

In 0% solution, no eggs were hatched. The 0.5% solution has the highest hatching viability and the number goes down after 0.5% solution until 1.5% solution. The 2% solution has a hatching ability of 40%.

Conclusion

Therefore, it can be concluded that brine shrimps are able to adapt to any type of water environment with salt. This explains the instability of brine shrimp population at Utah. When the water evaporates, the salinity becomes higher in the water, and therefore the eggs were preserved in the water. When there is more rain, the concentration in water goes down and eggs can be hatched.

This experiment shows the organisms’ ability to adapt to the living environment and their methods to survive.

Hardy Weinberg Law Blog

Hardy-Weinberg Law

In the class, we learned the theory proposed by Hardy and Weinberg. The law is based on such conditions.

1.     The breeding population is large

2.     Mating is random

3.     There is no mutation of the alleles

4.     No differential migration occurs

5.     There is no selection.

There are two types of genes in the population. The organisms either have homozygous, heterozygous, and recessive genotypes.

P is the value of dominant allele frequency and q is the value of recessive allele frequency.

P+q=1 all the time

The value of p^2 indicates the possibility of homozygous genotypes in the population. The value of 2pq indicates the possibility of heterozygous genotypes in the population. The value of q^2 indicates the possibility of recessive genotypes.