DNA + Electrophoresis

By doing the DNA fingerprinting activity, I realized that the one whose blood was found on the scene is Suspect 4. When I was trying to figure out whose blood was found, I looked for the same pattern of the lines in the blood, trying to find an identical match. People's DNA patterns differ greatly because their parents carry a number of different genes, and alleles, that are completely different from anybody else on Earth. Hence, when their recessive and dominant alleles for traits combine, their offspring will inherit a completely unique genotype, or DNA sequence. If suspect four had an identical twin, my conclusions would be a little bit different. Identical twins come from the same zygote that gets split in half during pregnancy, meaning that their DNA would be the same. However, every person has different fingerprints. So, to come to a definite conclusion about whose blood was found on the crime scene, the forensic investigators would have to do a search for fingerprints, and see if they could find a pair that would match one of the identical twins. If no fingerprints were recovered, the detectives would just have to interrogate both of the twins, or send them for a lie-detector test, to figure out which one could have commited the crime. However, even if they did find who the blood belonged to, I do not believe that it would be enough evidence for the prosecutors to convict the client of a crime. Maybe, the suspect was just a by-stander who got hurt by the killer for witnessing the crime. On the other hand, the suspect could also have been just walking at the place the crime occured, not having the slight suspicion of what had happened. While walking, the suspect could have accidently hurt themselves by falling, slipping, etc. leaving their blood behind. So, in my opinion, the prosecution would need MUCH more evidence then a few blood samples.

Gel Electrophoresis:

A way that scientists can associate DNA from blood, saliva, etc. to a certain individual could be by using a method called electrophoresis. The electrophoresis basically helps scientists determine the guilty suspect by examining the length of their DNA strands. Electrophoresis functions in a fairly simple way. The samples of DNA are placed in tiny holes that are located within the gel, which acts as a filter for sorting the DNA. Once the DNA is placed, an electrical current is run through the gel, which makes the strands of DNA move across, from one end of the gel to another. Shorter strands will always move in front of, and faster then, the longer strands. Thus, after a period of time, the clumps of short and long strands will be seperated from each other, and grouped together. In this way, the DNA sorts itself. By staining the groups of DNA, they become visible to the naked eye. By comparing the different lengths of DNA strands and their groupings, the scientists can figure out whether the suspect is guilty. The online simulation is not that much different from the actual gel electrophoresis we did on our field-trip. The online simulation had a little bit more details, and I believe some parts of the process were better explained online than in the actual lab. Another difference is, obviously, that the actual real-life, lab application was much more difficult than the one online. It takes scientists a lot of practice to master the skill of handling the gel electrophoresis well, and being able to acquire helpful results for a certain case.

Dominance

Question: Is dominance always dominant?

By doing the online lab activity, I have realized that alleles are not always completely dominant. There are three types of dominance. The first type is dominance. That is when one allele is completely dominant over the other, and that is where Mendel's hypothesis's can be considered true. An example of dominance would be the color of pea plants. There are two colors, purple and white. The purple is the dominant, while the white is the recessive allele. If both are homozygous, and are crossed, all of the offspring will be purple. The next type of dominance is co-dominance. That means that both of the alleles of a certain trait are expressed equally. An example of this would be the human blood types. If the mother has blood type A, and the father has blood type B, the children will have blood type AB, meaning that the both of the alleles are expressed. Finally, the last type is incomplete dominance. This means that one allele for a specific trait is not completely dominant over the other. An example of this would the snapdragon flowers. If red and white flowers were bred together, the offspring would end up being pink, meaning that both of the alleles "mixed" together, to create a completely new color of snapdragon.

Gorilla Genome Analysis

It is believed that humans and gorillas last shared a common ancestor around ten million years ago. This hypothesis was made by sequencing and studying the whole gorilla genome, which was recently completed and analyzed. Gorilla are the last of all the great apes to have their DNA sequenced. The complete genome of humans, chimpanzees and orangutans has already been completed. The research that was led by scientists from Cambridge and Houston came to a number of very interesting conclusions. For example, it was discovered that 15% of the gorilla's genome is much closer, and much more similar, between us and the gorillas, in comparison to us and chimpanzees, which are believed to be our closest relative in the animal kingdom. However, it was also found out that humans and chimps share around 98% of the same genes, while humans and gorillas have 96% of the same DNA. The genomes of all three species have shown that the brain evolution is very accelerated in all of them, as well as that humans and gorillas have similar genes that characterize hearing and sensory perception. It was believed that the evolution of humans' hearing was related to the fact that many millions of years languages startes to emerge. However, this theory was disproven when scientists discovered that the gene that is associated with gorillas' hearing has been evolving at the same pace. The research has also shown that gorillas have very rough and hard knuckles because of a gene that creates protein, which makes the skin particularly harder. However, the main reason scientists wanted to find out gorillas' genome sequence is because they have the opportunity to learn more about evolution. Before, it was believed that the seperation of different ape species happened relatively quickly. However, now, it is believed that speciation happened over a longer period of time.
I think that it is really amazing that sceintists are not only stopping at sequencing our DNA, but also discovering the genomes of other animals. Further research could really tell us about how humans as a species evolved over time, and maybe, even, how we began. Sequencing more genomes from different species could broaden our knowledge and understanding, not only about how genes work, but also about our existence on Earth, which is quite extraordinary.



Link to Original Article: http://www.guardian.co.uk/science/2012/mar/07/gorilla-genome-analysis-new-human-link
Author: Alok Jha
Date: March 7th, 2012

Cytokinesis and Mitosis Reflection

In class, we did two virtual lab activities, that were supposed to broaden our knowledge od cell division, as well as nuclear division. From the first lab, there are quite a few things that I learned, but also a few things that surprised me. I learned all parts of the cellular devision cycle, and I was quite surprised that there are so many. The first part of the cell division is interphase. That is when the chromosomes, as well as the DNA, duplicate themselves within one cell. The next stage is the prophase. In the prophase, the chromosomes start becoming visible under the microscope, and they also begin moving. In the metaphase, the chromosomes all allign at the center of the nucleus, preparing for the next stage. Finally, in anaphase, the chromosomes move to the opposite poles of the cell. The last stage is telophase, when new membrane starts being created around the daughter nucleii, preparing for cell division. Even though there are so many stages of this cycle, most of the time the cell takes to duplicate is spent on the interphase (about 80-90%). In the second lab activity, I have learned to tell apart the nucleus of a dividing and non-dividing cells. I noticed that when the cell is not dividing, the nucleus is pure black, possibly being in interphase. However, in a dividing cell the chromosomes are visible on the onion tip root. The reason the tip of the onion root is used for these types of experiments is because the roots of plants are constantly growing, searching for nutrients in the soil. Thus, cell division is constantly taking place in those parts of the plant. What I really likes about the second lab was the fact that it allowed us as students to be scientists, and determine in what division stage the different cells are. Another thing that I found really interesting was the fact that there are some slight differences between the division of animal and plant cells. I did a little research, and found that there are two major differences between the cell division in animals and plants. Animal cells have centrioles, that help the chromosomes move to the opposite poles. Plants, on the other hand, do not have them. Another difference can be spotted during telephase. A plant cell creates a cell plate, which later turns into a cell wall. However, since animal cells do not have a cell wall, it doesn't create that cell plate.
Finally, there is one simple difference between mitosis and meiosis. During mitosis, the cell undergoes a simple division in two, where both of the daughter cells get exactly half of the original chromosomes created during interphase. However, meiosis is a cell division between sex cells. During this process, four daughter cells are created, since there are two nuclear divisions.

 

"Make the Right Call!" Lab

Guiding Question: How can you predict the results of genetic crosses?

Hypothesis:
I believe that the best way of prediction genetic crosses, and the inheritance of specific traits is through Punnett Squares. Punnett Squares combine the two different, either dominant or recessive alleles, of both of the parents, to see what the different genotypes of their offspring could be. However, I also do think that Punnett Squares are not always 100% accurate, hence the word "probability in genetics". Sometimes, the offspring may have a completely different genotype for a certain trait then you expected him/her to.

Data Collected:

Data Table 1:

Trial	Allele from Bag 1 (female)	Allele from Bag 2 (male)	Offspring’s alleles
1	B	b	Bb
2	B	b	Bb
3	B	b	Bb
4	B	b	Bb
5	B	b	Bb
6	B	b	Bb
7	B	b	Bb
8	B	b	Bb
9	B	b	Bb
10	B	b	Bb

Data Table 2:

Trial	Allele from Bag 1 (female)	Allele from Bag 2 (male)	Offspring’s alleles
1	B	B	BB
2	B	B	BB
3	B	B	BB
4	B	B	BB
5	B	b	Bb
6	B	B	BB
7	B	b	Bb
8	B	B	BB
9	B	B	BB
10	B	B	BB

Data Table 3:

Trial	Allele from Bag 1 (female)	Allele from Bag 2 (male)	Offspring’s alleles
1	B	b	Bb
2	b	b	bb
3	B	b	Bb
4	B	B	BB
5	B	B	BB
6	B	B	BB
7	b	B	Bb
8	b	b	bb
9	B	B	BB
10	B	b	Bb

Questions/Data Analysis:

1) Make a punnett square for each of the crosses you modeled in Part 1, Part 2 and Part 3.

                         

              

2) According to your results in Part 1, how many diffrent kinds of offspring are possible when the homozygous parents(BB and bb) are crossed? Do the results you obtained using the marble model agree with the results shown by a Punnett square?

According to the results, as well as the Punnett Square, if the parents are homozygous, meaning that both of their alleles are either dominant or recessive, their offpsring will show the dominant trait. However, since one of their parents carry a genotype for the recessive trait (bb), the children will be carriers of the recessive trait. Their genotype would be heterozygous, or Bb. The results that we obtained do show that all of the offspring would have the allele combination of Bb. In this case, the Punnett Square was 100% correct.

3) According to your results in Part 2, what percentage of offspring are likely to be homozygous when a homozygous parent (BB) and a heterozygous parent (Bb) are crossed? What percentage of offspring are likely to be heterozygous? Does the model agree with the results shown by a Punnett square?

When looking at the results that we gathered for Part 2 (the crossing of a heterozygous and homozygous parents), I can gather that they are not quite similar to the results that the Punnett Squares have shown. The Punnett Squares show that the probability of the offspring being heterozygous is 50%. However, in our results, only 20% of the overall picks ended up with both blue and white marbles.The other 50% on the Punnett Square were supposed to be homozygous, or BB. However, in our results showed that the majority of the outcome had the BB combination of alleles (80%). This shows that the more complex the genotype of the parents is, the less reliable the Punnett Square will be.

4) According to your results in Part 3, what diffrent kinds of offspring are possible when two heterozygous parents (BbxBb) are crossed? What percentage of each type of offspring are likely to be produced? Does the model agree with the results of a Punnett square?

When two heterozygous parents are crossed, there are three possible outcomes that could happen. According to the Punnett Squares, if two heterozygous parents are crossed, the outcome would be as follows: 25% of the offspring would have the genotype of BB, 25% would be bb, and finally, 50% of the offspring would inherit exactly the same alleles for a trait as their parents, which is Bb. However, again, the results that I got from the model are quite different from the ones shown in the Punnett Square. It turned out that 40% of the outcomes were Bb, 20% were bb, and the final 40% were BB.

5) For Part 3, if you did 100 trails instead of 10 trails, would your results be closer to the results shown in a punnett square? Explain.

I don't know whether the results would be closer to the ones shown by the Punnett Squares, but I do believe that the data gathered from 100 picks would be more reliable then the one where only 10 picks were made. If 100 picks were made, the data would probably be more accurate, and more statistics would be proved.

6) In a paragraph, explain how the marble model compares with a Punnett square. How are the two methods alike? How are they different?

The two methods are quite similar in a sense that both of them can be used to predict the probability of the offspring inherting certain traits from their parents. However, they do have a major difference. While the Punnett Square is mostly used for predicting what the possible outcome for the genotypes could be, the marble model is a sort of a test for the Punnett Square, showing how reliable the results from the Punnet Square can really be, when applying them to real-life situations.