Double-stranded DNA free ends

                    This article discuss about problems with free DNA ends in eukaryotic cells. Free reactive DNA ends are caused by double-strand DNA breaks (DSB) which results in the development of various mechanisms to ensure that free DNA ends are non-reactive. DSB is a chemically modified process and is considered very toxemic to the cell and genetic materials. It can generate free ends DNA that has to be repaired. Free end DNA can be very dangerous to the eukaryotic organism. Recombination-base mechanism is a mechanism that generates region of homology pairs during meiosis and mitosis. This may result in translocation and deletion of DNA and could lead genome instability when DNA fails to repair itself, or several x-linked disease such as the Turner's syndrome that is related to the non-allelic homologous combination and random arrangement of the X-chromosome from female. Free end DNA relates to x-linked diseases because DNA is engaged in the homologous recombinant with X chromosome in female during meiosis. This provides more possibility for mispairing recombination.

http://www.hindawi.com/isrn/molecular.biology/2012/345805/fig1/ (image: Structure of DSB)

http://atlasgeneticsoncology.org/Deep/Images/DoubleStrandBreak4.jpg 

                    The double-stand DNA breaks (DSB) occur during the process of DNA replication when the phosphodiester backbone of both strands of the same DNA helix is broken and is separated. Though DSB may lead to genetic diseases because it is the cause of alteration of the DNA structure and generate free DNA ends, its occurrence is required throughout the cell cycle. Free DNA ends are "unprotected DNA" that should remain inactive. If the fragment is reactive, it will intact with other DNA ends. This is call the genomic fusion, which could lead to genomic instability from the breakdown of one eukaryotic chromosome to long term effects such as inherited diseases or somatic origin diseases such as cancer or syndromes. The risk for genomic instability, thus, can be trigger from recombinant mechanisms. Therefore it is difficult to cease the unprotected DNA from activating or keep free-ends non-reactive because scientists cannot control the repairing process of DNA free end and the presence of DSB is required in the cell cycle.

http://www.genome.jp/kegg/pathway/ko/ko03450.png

                    The article also talks about factors that may increase or lower the rate of occurrence of DSB. Ionizing radiation and radiomimetic chemicals such short-wavelength UV are chemical factors that increase the rate of occurrence of DSB. Meiotic and mitotic recombination is the only mechanisms that can generate genetic diversity and requires DSB. Recombination of non-sister chromatids in prophase I of meiosis create a largest variability of unique allelic combination. Both chromosomes in meiosis are allelic homologous despite the DNA sequence. Non-allelic homologous combination (NAHR), in the other hand is a recombination between chromosomes that share the same region but at a different locus. It happens between DNA sequences where there is an excess amount of high sequence homology pairs. This occurs less frequent, though it is responsible as a cause for inherited diseases and cancer. Both types for recombination, allelic and non-allelic may cause rearrangement of genome fragments. From exchanging genetic materials of sister chromatids during mitosis or meiosis allow genetic variability, however excess sister chromatid exchange can defect in the DNA regarding the production of proteins, leading to diseases such the Turner's syndrome.

                    Turner syndrome is one possible result of DSB and DNA recombination. The Turner syndrome, or 45(XO) is a phenotype of females that have monosomy X. This means that they only have one X-chromosome instead of two in their genome (45 chromosomes in total). Individuals with Turner’s syndrome are usually short, have broad chest, low-set ears and does not menstruate. It has been found that there is a cluster of inverts repeated sequences in the X chromosome, which is a result from rearrangement from non-allelic homologous recombination.

                    To conclude, the double-strand DNA breaks (DSB) is considered a dangerous process of the DNA replication because one prime side (either 3' or 5') is left free and unprotected. If free-ended DNA is activating, it will interact and intact with other DNA ends. This will result in the genomic fusion and may lead to serious consequences such inherited (syndrome) or somatic origin diseases (cancer). Therefore, DNA repair mechanism is required to repair DNA ends. It's goal is to maintain the balance of genome stability and genome variability to cease possible mutations of the cell. However, DNA repair mechanism can be harmful as well since there are various types of mechanisms (i.e. recombinant vs. non recombinant) which could lead to unique combination of both somatic and sex cell, and result in inherited and/or somatic diseases as well.

[i][ii][iii]

Word Count: 740

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[i] Povirk , Lawrence F. "Processing of Damaged DNA Ends

for Double-Strand Break Repair in Mammalian

Cells." SRN Molecular Biology. Volume 2012

Article ID 345805.16 pages (2012): 1-16. Web. 25

Oct. 2013.

 <http://www.hindawi.com/isrn/molecular.biology/2012/345805/>.

[ii] Genet , Annu Rev. "The role of nonhomologous end-

joining DNA double-strand break repair pathway in

telomere biology." PubMed. (2006): 237-277. Web.

25 Oct. 2013. <http://www.ncbi.nlm.nih.gov/pubmed/16822175>.

[iii] PATHWAY:hsa03450. United States of America:                          

  <http://www.genome.jp/dbget-bin/www_bget?

pathway hsa03450>.

The Golden Rice

The Golden Rice project is a project to genetically modify different species of rice that contains excess amount of betacarotene, where betacarotene is essential to the human diet as a resource of vitamin A.

 I believe that the Golden Rice project should be proceed because it is currently the best type of rice for the third world country. Though the golden rice cannot provide the amount of vitamin A that the body requires, it is still better than providing none. Many people has eye problems, or even more die, from the deficiency of vitamin A. The amount of deaths from the deficiency of vitamin A by proceeding this engineer project, especially in Third World countries. Though it requires a lot of investment to initiate the project, I believe that it is better for the government to spend taxes on aspect that would benefit their society. Profits in the country might be lessen, but it would benefit their population in the long term. Lastly, though the Cons may disagree by saying that if the country only grow one type of rice in their area, the whole population of rice could be lacking due to natural resources according to Darwin's natural selection. This statement is convincing, but it also goes the same to other type of rices that does not provide any amount of vitamin A as well. In fact, since the Golden Rice is genetically modified, I believe that researchers can further modify it so that it can stand different consequences. 

Single-gene and chromosome disorders

 Sexual living organisms have two types of cells: somatic and genetic. Somatic mutation happens with body cells while gametic mutation happens with sex cells and can be pass on to the next generation such as how HIVs are passed on genetically. Mistake from the replication of DNA or the chromosomes can cause mutation and variation in the body. There are two majors way that causes mutation: chemical or radiation and evolving over time to the environment according to Darwin's laws on natural selection.

Chances of DNA failing to replicate the exact  duplicate is really low, however once it has been synthesize wrongly, it could affect the entire individual and lead to mutation or changes in the individual. The modification in autosomes may lead to diseases such as Down syndrome, Edward’s syndrome or fatau's syndrome where there is one extra chromosome (3 chromosomes instead of 2 chromosomes). Since the gene is coded inside the DNA, the disease can be pass on to the next generation as well. In addition, if an individual is missing an autosome, they will result in being handicapped where they might be missing an arm or they might have a volvuli heart disease.

This article on chromosome disorders interested me because I personally know many individual with down syndromes. I think it is pretty amazing how small structure units such as chromosomes have the ability to control and impact the entire living organism.

HAWKSBILL TURTLE

The CITES conference 2013 has been going on in Thailand this past few week where the candidates from different countries gathered together to discuss the issue of whether or not endangered species should be protected. Some find its important to keep these species, while others disagree most likely because whether or not they protect these endangered species, it would not affect their lifestyles in anyway.

Ertmochelys Imbricata, or well known as the Hawksbill Sea Turtle is one of the species that is considered as endangered. They are found in warm sea water and undergoes long distance migrations despite their environment condition. They stand out from other sea turtles with their sharp and curving beak and their saw-like shell. Hawksbills are usually found near coral reefs at feed on sea sponges (high toxic). It takes around 20-40 years to mature therefore its growing and reproductive rate is considered as very gradual.

According to scientists, the hawksbill population has declined for over 80% during the last century.

Hawksbill Turtle is the only species that exists from its genus; Ertnochelys, today and they are considered as a critically endangered animal that has to be conserved due to human impacts. Human, illegally, captures Hawksbill turtles to make jewelry and hunt for their eggs, meats and shells. Despite the pollutions by man, and climate change triggers and destroys their habitat. Hawksbills are very vulnerable to the coral reefs. Once that habitat are being affected from various factors, Hawksbills are also affected by it making them currently the world’s most endanger marine ecosystems.

As for the WCS (Wildlife Conservation Society), they plan to save the hawksbill and other sea turtle species around the world by focusing on the protection of their habitats and their community since it is almost impossible to maintain or reduce the amount of pollution made without people’s will. With the hand from the Convention on International Trade in Endangered Species (CITES), they declared that it is illegal to import or export turtle products, or to kill, harass or hunt for any sea turtles, especially for the hawksbills sea turtle. 

B U T T E R F L I E S ☀

In this week’s three-days weekend, up in the mountain at Khaoyai, there are many different and weird looking insects comparing it to Bangkok, however the organism that seems to attract me most are butterflies. There are plentiful butterflies here but how come all of them with different wings colour even though they fly in the same group; some are red, some are yellow and some are even transparent. One is mainly due to the thickness of their wings. According to my research, butterfly’s wings are covered with thousands of tiny scales that split into two to three layers.

When different light intensity hits the different layers of butterfly wings, different wavelength of visible lights are reflected intensely either in one specific colour spectrum or the combination of spectrums which creates variety of species of butterfly.

Butterfly wings are also capable of communication or camouflage to hide from their predators despite the optical effects we see (rather than a pigment), which allow us to see a particular colour when reacting with light. Butterfly colour also exaplins its evolution and development as well. If someone touches their wings, you might rub off some of the colour on their wings because they are are really delicate and in small scales.

Their wings also need to be at specific range of temperature, or else they will not be able to fly. Since butterflies are cold-blooded, the need the warmth from the sun to enable them to fly.

FLOOOOOOOOD 2011!!

The flood situation in Thailand is like a nightmare for the people. Thailand’s flood in the year 2011 is the most un-expectable event happened in Thailand. From the lack of co-operation and management conflict between the government and the protest as well as the extensive amount of rains and water from the North of Thailand has brought damages to the country badly such as the death of people. However, it is not just people that are irritated and being disturbed by the water, but animals and environment as well. Most animal has to migrate from its location to other places, some died, but some also gets advantages from the flood such as increases of reproduction in mosquitoes, the mambas, and alligators. Most of all, it is like one of the best moment for mosquitoes to reproduce itself and for it to find food (mostly bloods), this is as well called ‘natural selection’, when an animal is able to became fit in a particular environment. In addition, bacteria and viruses have increases more than twice as much from the flood as well. People had been getting an eye infection which may lead them to death or into a blind mode. Doctors and scientists have mentioned that the eyes discoloration is the scariest issue at this moment. They’ve asked parents to avoid their kids from playing in flood water because it is full of bacterial dedicated to the polluted environment. Flood water contains bacteria that are harmful. In addition, bacteria will able to live longer in the polluted environment which equals to the fact that people will have a greater chance of getting those viruses such as red eye. In this case, this infection will circulate badly and quickly and will affect myriad amount of people.

As well, the flood water may cause diseases that allow bacteria to go inside the blood current. The symptom of a boy, nauseated, watery stools admitted into the hospital after playing in the flood water in his neighborhood. The boy shows sign of dehydration and white blood cells are consisted of bacteria coincidentally the same case happened to another boy. Choking may cause the water to enter the boy's body; however doctors have been watching his status closely until he was safe and went home. This is to warn parents that incase any of these symptoms show up please seek immediate medical attention, since the symptoms of nauseating, dehydration, dry lips, tired eyes or watery stool need to be treated with correct medical care.