Friday 22 February 2013

Genetics by Numbers



From the article, you learned about the difficulties (competition, politics, corruption, greed, pursuing of own interests, education, etc) that scientists face in trying to collaborate with each other to obtain the most accurate results. It has been established that the collaboration must be done for future SNP research. Then, how do you think these difficulties can be overcome and will there be further ramifications?
 
Often collaboration between scientists is necessary for advancement such as the research on SNPs as it requires vast data sets. Collaboration between scientists is important because it provides faster results and increases scientific progress. If scientists work together, the work load of the research would be divided and this would allow for more efficient research and faster results. Yet, from the article and class discussions, it is evident scientists face many difficulties when trying to collaborate with each other for instance, greed, competition, money, etc. Competition among scientists is hard to overcome as it is human nature to be competitive. A little sense of competition is ok since it creates motivation in scientists to work harder in order to be the first to discover, publish, and receive credit and grants. However, intense competition creates a barrier to collaboration as scientists would not receive all the recognition and financial grants to themselves.

In order to overcome these difficulties, scientists need to change their view and put aside their greed and understand that science is not about money and publicity but for the greater good of humanity. For instance, scientists could start working in research teams to develop a sense of team work where all the team members work towards SNP research together instead of trying to publish individually. By doing this, scientists would collaborate to benefit society and as a result there would be great advancements in research. Also, international research projects can be created to encourage the collaboration of scientists from different countries. The video on SNP Chip for the Sheep Genome is a good example of SNP international collaboration. To produce the SNP chip, nineteen countries collaborated, with each country playing a role in part of the research process to contribute to a piece of the puzzle. In addition, the funding for the research was shared as well. Together, these countries were able to create a pool of resources and developed a SNP chip.

This shows that it is in fact possible for scientists to overcome competitiveness and collaborate for the common good of science and society. However, this is hard to achieve in the science community as money and corruption tend to come in the way of collaboration.

 

Monday 18 February 2013

Transcription and Translation


 


Genetic information is transferred from DNA to RNA to protein. There are two steps in this process, transcription and translation.


Transcription:
  • The synthesis of RNA from a DNA template.

Initiation:
  • Only one strand of DNA is transcribed. This strand is called the template strand. The other strand is not transcribed and is called the coding strand. The coding strand has the same sequence as the product mRNA except it has thymine instead of uracil .

  • RNA polymerase: The main enzyme that catalyzes the synthesis of RNA from a DNA template. Promoter region: The RNA polymerase binds to a promoter region on the DNA which consists of a sequence of nucleotides that show the RNA polymerase where to initiate transcription.

  • Two promoter sequences are required to show the RNA polymerase complex the correct strand for binding and the correct orientation.

  • After binding to the DNA, the RNA polymerase unwinds and opens a section of the DNA.
Elongation:
  • RNA polymerase synthesizes mRNA that is complementary to the template strand of DNA with the T being replace with U. The RNA polymerase add new nucleotide to the 3'-OH group moving in the 5'to 3' direction but since only one strand of template DNA is being synthesized  in one direction, Okazaki fragments are not needed.

  • While one RNA polymerase moves along the DNA, another RNA polymerase binds to the promoter region synthesizing another mRNA molecule. This allows hundreds of copies of nRNA molecules to be made from one gene at a time.

  • Synthesis of mRNA occurs at a faster rate than synthesis of DNA because RNA polymerase does not have a proofreading function. An error in transcription only results an error in one protein molecule, not in the genetic make-up of organism and therefore is not significant. Synthesizing mRNA at a higher speed is more important than minimizing sequence errors.
                                             
Termination:
  • Specific nucleotide sequences in template DNA signal the stop of transcription. When RNA polymerases reaches this signal it detaches from the DNA strand.
  • The new mRNA strand is released and the DNA double helix rewinds.
  • A G-cap is added on the 5'end and a poly-A tail at the 3'end to make the mRNA stable.
Translation:
  • The next step is translation where mRNA template is used to produce proteins with amino acid sequences.
Initiation:
  • Proteins called initiation factors assemble small and large ribosomal sub-units, mRNA, and initiator tRNA.

  • The small ribosomal subunit binds to mRNA near the start codon (AUG). Then, the initiator tRNA carrying an amino acid binds to the mRNA start codon with its complementary anticodon (UAC) and the corresponding amino acid methionine.

  • The large ribosomal subunit joins to form the ribosome and starts the process. There are three binding sites for the tRNAs: the P(peptide) site, A(amino acid) site, and E(exit) site with the initiator tRNA occupying the P site and the A site ready for the next tRNA.
Elongation: (4 Steps)
  • With the initiator tRNA occupying the P site, the next tRNA carrying second amino acid enters the A site. Elongation factors enable the tRNA anticodons to bind to mRNA condons.

  • A peptide bond forms between the first and amino acid and the amino acid in the A site and the chain transfers from the initiator tRNA to the new tRNA at the A site. The resulting dipeptide is attached to the tRNA at the A site.

  • The polypeptide chain is one amino acid longer nad the mRNA moves ahead by one codon and the tRNA goes to the P site.  

  • The tRNA no longer carries its amino acid and exits from the E site.The new codon is at the A site ready to receive the new complementary tRNA.
                      3typesofRNA.png
Termination:
  • Elongation continues until the mRNA reaches a stop codon (with the codon sequences UAG, UGA, or UAA).

  • A protein called a release factor cuts the polypeptide chain from the last tRNA.

  • The polypeptide is released and folds into a three-dimensional shape ready to carry out its activities.

Sunday 10 February 2013

Deaf by Design Response

After having Mr.Chung present to us the Nature article Deaf by Design and the video Sound and Fury,here are some discussion question that we had to think about and respond to:  
 
Is it more of a blessing or a curse to have the ability to alter our genetic codes?
The ability to alter genetic codes is a blessing because it gives the option to make positive changes that would not have been possible in the past and prevents people from the suffering of chronic diseases and conditions. However, this ability can be a curse since it creates many ethical issues as to when it is acceptable and when it is misuse. It is our decision to choose how this ability is used.

Do the deaf have as much right as the rest of us to abort a fetus that is, in their view, disabled?
It is understandable why a deaf couple would want to abort a hearing, healthy fetus; it would be difficult to understand and raise a hearing child and there would be a gap in the relationship between the deaf parents and the hearing child. However, this is not a justified reason to abort a fetus. Abortion in cases where the fetus has a disability such as fatal health issues or serious physical/mental conditions be justified since it would avoid the fetus from the suffering that he/she would face if born. A healthy and hearing fetus should live because he/she has potential to live an average life. I find that aborting a hearing fetus would be selfish since it seems to be more towards the parents’ best interest rather than the child’s. Similarly, I think it’s not right for hearing parents to abort a deaf child either because in both cases, the “disability” does not restrain the child’s future. I believe that both for the hearing and deaf, it is only under fatal or extreme conditions where abortion of the fetus should be acceptable.

Is "disability" a relative term? What constitutes a person's disability?
Disability is a relative term because a disability can turn into an advantage in certain situations just like certain traits can turn into a disability in different situations. It is important to note that “normal” is a relative term as well. In the deaf community, the deaf consider themselves as normal and hearing is considered a disability. What is disability defined as? According to Oxford dictionary, disability is a physical or mental condition that limits a person’s movements, senses, or activities. Basically, any trait that limits a person from doing certain tasks that an average person would be able to do can be defined as disability, such as deafness.

Is it Heather's best interest to be raised as the only hearing child in the family?
I think that it is not Heather’s best interest to be raised as the only hearing child in her family. Being the only hearing child in her family would have a negative impact on Heather since all her family members are deaf. If Heather becomes the only hearing person in the family, she would feel disconnected from her family and her relationship with her family members, especially the parents, would become distant. Heather’s father has a strong opinion about the deaf culture and feels that hearing prevent Heather from fitting into the deaf culture. If Heather becomes hearing, it is going to destruct her relationship with her father. Also, hearing may weaken her bond with the deaf community since the deaf share strong emotional bonds compared to the hearing. At her age, Heather needs full support from her parents and she might lose her cultural identity if she becomes hearing. Heather is a bright child and she would have a successful future without having to hear. Also, thanks to modern technology, she would have other ways to communicate without using sign language such as texting. Therefore, it is Heather’s best interest to not receive an implant.