Junk DNA

Junk DNA

In 1953 Watson and Crick were the first to discover the 3 dimensional helix shape that we now know is DNA. They determined the role of DNA is to transfer heritable features from one generation to the next.  (Campbell, et al. 2009) However within DNA there is a section they called Junk DNA.  This is an area of non-coding nucleic acids called introns. (Campbell, et al. 2009)
Initially Watson and Crick thought the Junk DNA had no real use and dismissed it as non-coding proteins.  However scientists now believe that the non-coding DNA that makes up 95-98% of the human genome has a much more important role than originally thought.

In recent years more and more research is being performed investigating the real role of the junk DNA and these findings are conflicting with original assumptions.  In 2010 scientist set out to explore the relationship between a non-coding stretch of chromosome (9p21) and heart disease. They said that individuals with a nucleotide mutation along this stretch of DNA are at greater risk of suffering from the disease.  The non-coding stretch of DNA was deleted in a group of mice. The results showed the mice that had the DNA deleted actually died earlier or developed tumours when compared with mice that had the stretch of DNA intact.  They concluded that the genes that may have been deleted on the stretch of DNA may control or ultimately inhibit cell proliferation in heart and other tissues. Meaning that without these genes, cells in arteries divide faster which build up causing restriction of blood flow to the heart which causes heart disease. (Visel et al, 2010)



Another idea of the possible functions Junk DNA performs comes from research done on the genomes of fruit flies. The genome of the fruit fly is approximately 80% junk DNA and it seems that the rate in which the flies DNA mutates is far less than what was expected. This means that because of no mutations the evolution of the fly has effectively come to a halt. Furthermore, they go on to say humans and mice have similar genomes, each consisting of around 30,000 genes.  However the species are hugely different. They think that it’s not the genes that separate the species but in fact the junk DNA. Humans have one of the largest proportions of junk DNA out of all species. This may explain the complexity of our species. (Andolfatto, P.  2005)

From recent research it seems to be emerging the idea that junk DNA plays a more important role in human existence than first thought. Whether or not experiments on animals can be applied to humans is yet to be seen. The nature of this type of work has many ethical issues and may take years until experiments on humans are possible. Could it be that one day junk DNA will be considered no longer trash and instead treasure? Only time will tell.

Human and dolphin genomes

Human and dolphin genomes

Humans and dolphins, what do these two animals have in common? You might think that the only thing they could have in common is that they are both mammals. You’re right, but there is a much more interesting fact. Dolphin and human genomes are almost the same. Dr. David Busbee from the Texas A&M University has been involved in a project that studies the genome of dolphins (Kolber, 2010). His team did a number of experiments using hybrid chromosomes combining human and dolphin chromosomes to identify the homologous traits. The results showed that 36 blocks were matching on both species (Fig.1&2). The experiment consisted in “painting” the chromosomes with a fluorescent chemical that would show the homologous traits (Fig.3). Busbee said that he was very surprised when he got to see the results. Because dolphins seem so different animals compared to humans, they live in oceans, eat fish and their physiology is far from ours. However, scientists believe that at some point humans and dolphins came from the same branch of the evolutionary tree. This is shown by the fact that dolphins are mammals that breathe air just like us, so it is believed that initially they were living on land and moved back to the oceans at a later time.

Fig1: Homologies between human and dolphin chromosomes detected by chromosome painting

Fig.2: Matrix showing the distribution of conserved chromosome segments between dolphin  and human

 


Fig.3: Painting of dolphin chromosomes with biotinylates human chromosome-specific paints. Yellow are matching traits.

But how is this discovery useful to science and to us? Evans (2010) discussed that because dolphins have such similarity, they are affected by the same toxins and diseases that affect us. For example, they are affected by red tide toxins, chemicals that are present in wastes which we dump in the sea and other toxins that are present in ocean life. Furthermore, not only have dolphins been affected by the same toxins but they also have learned how to fight or block the effects of these dangerous chemicals. So in other words, if we were able to find out how they are able to have immunization to what affects us, we could use this information to cure or fight the diseases that are caused in humans! For example, we could synthetize a vaccine for diseases. Another important fact is that dolphins can fight type 2 diabetes by simply “switching off” the gene that is affected by the illness and so block the effects of it (Gill, 2010). That would mean that we could cure thousands of people much faster. Another way in which this discovery could help science is that scientists have been studying the dolphin’s genome for years, but with little progress because of lack of resources. But with knowing that it is so similar to our genome it would speed up research by up to 20 years! That would save up a lot of time and money.

Chromosome mutations in yeast cells caused by stress

Chromosome mutations in yeast cells caused by stress

When we consider the concept of evolution, we think of genetic changes in a population over time – perhaps over hundreds or thousands of years. However, some organisms appear to have the ability to genetically evolve in just a few days by inducing chromosome mutations in response to stressful conditions. This phenomenon was studied by a team from the Stowers Institute for Medical Research in 2011. By examining the effects of several stressors, including heat and extreme chemical concentrations, they found that chromosomal variations and consequent drug resistance is the result of the action of heat-shock protein 90 (Hsp90).

In the experiment, yeast cells were submitted to high and low concentrations of a variety of chemicals for 12 to 14 hours. Then, the number of colonies of yeast cells that had an uneven number of chromosomes was compared with the number of colonies with the normal number of chromosomes. Many different stress factors increased chromosomal instability in yeast cells. Most significantly, the result of exposing yeast cells to the drug radicicol, even at a low concentration, was a chromosome loss rate about 300 times higher than the control in stress-free conditions. Exposure to a temperature of 50.9°C produced a similar result.

Graph displaying effects of stress conditions on frequency of colonies that are missing chromosomes

Images displaying effects of stress conditions; red colonies have chromosomal abnormalities

The reason for this surprising result is that radicicol binds to the Hsp90 molecule and disrupts its performance and heat also inhibits the protein. Hsp90 aids the correct duplication of chromosomes during cell division so that the daughter cells contain the same number of chromosomes as the parent cell.When Hsp90 is inhibited, replicated cells are more likely to demonstrate aneuploidy, meaning that they are missing or have an extra copy of a single chromosome.

The genetically diverse colonies of yeast produced by radicicol treatment were then exposed to several different drugs and their performance compared to control colonies. The results showed that the survival rates of the radicicol-treated colonies were much higher against all three drugs.


Images displaying comparison of control yeast colonies and radicicol-treated yeast colonies after exposure to drugs

So how does genetic diversity give a population such an advantage when it comes to survival? Genes within chromosomes determine which proteins are produced in a cell. The number of copies of a gene present in a cell may influence the expression of the gene and thus the final physical characteristics of the organism.For example, four of the yeast colonies that survived exposure to fluconazole demonstrated aneuploidy by containing an extra copy of chromosome 8, and by consequence, an extra copy of the ERG11 gene.This gene helps make organisms more resistant to fluconazole, which normally causes damage to the cell wall of fungal cells.


While the study helps explain one of the mechanisms that make some strains of yeast cells drug resistant, it could be useful in predicting the response of cancer cells to certain treatment. The researchers highlighted similarities between yeast and cancer cells, which often have unusual numbers of chromosomes. This is significant because, previously, some drugs were thought to be able to fight cancer by inhibiting Hsp90 and damaging protein production in the cancer cells.However, these drugs may actually produce drug-resistant cancer cells instead of treating cancer.

Stem Cell Thearpies

Stem Cell Thearpies

Stem cell treatments are a major development in genetic and medical history. Stem cells hold the ability to treat many debilitating illnesses although their uses in treatments raise many ethical debates.

Firstly, let’s define a stem cell. A stem cell is an unspecialised cell that can form specific cells such as a heart, lung or tissue cell. A stem cell is a template for all cells. There are two types of stem cells: pluripotency stem cells and adult stem cells.

Pluripotency stem cells are found in embryos and are therefore named embryonic stem cells. Pluripotency stem cells have the ability to form vast numbers of more specific cells in an embryo, allowing embryos to grow and develop into babies. Because embryonic stem cells hold the ability to form a wide variety of cells, they hold great potential when used in stem cell treatments. However, not all people are in favour of using stem cells in medical treatments.

The embryonic stem cells are derived from fertilised human eggs but are destroyed in the process of Somatic Cell Nuclear Transfer or SCNT.

The process of SCNT involves removing the nucleus of the embryonic stem cell and injecting a nucleus from a different cell into the stem cell. The embryonic stem cell injected with the nucleus from another cell can then be cultivated to regrow the cells from which the nucleus was extracted from. The stem cells grown with the injected nucleus can then be used to replace damage cells. This makes regrowing entire organs and spinal cord tissue possible. This technique was first published by Harvard University in 2008. Some people may find this distressing as they believe SCNT is destroying potential human life.

However, adult stem cells can also be used in stem cell therapy. An adult stem cell is a tissue specific stem cell and can be found in skin, bone marrow, hair follicles and many other sites around the body. Unlike the embryonic stem cells, they are only able to reproduce a specific cell, as the name suggests. For example, an adult stem cell found in the skin can only reproduce to make other skin cells.

Scientists have discovered a technique to make adult stem cells behave like embryonic stem cells. This is called induced pluripotency or iPS. The iPS stem cells have been genetically modified to mimic a pluripotent embryonic stem cell. This is done by using a virus to convert the adult stem cell to behave like an embryonic stem cell and express the genes needed to form the new cell. In 2010, scientists at Standford University have been able to turn fat cells into iPS cells without the use of a virus, making the process of iPS a lot safer and simpler.
The iPS cell treatment is not as controversial as embryonic stem cell treatment but yield the same results, therefore making it a more suitable option in medical treatments.

By using stem cell therapy, illnesses and injuries that may be life threatening or permanently debilitating could one day be treated. With advancing medical and genetic technology, many conditions that were previously thought to be incurable, may well be treatable with stem cell therapies.

Pros and Cons of Designer Babies

Pros and Cons of Designer Babies


Pros:
1.) Designer babies could prevent genetic diseases in babies.
2.) Baby can look and act the way you want it to- hair color, eye color, brains, and athletic ability.
3.) They could, given the knowledge and resources, create an immortal child.
4.) You could see what problems could come for the baby in the future.

Cons:
1.) Everyone could start to look the same, which would cause loss of diversity and culture.
2.) Some people would overuse and abuse their privileges, trying to create the worlds only "genius" or the "ultimate" athlete, parents could choose the life of the child, taking away free will given by God.
3.) It would only help the rich, people who could afford it, and most of the people with genetic diseases in like Africa couldn't afford the help, when they need it more.