The population problem

known as Irrc10 and caveolin, were much more active in the river fish following heart injury. Scientists then experimented on Zebrafish, a different species with healing abilities, and turned off the Irrc10 gene. They found that without this particular gene, the Zebrafish was unable to fully repair its heart without scarring. Scar tissue prevents the heart from functioning properly because it reduces its ability to pump blood. Irrc10 and Caveolin are present in humans, and Irrc10 is actually related to a medical condition known as dilated cardiomyopathy. Further research into these genes could seriously benefit the treatment of people with heart conditions. At the moment the only treatment is a heart transplant which does not have guaranteed success because the body could easily reject it and attack the new heart cells. The blind form of this incredible fish is also extremely important for future groundbreaking science. Roughly 1.5 million years ago, some Mexican river tetras, living in the Northern Mexican rivers, got washed into caves by floodwaters and became trapped there. So what did they do? They adapted. These tetras lost the pigmentation in their skin and they lost their eyesight due to the permanent darkness that surrounded them. Some had only partial eyesight and others went completely blind or even without eyes. They have even adapted to have a better sense of smell via taste buds all over their heads, which allows them to find food more easily. These cave dwelling tetras are able to store four times more energy than the river dwelling tetras, and they store it in the form of fat. This adaptation enables the fish to deal with inconsistent food supplies of algae in the cave more efficiently. Sources say that because of such a “sudden environmental change, their phenotypic (characteristic) evolution occurred more rapidly within about 20 000 years and is probably still ongoing.” Although 20 000 years doesn’t seem very fast to us, when compared to other animals such as the giraffe, which supposedly didn’t fully evolve to be truly long necked until 7.5 million years ago, that is a very fast adaptation.

Scientists are also very interested in this adaptation of the fish because it could lead to a medical breakthrough for people with type two diabetes. A quote from an article in the National Geographic: “When people have high blood glucose, the sugars in our cells are essentially coated with sugar, causing them to malfunction.” “These cavefish have high blood sugar, but no sugar coated proteins.” This is because they have uniquely adapted to be able to regulate their blood sugar levels, and when geneticists used the gene sequencing tool called CRISPR, they found that the fish had adapted to be Insulin resistant. As you may know, Insulin is fundamental in the process of turning blood sugar, from the food we eat, into energy. In people with type two diabetes, their insulin is neither working properly nor is there enough of it being produced. Likewise, these blind cave fish also experience elevated levels of blood sugar yet they have remarkably few health impacts from it. According to sources I have found, hybrids have actually been made between the river fish and the cave fish, and sure enough the offspring turned out “expectedly chubby and showed high glucose levels.” Geneticists have also been able to insert this insulin

resistant mutation into some Zebrafish. Their results were positive and showed that the Zebrafish also gained weight and became insulin resistant. Researchers believe that further information on how these fish manage to live healthily with such high levels of blood sugar could massively benefit those affected with type two diabetes. So you have now read about how amazing the genetic information from these tetras could be, but how do you actually extract these genes and find out more about them? Well, as I mentioned before, scientists are now using a gene editing tool known as CRISPR Cas9. DNA is made up of 4 building blocks called bases which are strung together in special sequences that instructs each cell on what to do and forms the coding behind our every trait. CRISPR technology actually originated from a natural process that has functioned as a bacterial immune system for millions of years, protecting single-celled bacteria and archaea against invading viruses. The first of the two components are short snippets of repetitive DNA sequences called “Clustered Regularly Interspaced Short Palindromic Repeats”, also known as CRISPR. The second of the two components are Cas, also known as CRISPR associated proteins, which cut up DNA like molecular scissors. If a virus invades a bacterial cell, the Cas proteins cut out a segment of the viral DNA and add it into the CRISPR region, almost like a scrapbook. These viral codes are next transferred into short pieces of RNA, which stands for ribonucleic acid, and binds to a special protein called Cas9. This composite latches onto free-floating genetic material This defence mechanism works in many different types of bacteria, but in 2012, scientists figured out how to hijack CRISPR to target any DNA in almost any organism! In the lab, the scientists first design a “guide” RNA to match the gene they want to edit. They then attach the “guide” RNA to Cas9 which tells Cas9 which gene to target. Cas9 then snips the DNA which matches the “guide”. Just by attaching this “guide” RNA to Cas9, scientists can practically edit any gene in the genome. After the DNA has been cut the cell tries to repair itself by trimming the broken ends and joining them back together. This type of repair process is called nonhomologous end joining and is apparently prone to mistakes such as extra or missing bases. This makes the gene unusable and usually gets turned off. However, if scientists add in a DNA template, the proteins can carry out homology directed repair. This guide allows the rebuilding process of a defective gene or even creation of an entirely new one. Although CRISPR is such an amazing tool, it does not always make the exact changes that we want. This makes it difficult to predict some of the long term effects that CRISPR gene editing will have and raises a lot of questions about what is ethically right and wrong. But, we should always try and explore further into the science behind things and this tool is potentially the key to creating cures for the genetic diseases putting many lives in danger.

By Katherine Marriott Year 10 Scientists have spent decades pondering on how we can solve the world’s population problem. Many questions arise when answering this, is it better to have overpopulation or underpopulation? Can we really solve this problem?In the world we live in today, there are numerous problems in the field of earth's population. From insect colonisation of habitats, to poor living conditions, population can influence quality of life on any spectrum. A historical example of the problem with a country having a large population would have to be China’s infamous one child policy, which remains to be a staple in discussions on population, mainly due to the economic, social and political consequences. By 1949, China’s government sporadically began promoting family planning and the use of birth control, until after the death of Mao Zedong in 1976. Around this time China’s population was close to the 1 billion benchmark, but then under the leadership of Deng Xiaoping, pragmatic steps were taken to “solve the population problem”, in 1978 a voluntary program was introduced, with the aim to encourage families to have no more than two children. This escalated in 1979 the demand grew for families to stick to one child, however this policy was nationalised in 1980 on the 25th of September in the form of a public letter published by the central committee of the Chinese communist party. Although there were several exceptions, this policy was applied universally (implemented more harshly in urban environments, if the first-born child was handicapped). Contraceptives were offered, and citizens who complied were treated better, and those who wouldn’t follow the rules were forced to have abortions and recieve sterilisations (primarily women). Subsequently, there were many consequences that went beyond the goal of reducing the population. The most notable reprecution is the sex ratio. There were between 3 and 4 percent more males than females living in China, as a result of males being the more prefereable sex and females being frequently aborted or adopted into families overseas. This proved to be a problem as this became difficult as there were fewer females available for marriage. Another major problem was the glowing elderly population which relied on the younger generations to survive. The amount of people hidden from the government grew massively, although the exact number is not known, it is estimated to be around the hundreds of thousands to millions. This program came to an end in 2015, though the consequences left an impact for much longer.