BioQuakes

AP Biology class blog for discussing current research in Biology

Tag: gene variants

What is the Real Reason Dog Breeds Vary in Size?

Dog (Canis lupus familiaris) (6)

Do you like big dogs or small dogs? This question is frequently asked, but how did we even come about having this option? Ancient domesticated dogs in the past 30,000 years differed in size but nothing as extreme as the modern size differences. Dogs now can range from 40 times in size, and these drastic differences emerged just in the past 200 years as humans started establishing more and more breeds. In a study conducted by Ewen Callaway, he looked at why dogs differ so much in size and how a mutation could be the cause of this. The mutation behind all of this has been traced all the way back to ancient wolves. It lies near a gene called IGF1(insulin growth factor) which researchers found to have a major role in the size variations of domestic dogs. IGF1 is a hormone that manages the effects of growth hormones and is primarily produced by the liver so liver diseases can cause its levels to change.

One variant stood out when comparing the region around IGF1 and dog sizes. This variant “lies in the stretch of DNA that encodes a molecule called a long non-coding RNA which lives in controlling levels of the IGF1 protein.” A gene variant is a permanent change in the DNA sequence that makes up a gene. Variants can be inherited from a parent or can just occur during a person’s lifetime. If a variant is inherited from a parent they are present in pretty much every cell of the body while a variant that occurs during someone’s lifetime is present only in certain cells. Most variants that lead to disease are not common in the general population; however, some variants occur often enough in the general population to be considered common genetic variations. Examples of this would be eye color, hair color, and blood type. Even though DNA variants can be seen as a negative, as it is explained not all variants produce fatalistic effects.

There are two identified versions (alleles) of the variant, which Callaway identified. An allele is a form of a gene and each organism inherits two alleles, one from each parent. Dogs who have two copies of one allele typically weigh more than 55 pounds and have higher IGF1 protein levels in their blood. Whereas, dogs with two copies of the other allele tend to weigh less than 33 pounds. In addition, there are dogs with one copy of each version and they tend to be intermediate in size. Researchers determined that the same relationship was present in other canids as well, such as foxes, coyotes, and wolves.

Protein IGF1R PDB 1igr

IGF1 structure

The allele linked to small-bodied animals is seen to be much more evolutionary than alleles linked to large-bodied animals. Coyotes, jackals, foxes, and a lot of other candids have two copies of the small version, suggesting that this variation could have been present in their ancestors. However, it is not as clear as to when the large-bodied allele formed. It has been traced back 53,000 years ago to an ancient wolf living in Siberia, and since then has been found in other ancient wolves. Robert Wayne, an evolutionary biologist at UCLA, states that the view used to be that animals that have a small body size can be linked to genetic changes that could be unique to domestic dogs. This study could be a sign that dogs were domesticated from smaller wolves rather than present-day gray wolves.

Overall researchers have discovered a big part as to why dogs vary so much in size, however, the story of dog size is far from complete as IGF1 proteins only make up 15% of the difference in dog size. Even though this is such a small percentage, we are 85% closer to finding the whole meaning.

“US braces for Omicron!”…Whats all the hubbub really about?

I was studying for AP Bio one day, when I first heard about the fears around the omicron variant. All over instagram, facebook, I even received emails about it: there seems to be major concern among many, including prominent medical researchers, according to WHO.

World Health Organization Logo

“What is the omicron variant?” You may ask.  This variant was first reported from South Africa  Wednesday, November 24th. In the recent weeks, cases of infection have been increasing rapidly in South Africa, likely as a result of this mutated variant. According to WHO, this variant has a large number of concerning mutations (discussed in detail below), some of which increase the risk of infection. Luckily, current SARS-CoV-2 PCR tests still can be used as a marker in detecting this new omicron variant. Because of this fact, officials have been able to detect this variant faster than previous surges in infection cases.

OmicronDespite being able to detect this variant faster than previously, researchers are still concerned over the mutations this variant poses and the implications that could have in this pandemic. Being the fastest spreading variant yet, some of these concerns include the specific mutations on the spike proteins. As we learned before, Spike Proteins protrude from the SARS-CoV-2 cell, allowing for it to bind to receptors on the host cell. Penny Moore, a virologist at the University of the Witwatersrand in Johannesburg, South Africa, says there are more than 30 mutations to the spike protein in omicron, which could possibly make it more contagious and/or allow this variant to evade our vaccines. 

Many of the mutations detected on the omicron variant have been found in the delta and Alpha variants, and are linked to heightened infections, as well as the ability to evade infection-blocking antibodies and other immune responses. Mutations to regions of the spike protein in the omicron variant has changed the way the antibodies recognize the pathogens, hindering their ability to bind to the spike proteins. If the spike proteins have mutated and changed shape, then the antibodies will not be as effective in binding. Additionally, hints from computer modeling have revealed the omicron variant could dodge the immunity given by the T cells. However, Scientists have yet to understand the true significance of these mutations and what it means for the response to the pandemic. Penny Moore and her team hope to have their first results in two weeks. 

What does this mean for vaccine efficacy?

Solo-mrna-vaccine-4 Well, two quarantined travelers in Hong Kong have tested positive for the omicron variant despite being vaccinated using the Pfizer vaccine. Additionally, Moore says that breakthrough infections have been reported in South Africa among people who have received the vaccine. Again, researchers in South Africa will soon find whether this omicron variant causes illness that is more severe or milder than that produced by the other variants. We should hear their results soon. According to Researchers, the greater threat that this omicron variant poses beyond South Africa is unclear. In the meantime, a way to fight for a healthy future would be to continually take the measures necessary to reduce the risk of COVID-19, including proven public health measures such as wearing masks, hand hygiene, social distancing, and getting vaccinated.

Let me know your thoughts below on this new variant! Stay Safe!

 

Is it Really Your Choice to Make Better Choices?

diet-398613_960_720

Picture of scale (licensing information here)

Obesity has become an increasingly prevalent epidemic around the globe and especially in the United States. Obesity has numerous roots. Recently, researchers from the McGill Centre for the Convergence of Health and Economics found that in some circumstances, it is possible to blame obesity not solely on genetic make-up, but rather on genetic make-up and socio-economic background combined. The McGill researchers discovered that the fat intake of a female who is a carrier of DRD4 VNTR with 7 repeats, a specific gene variant, is determined by the interaction of the female’s socio-economic environment with the gene. This gene variant affects about 20% of the population and is commonly related to obesity, especially in females. Males are typically not as affected by the gene because when comparing males and females at the same age, males do not typically show the same pattern of food preferences.

In order to research this topic, McGill researchers randomly selected about 200 Canadian children with an average age of 4 from the MAVAN birth cohort in Montreal, Quebec and Hamilton, Ontario to take place in the experiment. The McGill researchers used food diaries kept by the parents of every child in order to determine what was being eaten and how often the child was fed. The researchers were able to calculate the percentages of fat, protein, and carbohydrates the children were consuming, as well as the BMI of every child. Since the children were selected at random, the researchers tested every child for the gene variant using a saliva test. The researchers also analyzed the socio-economic background of every child and availability of particular foods based off of the family’s income.

Laurette Dubé, Scientific Director at this particular Centre at McGill and lead researcher on the study, analyzed the results. Dubé found that when comparing two females from the same socio-economic background, one with the gene variant and one without, the female with the gene variant had a higher fat intake, even though the two females came from the same socio-economic background. She also discovered that when comparing two females with the gene variant, one coming from a wealthy family and one coming from a poor family, the female coming from the poorer family had a higher fat intake, despite the fact the two females were both carriers of the gene variant. This newly found research led the McGill research team to believe that the gene alone does not determine an individual’s fat intake, but instead the gene causes an individual to be more sensitive to his or typically her environmental conditions that determine what are “good” eating patterns and what are “bad” eating patterns. Dr. Robert Levitan, co-invesitgator on the project, leader of the childhood obesity program of the MAVAN cohort, and Senior Scientist at the Centre for Addiction and Mental Health (CAMH), is an expert on the DRD4 gene in adult female “overeaters”. Levitan said, “We previously assumed that the 7-repeat variant caused weight gain in these patients by increasing the rewarding aspects of certain foods. These new results suggest a different way that the gene might affect food choices” (Biology News).

In certain cases, obesity isn’t all about genetic make-up, but the likeliness of obesity is determined by the socio-economic background of an individual as well! So, if you are a carrier of the DRD4 VNTR with 7 repeats gene variant, which, because of your environment, impacts your decisions, is it really your choice to make better choices?

Source: Biology News 

 

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