#genetic switches – BioQuakes

The epigenome can be effected by pollution

On February 16, 2022

The epigenome is a lesser known part of the study of genetics. It consists of the parts of the genome which are not part of the DNA, for example transcription factors and the accessibility of different sections of the chromatin. DNA in the cell is wrapped around proteins called histones. The wrapping of DNA around these histones are also a factor which controls which parts of the DNA are read into proteins. Furthermore, DNA methylation is an important regulatory factor. The addition of methane groups to DNA makes it impossible to read, effectively shutting off the gene that is methylating.

The epigenome is unique because it can be changed significantly in response to external stimuli. In a way, it is the body’s way of altering DNA on the fly, without actually altering the genetic code. The epigenome can also plays a role in cell differentiation. In class, we discussed how all cells have identical genetic code, passed down from one cell to another. All cells start the same and eventually change into all the different types. The epigenome helps to control exactly which parts of the genome are expressed. It is the epigenome which controls which parts of the genetic code are expressed.

However, the epigenome is still passed down hereditarily and down cell lines. As cells divide through mitosis or meiosis, the epigenome is passed down to the daughter cells. This combination of constant adaptation and persistence through generations make the epigenome an essential part of the body’s function. The combo also makes the epigenome a key part of how the body can be changed for a significant period of time by negative stimuli. These effects can even span generations and have been shown to effect the course of evolution.

Recently, scientists at the University of Liverpool have demonstrated exposure to pollution in water fleas has effects that last over 15 generations. When exposed to a pollutant for a period of 7 months, which encompasses 15 generations of fleas, scientists observed increased rates of DNA methylation. When transferred back to clean water, the scientists found that DNA methylation remained the same. Thus, the pollution permanently damaged the epigenome of the fleas.

Gene Editing in Butterflies: What Could This Mean for Their Mating Patterns ?

By eseffiegus

On March 12, 2019

In Student Post

The beautiful Heliconius butterflies from Central and South Africa are known for their colorful wing patterns. Some of their wing patterns mimic that of other species to protect them from their predators. There is one species of these evolutionary marvels, Heliconius cydno, that scientists have found that the activation of a single gene can determine whether the butterfly expresses white or yellow spots. To come to this conclusion scientists created a genetic map of H.cydno with both white and yellow coloring.

Through examining the genetic maps, the researchers found that the gene al1 was switched on in the white colored butterflies which would mean that al1 gene was correlated to the production of yellow pigmentation. To test this the researchers used CRISPR (a gene editing tool) to switch off the al1 gene in what was supposed to be white spotted butterfly embryo. They found that by switching off that gene the butterflies developed with yellow spots.

The researchers that carried out this experiment also looked into the evolutionary history of these butterflies since this experiment didn’t add pigmentation to the butterflies but changed an ancestrally present pigment by switching off a gene through CRISPR. They studied the al1 gene to butterflies that are closely related to the Heliconius species and found that white version of the spots is a recent development and that H.cyndo was first species to develop the white spots.

After further examination, there was evidence that the white version of the spots corresponds to matting patterns. So, the white spotted H.cydno males preferred to mate with the white spotted H.cyndo females and vise versa with the yellow spotted H.cydno males to H.cydno females. Which begs the question of what roles does the activation of al1 play in not only the coloration of these butterflies but also evolutionarily going forward? If gene activation through CRISPR continues how will that also affect the future mating patterns of these butterflies but possible of other species too?

Microbiome Genes have Macro-significance

By calalyst

On November 8, 2018

In Student Post

Ever been told that the little things matter in life? This same proclamation that you’ve been told by your elders rings true in your gut: one small modification to your human gut microbiome (a batch of bacteria that call your digestive tract home) can have drastic effects on your metabolism.

A. Sloan Devlin, assistant professor at Harvard medical school, carried out a study that proved the importance of the gut microbiome. She first located the gene in “an abundant gut bacterium” for an enzyme that processes bile acids. She then removed that gene from the bacterium. Next, she “colonized” “germ-free” mice with one of two types of the gut bacterium: either with the bile-processing enzyme or without the bile-processing enzyme. The results were surprising.

Credit: mcmurryjulie on pixabay

After both mice were fed the same high-fat, high-sugar diet, the mice without the bile-processing enzyme “had more fat in the liver and gained weight much more slowly than the other group. They also used proportionately less fat and more carbohydrate for energy.” Changing one single enzyme in a gut bacterium appears to change “whether the host is using [primarily] fats versus carbohydrates” for energy.

Even more staggering was the “correlation of lean body mass to energy expenditure.” Typically, in humans and mice, the more lean body mass an organism has, the more energy it expends. However, for the mice without the bile-processing enzyme, this relationship “broke down.” Devlin hypothesizes that this change could be due to a “signaling,” a process in which “physical states in the body trigger a cascade of genes to switch on or off.” Researchers can use this knowledge to treat diseases: figure out which microbiome bacteria activate which genetic switches, and better treatment for genetic problems such as, acid imbalances, metabolic disorders and obesity, may become a reality.

Devlin is sure to stress that this groundbreaking microbiome research is just her “first step.” Although this study was carried out on “germ-free” mice, Devlin dreams that one day she may use her research to improve the health of her own species: as Devlin states, her research brings her “one step closer to humans.”

BioQuakes

AP Biology class blog for discussing current research in Biology

Tag: #genetic switches

The epigenome can be effected by pollution

Gene Editing in Butterflies: What Could This Mean for Their Mating Patterns ?

Microbiome Genes have Macro-significance

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