Understanding Non-Mendelian Genetics (Patterns of Inheritance)
Genetics is an expansive field that focuses on the study of genes. Scientists who specialize in genetics are called geneticists. Geneticists study many different topics, including:
how genes are inherited from our parents
how DNA and genes vary between different people and populations
how genes interact with factors both inside and outside of the body
If you're looking into more information on genetics topics, you may come across two types of genetics: Mendelian and non-Mendelian genetics.
This article reviews both types of genetics, with a focus on non-Mendelian genetics. Continue reading to learn more.
What is Mendelian genetics?
It's possible that you may remember some concepts of Mendelian genetics from your high school biology class. If you've ever done a Punnett square, you've learned about Mendelian genetics.
The principles of Mendelian genetics were established by the Austrian monk Gregor Mendel in the mid-19th century based on his experiments with pea plants.
Through his experiments, Mendel pinpointed how certain traits (such as pea color) are passed down across generations. From this information, he developed the following three laws, which are the basis of Mendelian genetics:
Dominance. Some variants of a gene, called alleles, are dominant over others. Non-dominant alleles are referred to as recessive. If both a dominant and recessive allele are inherited, the dominant trait will be the one that shows.
Segregation. Offspring inherit one allele for a gene from each of their parents. These alleles are passed down randomly.
Independent assortment. Genetic traits are inherited independently of each other.
Pea color: An example of Mendelian genetics at work
To illustrate how Mendelian genetics works, let's use an example with pea plants, in which yellow pea color (Y) is dominant and green pea color (y) is recessive.
In this particular example, each parent pea plant is heterozygous, meaning it has a dominant and recessive allele, noted as Yy.
When these two plants are bred, noted as Yy x Yy, the following pattern of inheritance will be seen:
25% of offspring will be homozygous dominant (YY) and have yellow peas.
50% of offspring will be heterozygous (Yy) and have yellow peas.
25% of offspring will be homozygous recessive (yy) and have green peas.
What are examples of health conditions that follow Mendelian patterns of inheritance?
There are several health conditions that follow Mendelian patterns of inheritance.
Alleles for sickle cell anemia and cystic fibrosis are recessive. This means that you need two copies of the recessive allele, one from each parent, to have these conditions.
In contrast, the allele for Huntington's disease is dominant. That means that you only need a single copy of the allele (from one of your parents) to have it.
Sex-linked conditions
Some health conditions can be linked to genes in the sex chromosomes (X and Y). For example, hemophilia is X-linked recessive.
In those assigned male at birth, who have a single X chromosome, only one copy of the recessive allele is enough to have hemophilia. That's why hemophilia is more common in males.
Individuals assigned female at birth have two X chromosomes, meaning they need two copies of the recessive allele to have hemophilia.
What are non-Mendelian genetics?
Exceptions exist for every rule, and that's also true for genetics. Simply put, non-Mendelian genetics refers to inheritance patterns that don't follow Mendel's laws.
Here are some different types of non-Mendelian genetics:
Polygenic traits
Some traits are determined by two or more genes instead of just one. These are called polygenic traits and don't follow Mendelian inheritance patterns.
Examples of polygenic health conditions include:
hypertension
diabetes
certain cancers, such as breast and prostate cancer
Mitochondrial inheritance
Your mitochondria are the energy factories of your cells and also contain their own DNA, called mtDNA. While there are some exceptions, mtDNA is usually inherited from your mother.
You get your mtDNA from your mother because the mitochondria present in sperm typically degrade after fertilization. This leaves behind just the mitochondria in the egg.
Examples of Mitochondrial health conditions include Leber hereditary optic neuropathy (LHON) and mitochondrial encephalomyopathy.
Epigenetic inheritance
Epigenetics refers to how genes are expressed and regulated by factors outside of the DNA sequence. This includes things like DNA methylation, in which a chemical called a methyl group is added to a gene, turning it 'on' or 'off'.
Epigenetic factors can change as we get older and are exposed to different things in our environment. Sometimes, these changes can be passed down to the next generation, which is called epigenetic inheritance.
Certain cancers (such as breast, colorectal, and esophageal cancer) have been linked to epigenetic changes. Neurological disorders like Alzheimer's and metabolic diseases like Type 2 diabetes have also been associated with epigenetic inheritance.
Genetic imprinting
While we inherit two copies of a gene, one from each parent, in some cases, only one copy of the gene may be turned 'on' via DNA methylation. This is called imprinting, and it only affects a small percentage of our genes.
Which gene is turned 'on' can depend on where the gene came from. For example, some genes are only turned 'on' when they come from the egg, while others are only 'on' when they come from the sperm.
Examples of conditions associated with genetic imprinting include Beckwith-Wiedemann syndrome, Silver-Russell syndrome, and Transient Neonatal Diabetes Mellitus.
Gene conversion
Gene conversion can happen during meiosis, the type of cell division that helps make sperm and eggs. After meiosis, each sperm and egg contains one set of chromosomes and therefore one set of alleles to be passed down to offspring.
During meiosis, genetic information from one copy of an allele (the donor) may be transferred to the corresponding allele (the recipient). This results in a genetic change that effectively converts the recipient allele to the donor allele.
Genetic conditions influenced by gene conversions include hemophilia A, sickle cell disease, and congenital adrenal hyperplasia.
What are examples of health conditions that follow non-Mendelian patterns of inheritance?
Most health conditions we're familiar with don't follow Mendelian inheritance patterns. These conditions are often polygenic, meaning the effects of multiple genes contribute to them.
For example, cystic fibrosis is caused by inheriting two copies of a recessive allele of a specific gene. However, there's not an isolated 'heart disease' allele that we inherit that causes us to develop heart disease.
Mitochondrial disorders, which are caused by changes in mtDNA, are another type of health condition that follows non-Mendelian patterns of inheritance. This is because you typically inherit mtDNA from your mother.
Sometimes problems with genetic imprinting can lead to disorders. Prader-Willi syndrome and Beckwith-Wiedemann syndrome are two examples.
How do Mendelian and non-Mendelian genetics contribute to our understanding of genetic diseases in humans?
Understanding both Mendelian and non-Mendelian inheritance patterns is important in understanding how different genetic diseases may be passed down.
For example, if you have a certain genetic disease or you know that one runs in your family, you may have concerns about future children inheriting it.
In this situation, working with a medical professional, such as a genetic counselor, who understands a disease's inheritance patterns can help you get an understanding of the risk of future children having the disease.
Additionally, understanding genetic changes and inheritance can affect future therapies. This information can be important for developing gene therapies for a variety of genetic diseases.
Takeaway
Mendelian genetics focuses on the principles that there are dominant and recessive alleles and that we randomly inherit one copy of an allele from each parent.
Some health conditions follow basic Mendelian inheritance patterns. Examples include cystic fibrosis and Huntington's disease.
Non-Mendelian genetics don't follow the principles outlined by Mendel.
Many health conditions we're familiar with don't follow Mendelian inheritance patterns because they're polygenic, affect mtDNA, or are associated with imprinting.
Hashtags
Try Our AI Features
Explore what Daily8 AI can do for you:
Comments
No comments yet...
Related Articles
Yahoo
5 hours ago
- Yahoo
Experts issue warning as 'alien monster' spider spreads around the globe on cargo ships — here's why it's so dangerous
Experts issue warning as 'alien monster' spider spreads around the globe on cargo ships — here's why it's so dangerous Australia may soon be invaded by a spider that scientists have called an "alien monster." What's happening? The New Zealand false widow spider, a native of the Canary Islands and Madeira in Spain, is an invasive species that is spreading rapidly via cargo shipments. According to the International Business Times, the spider that scientists have labeled an "alien monster" is believed to be making its way to Australia. The false widow is known for adapting well to urban environments and can be found everywhere from mailboxes to garden sheds, so it will thrive in areas of Australia with similar environments. However, this invasive species offers a double whammy with its bites, which is what earned it the label of "alien monster." Though the species is less aggressive than some other spiders found in Australia, its venom is neurotoxic and can cause swelling, pain, tissue necrosis, and low blood pressure. Fatalities from the bite of this spider are rare; however, hospitalizations are not. Even worse, though, is the fact that the false widow spider is a host for a plethora of antibiotic-resistant pathogens, meaning antibiotics don't always work on bites from this species. Why are invasive species concerning? Any kind of invasive species is a major concern for the country it invades, as they can cause immense damage to native species and local ecosystems. As evidenced by the false widow spider in New Zealand, invasive species spread rapidly. They outcompete native species for vital resources, such as food, and introduce new diseases into local populations (or in this case, new neurotoxins and antibiotic-resistant pathogens). Some invasive species can also impact human food supplies, destroy native plants, alter soil chemistry, and even exacerbate extreme weather conditions. Protecting and prioritizing native species is a crucial way to help conserve natural resources, safeguard food supplies for both animals and humans, and limit the spread of new diseases. Do you worry about air pollution in your town? All the time Often Only sometimes Never Click your choice to see results and speak your mind. What's being done about the New Zealand false widow spider? Unfortunately, there's only so much that experts can do to stymie the tide when it comes to invasive species, especially in cases like this one where the species is small and can hide in cargo to enter the country. According to IBT, experts in Australia have urged the government to increase the monitoring of imported goods, educate the public about the species, and make investments in containment measures to mitigate the risks associated with the false widow spider. Join our free newsletter for good news and useful tips, and don't miss this cool list of easy ways to help yourself while helping the planet. Solve the daily Crossword
Yahoo
6 hours ago
- Yahoo
Why does your mind goes 'blank'? New brain scans reveal the surprising answer
When you buy through links on our articles, Future and its syndication partners may earn a commission. You look up from your phone screen and suddenly realize you weren't thinking about anything. It's not a lapse in memory or a daydream; it's literally a moment when you're not thinking of anything at all. Neuroscientists have a term for it — mind blanking — which they define as a brief, waking state when conscious thought simply stops. Scientists used to think our waking minds were always generating thoughts, but recent research shows that's not the case. Mind blanking is now recognized as a distinct conscious state associated with changes in arousal, which in neuroscience refers to alertness and responsiveness to stimuli. Studying this curious state could shed light on how consciousness works, some researchers think. "For some, it's kind of a blip in the mind, and suddenly there's nothing," Thomas Andrillon, a neuroscience researcher at the French National Institute of Health and Medical Research and the Paris Brain Institute, told Live Science. "But not with that feeling, 'There was something that I forgot.'" Often, people are unaware of the lapse until they are prompted to answer "What were you just thinking about?" "When we interrupt them randomly," Andrillon continued, "it's clear it's more frequent than what people realize." Although the frequency of this phenomenon varies among individuals, various studies suggest about 5% to 20% of a person's waking hours may be spent in this state. Related: Super-detailed map of brain cells that keep us awake could improve our understanding of consciousness An investigation of 'mind blanking' In a study published in the July issue of the journal Trends in Cognitive Sciences, Andrillon and his team used electroencephalography (EEG) — which involves placing electrodes on participants' heads — to measure brain activity while people experienced lapses in attention, such as mind wandering or mind blanking. Mind wandering occurs when people's thoughts drift to tasks or ideas unrelated to the one at hand, while mind blanking involves the absence of all thought. While wearing EEG caps, participants watched numbers flash rapidly on a display screen. They were instructed to press a button every time a number appeared except for 3, which they were told to skip. This task tests how quickly people react when a response is required and how well they can inhibit that response, when necessary. Because most of the presented numbers required a response, people often pressed the button by mistake when they saw a 3 onscreen. The researchers paused the task once a minute to ask what the participants were thinking, finding that they were either focused on the task, their mind was wandering, or they were experiencing a "mind blank." Participants pressed the button more quickly when their minds were wandering, whereas their responses slowed noticeably during mind blanking, suggesting these two mental states are distinct. Brain activity told a similar story. The EEG data showed that the participants' brain activity tended to slow down slightly more when their minds were blank than when they were wandering, compared to the baseline of their paying attention. 'The connectivity changes as if the inner workings of the brain were specific, in a way, to that state," Andrillion said. EEG data is great for tracking rapid changes in brain activity, but it can't pinpoint exactly which brain regions are involved. That's in part because it records brain waves through the skull, and the signals blur as they make their way through the brain tissue, fluid and bone. Andrillon explained it's like listening through a wall. You can tell if a group inside is noisy or quiet, but you can't tell who is talking. The EEG results from the study suggest that during mind blanking, the brain's activity slows down globally, but the technique couldn't identify specific areas. That's where functional MRI (fMRI) came in. Related: 'Hyper-synchronized' brain waves may explain why different psychedelics have similar effects, rat study reveals Hypersynchronization fMRI provides a clearer view of which regions are active and how they interact, but its tracking speed is slower because the technique tracks bloodflow, rather than directly following brain signals. fMRI is more like peeking into the room and seeing who's talking to whom, but not knowing precisely when, Andrillion said. Study co-author Athena Demertzi, a neuroscience researcher at the GIGA Institute-CRC Human Imaging Center at the University of Liège in Belgium, led the fMRI portion of the study. As people rested in an fMRI scanner with no particular task at hand, Demertzi and her team periodically asked what they were thinking. The results were surprising: when people reported mind blanking, their brains showed hyperconnectivity — a global, synchronized activity pattern similar to that seen in deep sleep. Typically, when we are awake and conscious, our brain regions are connected and communicating but not synchronized, as they appear to be during mind blanks. "What we think happens in the case of mind blanking is that the brain is pushed a little bit toward the side of synchronization," Andrillon said. "That might be enough to disrupt these sweet spots of consciousness, sending our mind to blank." Research into mind blanking is still in its early stages, but Andrillon and Demertzi noted that its similarity to brain patterns seen during deep sleep may offer an important clue as to its function. Deep sleep, also known as slow-wave sleep, coincides with important cleanup work for the brain. It clears away accumulated waste, cools the brain, conserves energy and helps reset the system after a full day of mental activity. RELATED STORIES —Why do we forget things we were just thinking about? —Electronic' scalp tattoos could be next big thing in brain monitoring —'Hyper-synchronized' brain waves may explain why different psychedelics have similar effects, rat study reveals Andrillon and Demertzi suggested mind blanking may act as a mini-reset while we're awake. Demertzi said it's like "taking five to steam off" or "to cool your head." Early studies in Demertzi's lab suggest sleep-deprived people report more mind blanks, adding support to this idea. Both researchers stressed that this state is likely a way for the brain to maintain itself, though "it's not ideal for performance," Andrillon said. Andrillon believes it's possible but unlikely that there are people who have never experienced mind blanking. Detecting a mind blank can be a challenge. "It can require being interrupted," Andrillon said, "to realize, 'OK, actually, there was no content.'"
Washington Post
10 hours ago
- Washington Post
Dolphins in the Potomac River? There are a lot more than you think.
REEDVILLE, Va. — Aboard a small motorboat, the trio of researchers navigated the waters of Chesapeake Bay. It was two hours into their trip, and there was no sign of what they'd come looking for. They watched and waited, at one point plucking a plastic bottle from the water. The researchers, based out of Georgetown University, were accustomed to long stretches with nothing but birds and fishing boats as far as the eye could see.
