In this video, we're going to talk about some non-Mendelian genetics or genetics that is not described by Gregor Mendel's laws. And we're going to start off by talking about polygenic inheritance. And so it turns out that most inherited traits are actually polygenic. And so what exactly does it mean for traits to be polygenic? Well, polygenic traits, as their name implies with the poly root, which means many, and the genic root here, which of course is referring to genes. These are going to be single phenotypic traits that are affected by multiple genes. And again, you can see that within the root polygenic. Poly meaning many or multiple, and genic of course referring to the genes. And so polygenic traits are single phenotypic traits affected by multiple genes. And so, if we take a look at our image down below over here on the left-hand side, notice we're showing you a representation of a polygenic trait. One single phenotypic trait affected by multiple genes, gene A, gene B, gene C, and gene D over here. And so when you have many genes affecting one trait, that is what's referred to as a polygenic trait. Now, a classic example of a polygenic trait is human height, which is controlled by well over 180 genes. And so when you take a look at this image down below, you can see that we have different human heights, one at 6 feet 5 inches, 6 feet, 5 feet 5 inches, and one at 5 feet. And again, human height is controlled by well over 180 genes. And so, that makes it a polygenic trait since it's a single trait, a single human height is a single trait that's affected by multiple genes. And that, of course, is going to be much more complicated than the simple Mendelian genetics that we've talked about in our previous lesson videos. And so now that we've described polygenic inheritance, we'll be able to compare this to pleiotropy in our next video. So I'll see you all there.
Non-Mendelian Genetics - Online Tutor, Practice Problems & Exam Prep
Polygenic inheritance involves multiple genes influencing a single phenotypic trait, exemplified by human height, which is affected by over 180 genes. In contrast, pleiotropy occurs when a single gene impacts multiple traits, as seen in Marfan syndrome, where one gene mutation affects various body systems. Multifactorial characters are influenced by both genetic and environmental factors, such as the pH of soil affecting hydrangea flower color. Understanding these concepts is crucial for grasping the complexity of genetic traits and their interactions with the environment.
Polygenic Inheritance
Video transcript
Which of the following phenotypes is an example of polygenic inheritance?
Pleiotropy
Video transcript
So now that we've introduced polygenic inheritance in our last lesson video, in this video we're going to introduce pleiotropy. Pleiotropy is practically the opposite of polygenic, and that's because polygenic means multiple genes affecting one trait. However, pleiotropy is when a single gene has effects on multiple different phenotypic traits. If we take a look at our image down below here on the left-hand side, we're showing you a representation of pleiotropy. Pleiotropy is when just one single gene has impacts or effects on multiple different traits, such as traits A, B, C, and D. Pleiotropy is one gene affecting many traits. A classic example of pleiotropy is Marfan syndrome, where a mutation of just one single gene, the FBN1 gene, will limit the body's ability to build connective tissue and lead to a wide variety of phenotypic traits being affected. Some Marfan syndrome phenotypes include having a tall and slender body, long arms, legs, and fingers, a curved spine, crooked or crowded teeth, heart disease and heart murmurs, and eye conditions or vision loss. We have one single gene, this FBN1 gene, which if a mutation occurs there are effects or impacts in the body, the arms, the legs, the fingers, the spine, the teeth, the heart, and the eyes which might seem unrelated but are all traced back to this one particular gene. All of these different traits that you see here are all impacted by just one gene.
This concludes our introduction to pleiotropy and we'll be able to get some practice applying these concepts as we move forward. So, I'll see you all in our next video.
A pleiotropic genetic disorder typically has what characteristics?
Multifactorial Characters
Video transcript
In this video, we're going to introduce multifactorial characters. Multifactorial characters are inherited features or phenotypes that are influenced by many types of factors, and these factors include genetic factors such as alleles, but also environmental factors such as, for example, the temperature or the pH. In our example below, we're going to take a look at the effects of the environment, specifically the pH of the soil on flower color phenotypes of these specific flowers called hydrangea. The hydrangea flower color is impacted by the pH of the soil. Not only is it impacted by genetic factors, but it's also again impacted by environmental factors such as the pH of the soil. When the pH is acidic, these flowers tend to have a bluish type of phenotype. However, when the soil pH is more basic, then the flowers take on a more pinkish type of phenotype. Here, you can see that multifactorial characters are going to be influenced by many types of factors, genetic factors but also environmental factors as well. This here concludes our introduction to multifactorial characters, and we'll be able to get some practice as we move forward throughout our course. So, I'll see you all in our next video.
Hydrangea plants of the same genotype are planted in a large flower garden. Some of the plants produce blue flowers and others pink flowers. This can be best explained by which of the following?
A phenotype is controlled by gene A and gene B. Gene B controls the expression of gene A. This is an example of _____.
Do you want more practice?
More setsYour General Biology tutor
- Is a round yellow pea seed (genotype RrYy) an example of polygenic inheritance? Why or why not
- What factors cause quantitative variation in a trait within a population?
- A quantitative trait . a. may be one that is strongly influenced by the environment; b. vari...
- When graphing the phenotypes of a trait controlled by many genes and the environment, the line showing the fre...
- Skin color in humans is at least partially hereditary; dark-skinned parents tend to have dark-skinned children...