Non-Mendelian Genetics - Video Tutorials & Practice Problems
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1
concept
Polygenic Inheritance
Video duration:
2m
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Video transcript
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 gonna 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 so 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 polygenic trait is human height, which is controlled by well over a 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 1 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 pleiotropie in our next video. So I'll see you all there.
2
Problem
Problem
Which of the following phenotypes is an example of polygenic inheritance?
A
White or purple flower color in pea plants.
B
Yellow or green pea color in pea plants.
C
The ABO blood groups in humans.
D
Skin pigmentation in humans.
3
concept
Pleiotropy
Video duration:
2m
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Video transcript
So now that we've introduced polygenic inheritance in our last lesson video, in this video we're going to introduce pleiotropy. And so pleiotropy is practically the opposite of polygenic, and that's because polygenic means multiple genes affecting one trait. But pleiotropy is when a single gene has effects on multiple different phenotypic traits. And so if we take a look at our image down below over here on the left hand side, we're showing you a representation of pleiotropy. And again pleiotropy is when just one single gene has impacts or effects on multiple different traits. Trait a, b, c, and d. And so again pleiotropy is one gene affecting many traits. And a classic example of pleiotropy is Marfan syndrome, which 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. And so some Marfan syndrome phenotypes include having a tall and slender body, long arms legs and fingers, curved spine, crooked or crowded teeth, heart disease and heart murmurs, and eye conditions or vision loss. And so 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 seemingly might be unrelated but they are all traced back to this one particular gene. And so all of these different traits that you see here are all impacted by just one gene. And so that is the idea of pleiotropy. And so this here concludes our introduction to pleiotropy and we'll be able to get some practice applying these these concepts as we move forward. So I'll see you all in our next video.
4
Problem
Problem
A pleiotropic genetic disorder typically has what characteristics?
A
A single gene is mutated resulting in the change of one phenotypic trait.
B
A single gene is mutated resulting in the change of many phenotypic traits.
C
Many genes are mutated resulting in the change of one phenotypic trait.
D
Many genes are mutated resulting in the change of many phenotypic traits.
5
concept
Multifactorial Characters
Video duration:
1m
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Video transcript
In this video, we're going to introduce multifactorial characters. And so 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. And so in our example down 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. And so 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. And so 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. And so here what you can see is that multifactorial characters are going to be influenced by many types of factors. Genetic factors but also environmental factors as well. And so 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.
6
Problem
Problem
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
The knowledge that multiple alleles are involved.
B
The allele for blue hydrangea is completely dominant over the allele for pink hydrangea.
C
The alleles are codominant.
D
Environmental factors such as soil pH affect the phenotype of flower color.
7
Problem
Problem
A phenotype is controlled by gene A and gene B. Gene B controls the expression of gene A. This is an example of _____.