Polygenic Inheritance Key Takeaways
- In polygenic inheritance, traits are determined by multiple genes, or polygenes.
- Polygenic traits may express several different phenotypes, or displayed characteristics.
- Polygenic inheritance is a type of incomplete dominance inheritance, where the expressed phenotypes are a mixture of inherited traits.
What is different between a multiple trait and a polygenic?
What are the Similarities Between Multifactorial and Polygenic Traits?
- Multifactorial traits are polygenic traits that are strongly influenced by the environment.
- They are controlled by many genes/alleles.
- They are exceptions of Mendelian inheritance.
- Many human disorders are multifactorial or polygenic diseases.
- Multifactorial and polygenic diseases are very complex to resolve.
How many genes influence a polygenetic trait?
Traits controlled by two or more genes are said to be polygenic traits. Many human traits such as height, skin color, hair color, etc. are results of polygenic traits. The image below shows the varying scale of human skin color. Scientists believe that at least three different genes code for skin color. The allele for dark skin, D, is dominant over the allele for light skin, d.
Why are polygenic traits more influenced by the environment?
The phenotype is a mixture of the phenotypes inherited from the parent alleles. Environmental factors can also influence polygenic traits. Polygenic traits tend to have a bell-shaped distribution in a population. Most individuals inherit various combinations of dominant and recessive alleles. These individuals fall in the middle range of the curve, which represents the average range for a particular trait.
Are polygenic traits controlled by no more than three alleles?
Polygenic inheritance defines as more than two alleles (maybe a group of alleles) which control a single characteristic. A single trait that controlled by multiple genes or alleles, is said to be a polygenic inheritance.
How polygenic traits are determined?
In polygenic inheritance, traits are determined by multiple genes, or polygenes. Polygenic traits may express several different phenotypes, or displayed characteristics. Polygenic inheritance is a type of incomplete dominance inheritance, where the expressed phenotypes are a mixture of inherited traits.
What determines a polygenic trait phenotype?
While Mendelian traits tend to be influenced by a single gene, the vast majority of human phenotypes are polygenic traits. The term polygenic means “many genes.” Therefore, a polygenic trait is influenced by many genes that work together to produce the phenotype.
What is polygenic determination?
In polygenic sex determination. (PSD), multiple, independently. segregating sex 'switch' loci or. alleles determine sex within a. species.
How are polygenic traits inherited?
Inheritance. Polygenic inheritance occurs when one characteristic is controlled by two or more genes. Often the genes are large in quantity but small in effect. Examples of human polygenic inheritance are height, skin color, eye color and weight.
Which two factors could affect the expression of polygenic traits?
Nature and nurture both affect phenotypic expression. Intelligence, depression, height, skin color, schizophrenia are some of the human characters that are affected by the environment. A medical example of the effect of environmental factors on polygenic inheritance is the hereditary disorder phenylketonuria.
Why are polygenic traits expressed through quantitative variation?
Explain why polygenic traits are expressed through quantitative variation, using skin color as an example. If there are more alleles present for darker skin tone, then the offspring will have darker skin pigment than the parents may have.
Which outcome could help you identify a trait whose expression is determined by the effects of two or more genes polygenic inheritance )?
Which outcome could help you identify a trait whose expression is determined by the effects of two or more genes (polygenic inheritance)? The trait varies along a continuum in the population.
How are polygenic traits different from traits that only require 2 genes?
8) How are polygenic traits different from traits that only require 2 genes? The polygenic traits have a wide variation in each trait. 9) Why do you think that some children are taller than their parents? The children can have more tall genes than either parent.
What kinds of environmental factors influence the expression of traits?
Environmental factors such as diet, temperature, oxygen levels, humidity, light cycles, and the presence of mutagens can all impact which of an animal's genes are expressed, which ultimately affects the animal's phenotype.
What factors can affect gene expression?
Gene expression can be altered by environmental factors such as food, drugs or exposure to toxins, according to Duke Magazine. These changes can range from small to so significant that certain genes in our system can be turned off or on when they are supposed to be the opposite way.
What is a polygenic trait quizlet?
a trait that is controlled by several pairs of genes; different combinations of all the genes contribute to the trait in varying degrees.
Which of the following phenotypes is an example of polygenic inheritance?
So, the correct answer is 'Skin colour in humans'.
Why might polygenic traits vary more in phenotype than do single gene traits?
Why might polygenic traits vary more in phenotype than do single gene traits? Polygenic traits are controlled by two or more genes, so there are more combination of alleles leading to multiple phenotypes.
What is polygenic inheritance and how does it explain behavioral phenotypes?
A polygenic trait is a trait in which the phenotype is controlled by more than one gene. Phenotype is the physical or behavioral traits of an organism, whereas their genotype is the genetic makeup and specific combination of genes and alleles present.
What is a polygenic trait quizlet?
a trait that is controlled by several pairs of genes; different combinations of all the genes contribute to the trait in varying degrees.
What is a polygenic trait?
Polygenic Trait. Polygenic Trait. =. A polygenic trait is one whose phenotype is influenced by more than one gene. Traits that display a continuous distribution, such as height or skin color, are polygenic. The inheritance of polygenic traits does not show the phenotypic ratios characteristic of Mendelian inheritance, ...
Why are people not the same height as their parents?
Height in humans is very strongly genetically controlled, but there are many, many different genes that control height. And this is why people are not the exact height of their parents. Skin color is another trait that is very obvious in humans that is controlled by many, many different genes. And this is why you get differences between parents ...
Is polygenic inheritance phenotypic?
The inheritance of polygenic traits does not show the phenotypic ratios characteristic of Mendelian inheritance, though each of the genes contributing to the trait is inherited as described by Gregor Mendel. Many polygenic traits are also influenced by the environment and are called multifactorial.
Is a polygenic trait a Mendelian trait?
Polygenic traits are quite different from the classical Mendelian trait in where we see that one gene controls one characteristic or one phenotype. Surprisingly, most traits in humans, and in fact most traits in most organisms, are polygenic. Mendelian traits, although we spend a lot of time talking about them, are really the exception.
What is polygenic traits?
Polygenic Traits Definition. Polygenic traits are traits that are controlled by multiple genes instead of just one. The genes that control them may be located near each other or even on separate chromosomes. Because multiple genes are involved, polygenic traits do not follow Mendel’s pattern of inheritance. Instead of being measured discretely, ...
Why are polygenic traits not inherited?
Because multiple genes are involved, polygenic traits do not follow Mendel’s pattern of inheritance. Instead of being measured discretely, they are often represented as a range of continuous variation. Some examples of polygenic traits are height, skin color, eye color, and hair color.
What are the two traits that are represented by only one gene?
This is because each trait was represented by only one gene which had two alleles: dominant and recessive. If a plant had two dominant alleles, or one dominant and one recessive allele, the flowers were purple, while if it had two recessive alleles, the flowers were white. Polygenic traits also have dominant and recessive alleles, ...
What is the basic unit of heredity?
Gene – The basic unit of heredity; made up of DNA, it is transferred by parent to offspring and codes for a specific part of the offspring’s phenotype. Allele – A certain variant of a gene . Melanin – A pigment in skin, hair, and eyes that affects its color. Phenotype – Any part of an organism’s physical appearance.
How many genes are involved in height?
Height. Human height is controlled by many genes; in fact, there are over 400 genes related to height, and all of these genes interact to make up a person’s phenotype. This is a very large number, but it makes sense because height is a compilation of the lengths of many different body parts, such as leg bones, the torso, and even the neck. ...
Why do people have green eyes?
Green eyes are caused by multiple factors; they are the result of a light brown iris combined with a blue tone given by light scattering.
How does the eye color of a person determine the color of their eyes?
A person’s eye color is determined by the pigmentation of their irises, but also by the way the cells in their irises scatter light.
How are polygenic traits determined?
Polygenic traits are determined by the interactions between several different genes, which display incomplete dominance. 2. How many different allele combinations can possibly be produced from two parents that are heterozygous for a polygenic trait controlled by three different genes with two allele pairs? A. 5. B. 7.
What are the physical traits that are controlled by polygenic inheritance?
Because of the inheritance mode patterns, the physical traits that are controlled by polygenic inheritance, such as hair color, height and skin color, as well as the non-visible traits such as blood pressure, intelligence, autism and longevity, occur on a continuous gradient, with many variations of quantifiable increments.
What is the probability of the second lightest skin tones?
As the number of contributing alleles changes within the allele combinations, the units of melanin pigment increases and decreases; the probability of the second lightest or darkest skin tones (1 or 5) is 6/64, the third lightest or darkest skin tones (2 or 4), is 15/64 and an entirely intermediate skin tone (3) is the most common at 20/64.
What is additive effect in polygenic inheritance?
It is important to remember here that in polygenic inheritance, alleles do not display dominance over others, rather, each contributing allele gives an additive effect rather than a masking effect, and so the way that the alleles interact is different to those in Mendelian genetics. The additive effect means that each contributing allele produces ...
What is polygenic inheritance?
Polygenic inheritance, also known as quantitative inheritance, refers to a single inherited phenotypic trait that is controlled by two or more different genes. In a system which differs from Mendelian Genetics, where monogenic traits are determined by the different alleles of a single gene, ...
What is the pigment that controls skin color?
The pigment melanin is responsible for dark coloration in the skin and there are at least three genes, which control for human skin color. Using a hypothetical example where the production of melanin is controlled by contributing alleles (denoted here as A, B and C), resulting in dark skin color, and therefore light skin color is produced by non contributing alleles (denoted here as a, b and c), it is possible to see how the spectrum of different skin colors can result in the offspring.
How many genes are involved in human height?
Human Height. Human height is an extremely complex inheritance pattern as there are over 400 genes controlling for it, it is therefore extremely difficult to predict the height that an offspring will be; two short parents may produce a tall child, whereas two tall parents can produce a short child and parents with completely different heights may ...
What is a Polygenic Trait?
A polygenic trait is a trait in which the phenotype is controlled by more than one gene. Phenotype is the physical or behavioral traits of an organism, whereas their genotype is the genetic makeup and specific combination of genes and alleles present. Polygenic characteristics are both:
Genetic Inheritance
Genetic inheritance is the way that people inherit their traits. All diploid organisms inherit two sets of chromosomes, one set from the maternal parent and one set from the paternal parent. In humans, each person gets 23 chromosomes from their mom and 23 chromosomes from their dad.
Monogenic Traits and Mendelian Inheritance
Monogenetic traits are traits that are controlled by a single gene. These genes are typically inherited with two alleles, one which is dominant and masks the other, called the recessive allele. This type of inheritance pattern is called Mendelian Inheritance after the Austrian monk Gregor Mendel.
Answer
Polygenic traits are quantitative because their phenotype expression depends on several different alleles found on different chromosomes.
Answer
If there are more alleles present for darker skin tone, then the offspring will have darker skin pigment than the parents may have.
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