Autosomal and X-linked are two types of inheritance patterns that describe the inheritance of a particular genetic trait from one generation to the next.
The main difference between autosomal and X-linked is that autosomal inheritance is the inheritance of traits that are determined by the genes in the autosome whereas X-linked inheritance is the inheritance of traits determined by the genes in one of the sex chromosomes.
Generally, genes come in pairs, each inherited from one parent. Alleles are the variant forms of genes. The dominant alleles prevail over the recessive alleles. Autosomal inheritance refers to a pattern of inheritance in which the transmission of traits depends on the genes in the autosome. The two types of autosomal inheritance are autosomal dominant and autosomal recessive. The presence of a single copy of a mutated gene or the inheritance of a diseased allele from an affected parent is sufficient for a particular individual to be affected by the autosomal dominant traits.
Since the autosomal dominant traits are inherited from parents to the offspring, the autosomal inheritance is also called vertical inheritance. Both male and female offspring have an equal probability of inheriting autosomal dominant traits. Male-to-male transmission can also be observed in autosomal dominant inheritance since a single mutated allele is sufficient for the expression of the trait.
Huntington disease, Marfan syndrome, and myotonic muscular dystrophy are examples of autosomal dominant inheritance. The autosomal dominant inheritance is shown in figure 1. Figure 1: Autosomal Dominant Inheritance. Both copies of genes are mutated in autosomal recessive inheritance.
Each mutated gene can be inherited from a parent who serves as the carrier for the trait. Cystic fibrosis and sickle cell anemia are two examples of autosomal recessive inheritance. X-linked inheritance refers to a pattern of inheritance in which the transmission of traits depends on the genes in the sex chromosomes.
The two types of X-linked inheritance are X-linked dominant inheritance and X-linked recessive inheritance. Because females have two X chromosomes, they have two alleles for any X-linked trait. Females can have one X chromosome with the colorblind gene and one X chromosome with a normal gene for color vision.
Since colorblindness is recessive, the dominant normal gene will mask the recessive colorblind gene. Females with one colorblindness allele and one normal allele are referred to as carriers. They carry the allele but do not express it. Females must inherit two copies of the recessive allele to express an X-linked recessive trait. This explains why X-linked recessive traits are less common in females than males and why they show a different pattern of inheritance than autosomal traits.
Another example of a recessive X-linked Mendelian trait is hemophilia. This is a disorder characterized by the inability of blood to clot normally. England's Queen Victoria, pictured below, was a carrier of the disorder. Two of Queen Victoria's five daughters inherited the hemophilia allele from their mother and were carriers. When they married royalty in other European countries, they spread the allele across Europe, including the royal families of Spain, Germany, and Russia.
Victoria's son Prince Leopold also inherited the hemophilia allele from his mother and actually suffered from the disease. For these reasons, hemophilia was once popularly called "the royal disease.
Are you color blind or think you might be? If you inherited this X-linked recessive disorder, a world without clear differences between certain colors seems normal to you. It's all you have ever known. That's why some people who are color blind are not even aware of it. Simple tests have been devised to determine whether a person is color blind and the degree of this visual deficit.
An example of such a test is pictured below. What do you see when you look at this circle? Can you clearly perceive the number 74? If so, you probably have normal red-green color vision. If you cannot see the number, you may have red-green color blindness.
Being color blind may cause a number of problems. These may range from minor frustrations to outright dangers. For example:. Being aware of conditions such as colorblindness is also important for anyone creating content online. Developing webpages that are legible to all users is an important skill for a variety of jobs.
You can use online tools such as the Toptal Color Blind Filter to ensure that the content you create is usable by all of your customers. Dimples This person is exhibiting a genetic trait — the dimples in their cheeks when they smiles.
What Is Simple Inheritance? Autosomal traits are controlled by genes on one of the 22 pairs of human autosomes. Autosomes are all the chromosomes except the X or Y chromosome, and they do not differ between males and females, so autosomal traits are inherited in the same way regardless of the sex of the parent or offspring. Traits controlled by genes on the sex chromosomes are called sex-linked traits. Because of the small size of the Y chromosome, most sex-linked traits are controlled by genes on the X chromosome.
These traits are called X-linked traits. Single-gene X-linked traits have a different pattern of inheritance than single-gene autosomal traits because males have just one X chromosome. Males always inherit their X chromosome from their mother, and they pass on their X chromosome to all of their daughters but none of their sons.
Studying Inheritance Patterns There are two very useful tools for studying how traits are passed from one generation to the next. Pedigree The charts below are called pedigrees. In the pedigrees below: affected individuals are shown in red, unaffected individuals are shown in blue males are shown as squares, females are shown as circles The top row of a pedigree is the original couple. Two individuals who are connected by a horizontal line are breeding pairs.
The children of the couple are connected to them by vertical lines. The next row of the pedigree shows the couple's children, as well as the partners of the children. And, the third row of the pedigree shows the next generation the grandchildren of the couple at the top of the pedigree. Larger pedigrees can have more rows showing additional generations.
Punnett Square A Punnett square is a chart that allows you to easily determine the expected ratios of possible genotypes in the offspring of two parents. Predicting Genotypes and phenotype with Punnett Squares Mendel developed the law of segregation by following only a single characteristic, such as pod color, in his pea plants.
To develop a Punnett square, possible combinations of alleles in a gamete are placed on the top and left side of a square. Dihybrid cross For a monohybrid cross, we are only looking at a single gene.
Consider this cross This cross focuses on two traits in peas. The trait for yellow peas Y is dominant to the trait for green peas y. The trait for round peas R is dominant to the trait for wrinkled peas r.
A gamete that gets the Y allele: can either get the R allele and be YR or it can get the r allele and be Yr A gamete that gets the y allele: can either get the R allele and be yR or it can get the r allele and be yr A plant that is YyRr will produce 4 different gametes: YR, Yr, yR, yr.
Autosomal single-gene Traits in Humans Single-gene autosomal traits include widow's peak and freckles, both of which are illustrated below. Sex inheritance What determines if a baby is a male or female? The X and Y chromosomes determine male or female sexual development Males produce haploid gametes sperm that are either 23,X or 23,Y.
Females produce haploid gametes eggs that are 23,X. Daughters inherit an X chromosome from their mother and an X chromosome from their father. Sons inherit an X chromosome from their mother and a Y chromosome from their father paternal chromosomes indicated in blue, maternal chromosomes indicated in green. Color blindness is an X-linked recessive trait. A carrier mother and unaffected father can produce unaffected sons and daughters, carrier daughters, and colorblind sons.
Feature: My Human Body Are you color blind or think you might be? For example: If you are color blind, it may be difficult to color-coordinate clothing and furnishings. How many autosomes do human cells contain? How many autosomes are in a karyotype? How do autosomal traits differ from sex-linked traits? What is hemizygous? What are common mistakes students make with sex linkage? What are some examples of sex linkage? What is the main reason that gender-linked disorders are most often observed in males?
What is an example of linkage organism, chromosome number, genes?
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