Simple Mendelian Inheritance in Humans

In this simple Mendelian inheritance in humans post we have briefly explained about mendelian inheritance in man, autosomal traits, sex-linked traits. Read to learn more about mendelian inheritance in man!

Red-green colour-blindness is a common inherited trait in humans. About 1 in 10 men have some form of color blindness. However, very few women are color blind. Why?

Mendelian Inheritance in Man

Characteristics encoded within DNA are referred to as genes. Human traits of various kinds can be inherited in multiple ways. Similar to the traits Gregor Mendel studied in pea plants, certain human traits are simple inheritance patterns, and human traits can have more complicated inheritance patterns.

Mendelian inheritance in man is the transmission of traits with a particular gene with two alleles, one which could be dominant over the other. Many human characteristics aren’t caused by just one gene containing two alleles. However, they’re an excellent start to comprehend human heredity. Mendelian traits are passed down through generations contingent on the degree to which autosome genes or the X chromosome determines the traits.

Autosomal Traits

Autosomal traits are controlled by genes on one of the 22 human autosomes. Consider earlobe attachment. A single autosomal gene with two alleles determines whether you have attached earlobes or free-hanging earlobes. The allele for free-hanging earlobes (F) is dominant to the allele for attached earlobes (f). Other single-gene autosomal traits include widow’s peak and hitchhiker’s thumb. The dominant and recessive forms of these traits are shown in Figure below. Which form of these traits do you have? What are your possible genotypes for the traits?

The chart in Figure below is called a pedigree. It shows how the earlobe trait was passed from generation to generation within a family. Pedigrees are useful tools for studying inheritance patterns.

Mendelian Inheritance in Humans

Mendelian Inheritance in Man: Autosomal Traits

Having free-hanging earlobes is an autosomal dominant trait. This figure shows the trait and how it was inherited in a family over three generations. Shading indicates people who have the recessive form of the trait. Look at (or feel) your own earlobes. Which form of the trait do you have? Can you tell which genotype you have?

Other single-gene autosomal traits include widow’s peak and hitchhiker’s thumb. The dominant and recessive forms of these traits are shown in Figure below. Which form of these traits do you have? What are your possible genotypes for the traits? Widow’s peak and hitchhiker’s thumb are dominant traits controlled by a single autosomal gene.

Mendelian Inheritance in Humans 2

Mendelian Inheritance in Man: Autosomal Traits

Sex-Linked Traits

Sex-linked traits, or X-linked traits in the case of the X chromosome, are qualities regulated by genes on the sex chromosomes. The inheritance pattern for single-gene X-linked traits differs from that of single-gene autosomal traits. Because males only have one X chromosome, this is the case. Furthermore, they always acquire their mother’s X chromosome, which they pass on to all of their daughters but none of their sons.

Mendelian Inheritance in Humans

Mendelian Inheritance in Man: Sex-Linked Traits

Sex Chromosome Inheritance. Only X chromosomes are passed down from mothers to their children. Fathers always give their daughters their X chromosome and their sons their Y chromosome. Can you explain why the father always determines the sex of the offspring?

Males have only one allele for any X-linked trait since they only have one X chromosome. As a result, males always display a recessive X-linked allele. Females have two alleles for any X-linked characteristic since they have two X chromosomes. To express the recessive trait, they must inherit two copies of the recessive allele. This explains why females have fewer X-linked recessive characteristics than males. Red-green color blindness is an example of a recessive X-linked trait. This characteristic causes people to be unable to distinguish between the hues red and green. This characteristic is very prevalent in males but relatively rare in females is coded for by more than one recessive gene on the X chromosome.

Mendelian Inheritance in Humans

Mendelian Inheritance in Man: Sex-Linked Traits

Pedigree for Color Blindness. Color blindness is an X-linked recessive trait. Mothers pass the recessive allele for the trait to their sons, who pass it to their daughters.

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