Morton's Toe: Dominant or Recessive?

Updated on February 13, 2018
Source

My second toe is longer than my first toe. As a young child, I thought this was the norm, but I gradually became aware that for a great number of people the second toe is of equal length or shorter than the first toe. I set out to do some research to find out why I had a freakishly long second toe, also known as a Celtic toe, or, more commonly, Morton’s toe.

I learned that Morton’s toe is hereditary. Furthermore, it appears to be a dominant trait, according to McKusick.

Kaplan (1964) claimed that the relative length of the hallux (footnote) and second toe is simply inherited, with the long hallux being recessive. In Cleveland Caucasoids, the frequency of the dominant and recessive phenotypes was 24 percent and 76 percent, respectively. Usually, the first toe is longest, although in the Ainu the second toe is said to be longest in 90 percent of persons. In Sweden, Romanus (1949) found the second toe to be longest in 2.95 percent of 8,141 men. Romanus thought the long second toe to be dominant with reduced penetrance. Beers and Clark (1942) described a family in which the long second toe occurred in 10 persons in 3 generations (McKusick, 1998).

Although the Mckusick information was quite convincing, additional information was needed to provide further support for the claim that Morton’s toe is, indeed, a dominant trait. The results of that accumulative research supported nothing, as Morton’s toe is said to be both dominant and recessive, depending on the source. One reason for there being no definitive answer is that Morton’s toe, like several other traits, was previously believed to be Mendelian, but is now believed to be based on more complex genetic models. Therefore, there appears to be conflicting beliefs as to whether this phenomenon is the result of a dominant or recessive gene trait. So, the representation of Morton’s toe as a dominant trait in this essay is simply arbitrary.

Punnett Square

The Punnett square is a chart used by geneticists to show all possible allelic combinations of gametes in a cross of parents with known genotypes. Predicted offspring genotype frequencies can be calculated by tallying the allelic combinations in the P-square. As neither of my children share this trait, I will use a Punnet square to illustrate how they seem to have inherited their father’s toes, or, more accurately, not mine. For the purpose of this demonstration, Morton’s toe is assumed to be a dominant trait.

This Punnet Square represents Parental Genotype Mm X Parental Genotype mm.

 
M
m
m
Mm
mm
m
Mm
mm


The resulting genotype frequencies are:

  • mm: 2 (50.0%)
  • Mm: 2 (50.0%)

All four possibilities of offspring will not have Morton’s toe, but will carry the gene for it. There are actually two offspring, neither of whom have Morton’s toe. But since they carry the recessive gene, one of the offspring could pass it along to one of her own offspring.

Punnett squares can be used to calculate the probability of any genetic trait appearing in offspring. These include:

Dominant Traits
Recessive Traits
Brown eyes
Grey eyes, green eyes, blue eyes
Dimples
No dimples
Unattached earlobes
Attached earlobes
Freckles
No freckles
Broad lips
Thin lips
Farsightedness
Normal vision
Normal vision
Nearsightedness
Normal vision
Color blindness

Of course, this is just a small representation of the endless possibilities of traits one might inherit, but it’s enough to give a basic idea of how the principle works. Note that in the table above, the farsightedness trait is dominant over the recessive trait for normal vision, while normal vision trait is dominant over nearsightedness and color blindness. This indicates that a trait might be either dominant or recessive, depending on what it’s being compared to.

I would like to conclude by stating that although Mendel was able to found modern basic genetics involving single gene traits, recent studies have found a number of variables that cannot be explained by Mendelian laws. For instance, some complex traits are determined by multiple genes and environmental factors, and therefore do not conform to simple Mendelian patterns. Such complex non-Mendelian disorders include heart disease, cancer, diabetes, and more. Fortunately, these disorders are becoming more accessible with recent advances in genomics. Once again, science will prevail.

Sources

Gregor Mendel (1822-1884) was the founder of modern genetics. http://anthro.palomar.edu/mendel/mendel_1.htm

Dominant and Recessive Characteristics. http://www.blinn.edu/socialscience/ldthomas/feldman/handouts/0203hand.htm

© 2010 DebbieSolum

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    • profile image

      Sophia 

      9 days ago

      If you’re using a normal Punnett square to suggest the traits, then the “Morton’s Toe” trait must be dominant. There is not other more complex way of passing on the trait with a 2x2 Punnett square. It will always either be MM (Morton’s toe), Mm (Morton’s toe masks little m), or mm (not Morton’s toe).

    • Guckenberger profile image

      Alexander James Guckenberger 

      8 months ago from Maryland, United States of America

      The Statue of Liberty has a Morton's toe. ^_^

    • profile image

      Wolf Lawrence 

      16 months ago

      i'm also confused what OP's conclusion is. elsewhere i've read 'dominant'.

    • profile image

      wolf 

      16 months ago

      Morton's Foot is also called Neanderthal Foot and i just read that every neanderthal footprint ever found had the shorter big toe.

    • profile image

      bob 

      2 years ago

      Yes Isaac you are.

      Your parents didn't have the heart to tell you but I never liked you anyway so... Yes!

      Ouu ouu, ahh ahh!

    • profile image

      Isaac McLain 

      3 years ago

      Both of my toes beside my big toe are longer. Im 5 foot 7 with a shoe size of 12 and 19 years old. Am I a monkey?

    • profile image

      Amy Fisher 

      3 years ago

      Speak for yourself. It's not freakish. Seriously, grow up. Only immature people/ kids say those things. Ignorance is not bliss. Bye.

    • profile image

      bob 

      4 years ago

      Mendel was a monk whose work on pea plants helped found modern genetics. You refer to him as Mendelian here; the science is referred to as Mendelian genetics, but the man was named Mendel.

    • profile image

      Charlie 

      6 years ago

      Actually since Morton's you're was, there was a 50% chance of you're kids having it since the dominant trait would have won out.

    • profile image

      Lianna HIll 

      7 years ago

      Okay, so from this article I was left confused is this trait dominant or recessive or co-dominant or incomplete dominance???? I need this information for a genetics project so feel free to email me at liannanhill@gmail.com

      Thanks a bunch!

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