Blue Eyes, Recessive is Absence of Melanin in Iris

10 Human Genetic Traits of Simple Inheritance 

Which Do You Have?

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The most fun way to learn a little about genetics is to understand heredity first hand, your own heredity; and you can do that by examining the actual dominant and recessive traits that you possess.

Genes from Mom & Dad Determine Your Traits
You are a diploid organism, meaning that 
Article Summary: Which traits did you inherit from your mother; from your father? Take this simple genetic quiz and learn about the genes that you possess.
10 Human Genetic Traits of Simple Inheritance
4. Bent Little Finger: A dominant allele causes the last joint of the little finger to dramatically bend inward toward the 4th finger. Lay both hands flat on a table relax your muscles, and note whether your have a bent or straight little finger.

Dominant (have it) ___ 
Recessive (don't have it) ___.
Father and son with dominant trait of curved pinkey.
5. Facial Dimples: If you aren't sure if you have them, smile! Dimples are easiest to see when smiling. With dominant phenotype, you may have a dimple only on one side, or on both.

Dominant (have it) __ Recessive (don't have it) ___.
Boy with cleft chin, dimples and brown eyes (melanin), all dominant traits.
Boy with cleft chin, dimples and brown eyes (melanin), 
all dominant traits.





Need Help with Genetics?

SPO offers free PowerPoint lectures, sample test
questions, review questions and assignments on many different science topics. 

Below are links to those that relate to genetics:
1. Mendelian Genetics & Heredity

2. Molecular Genetics: Replication

3. Molecular Genetics: Transcription & Translation
Color Coded Chromosomes, Institute of Human Genetics
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Some Genes Mask the Expression of Other Genes
In some instances, the version of a gene that you get from one parent may block the expression of the version of that same gene you received from the other parent. 
Instructor's Corner
Girl with dimples, cleft chin and blue eyes.
Girl with cleft chin, dimples and blue eyes (no melanin).
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See Page 2 for homework assignment and other free teaching materials on Mendelian Genetics!
Father and son who both have bent little finger. Mother (not pictured) does not have a bent little finger.
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you received one set of genes (called alleles) from your father and the other set of alleles from your mother. 

The combination of these pairs of genes that you've inherited is called your "genotype." The genotype determines the actual traits (called the "phenotype") that you have; such as eye color, nearsightedness, and whether or not you have dimples.


Examples of Simple Inheritance of Traits that Show Complete Dominance
The characteristics listed below are products of simple inheritance. One can either possess the dominant phenotype or the recessive phenotype. All of the following are dominant traits, meaning that if the trait described is present, it is the dominant phenotype. If the trait is absent, the corresponding genotype is recessive.

At the end of the description of each trait, is an area where you can check off whether you are dominant or recessive for that trait. See page 2 of this article for a printable assignment on which you can mark which characteristics you have. Forward this article to family members so they can do the same. Then compare notes. For some traits, you'll be able to trace that inheritance pattern of the associated genes through your family. Have fun!

1. Achoo Syndrome: This dominant trait is also called the photo sneeze reflex. If, when suddenly exposed to light, you sneeze (usually two or three times) you have the genes for achoo syndrome. Next time you go to a movie, exit the dark theater through a door that leads directly outside. It's fun to wait outside and watch the people emerge from the movie. Some will sneeze as soon as they are exposed to light.

Dominant (have it) __ Recessive (don't have it) ___.


2. Chin Cleft: A prominent cleft in the chin is due to the bond structure which underlies the Y-shaped fissure of the chin. Females appear to be less conspicuously affected than males.

Dominant (have it) __ Recessive (don't have it) ___.


​3. Early Onset Myopia (Childhood Nearsightedness): Nearsightedness, or myopia, is a complex trait with at least 4 gene loci involved, however the heritability of myopia is very high and shows a dominant pattern.

Dominant (have it) __ Recessive (don't have it) ___.


Brown eyed son of brown eyed mother and green eyed father.
Blue eyed daughter of brown eyed mother and green eyed father.
=
Brown eyed mother and green eyed father produced one brown eyed child and one blue eyed child.
Brown eyed mother and blue eyed father produced one brown eyed child and one 
blue eyed child. Because this couple was able to produce a blue eyed child, the mother is heterozygous for brown eyes (She has 1 brown and 1 non-brown allele).
It is kind of like the game Rock, Paper, Scissors, but in this case, brown beats non-brown. If you have blue eyes, you had to have inherited a recessive, non-brown eye allele from both parents. 
This is a case of a dominant allele masking the expression of a recessive allele. Recessive alleles are only expressed if you inherit two of them, one from each parent.

For example, if your mother has brown eyes and your father has blue eyes (non-brown), you may have ended up with brown eyes. Your father's blue eyes are a recessive trait, and although you have an allele for blue eyes, the dark eye allele that you received from your mother masks the expression of the blue eye, recessive allele. 
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