What Is an Example of a Gene Trait?

Genes are present in all animals and plants. Chromosomes inside the cells hold strands of genetic information called DNA. DNA is present in matching sets or pairs. Each cell in the human body contains about 25,000 to 35,000 genes.

In humans, a cell nucleus contains 46 individual chromosomes or 23 pairs of chromosomes. Half of these come from the father and the other half from the mother.

Like chromosomes, genes are in pairs. Parents have two copies of each of their genes and pass along just one copy to make up the genes for their children.

When they are lined up by size and in a similar striping pattern, the first 22 pairs are called autosomes (nonsex), and the final pair of chromosomes are called sex chromosomes, X and Y.

• A woman has two X chromosomes (46, XX)
• A man has one X and one Y chromosome (46, XY)

Genes carry the information that determines the characteristic traits (such as hair color and skin color) of a person. These traits are inherited or passed from parents to their children.

The DNA in a gene codes specific instructions to produce proteins required for the development of bones, teeth, hair, earlobes, muscles, and blood.

Most diseases have a genetic component. Disorders in which genes play an important role can be classified as the following:

• Single-gene defects
• Chromosomal disorders
• Multifactorial

Examples of inheritance patterns include the following:

• Autosomal dominant: The genes for a trait or condition are dominant on a nonsex chromosome.
• Autosomal recessive: The genes for a trait or condition are recessive on a nonsex chromosome.
• X-linked dominant: The genes for a trait or condition are dominant on the X-chromosome.
• X-linked recessive: The genes for a trait or condition are recessive on the X-chromosome.
• Y-linked: The genes for a trait or condition are on the Y-chromosome.
• Codominant: Each allele in a gene pair produces combined physical characteristics.

A few examples of gene disorders include the following:

• Single-gene defects
  • Autosomal recessive
    • Adenosine deaminase deficiency 
    • Alpha-1-antitrypsin deficiency
    • Cystic fibrosis
    • Phenylketonuria
    • Sickle cell anemia
  • X-linked recessive
    • Duchenne muscular dystrophy
    • Hemophilia A
  • Autosomal dominant
    • Familial hypercholesterolemia
    • Marfan syndrome
  • X-linked dominant
    • Hypophosphatemic rickets
    • Vitamin D-resistant rickets
• Chromosomal disorders
  • Microdeletion syndrome
  • Down syndrome
  • Klinefelter’s syndrome
  • Turner’s syndrome
• Multifactorial disorders
  • Asthma
  • Cancer
  • Coronary heart disease
  • Diabetes
  • Hypertension
  • Stroke