* Alleles: Alleles are different versions of the same gene. For example, there's an allele for curly hair and an allele for straight hair.
* Dominant and Recessive: Some alleles are dominant, meaning they express their trait even if only one copy is present. Other alleles are recessive, meaning they only express their trait if two copies are present.
* Curly Hair: The allele for curly hair is typically dominant.
* Straight Hair: The allele for straight hair is typically recessive.
Here's why a person with one curly hair allele and one straight hair allele has curly hair:
* Dominant Expression: The curly hair allele is dominant. This means even though the person has one straight hair allele, the curly hair allele "overrides" it, resulting in curly hair.
It's like a tug-of-war:
* The curly hair allele is strong (dominant).
* The straight hair allele is weaker (recessive).
* The curly hair allele wins the tug-of-war, leading to curly hair.
Important Note: There is variation in how curly hair alleles express themselves. Some people with one curly hair allele may have wavy hair, while others have tightly curled hair. This can depend on other genes that also influence hair texture.