Understanding Alleles and Traits

Alleles are different versions of a gene that happen because of changes, called mutations. They are found in the same spot on a chromosome.

Every person gets two alleles for each gene, one from their mom and one from their dad. How these alleles work together helps decide which traits get passed down, mainly grouped into two types: dominant and recessive traits.

What are Dominant Traits?

• Definition: A dominant allele is strong enough to hide the effect of another allele.
• Expression: If someone has at least one dominant allele (like AA or Aa), the dominant trait shows up.
• Statistics: Usually, about 75% of the children from a cross with a dominant trait will show that trait if one parent has two dominant alleles and the other has two recessive alleles.

What are Recessive Traits?

• Definition: A recessive allele is one that gets hidden when there is a dominant allele present.
• Expression: For a recessive trait to be seen, a person must have two recessive alleles (like aa).
• Statistics: Roughly 25% of the children will show the recessive trait when both parents have one dominant and one recessive allele (like Aa x Aa).

What are Punnett Squares?

To help predict how traits are passed down, scientists often use something called Punnett squares. Here’s a simple example:

• Alleles: A (dominant) and a (recessive)
• Cross: When you cross Aa with Aa, you get a ratio of 1:2:1 for the different genotypes (AA, Aa, aa) and a ratio of 3:1 for the traits seen (dominant:recessive).

In Summary

Alleles are very important for figuring out how traits get passed down from parents to children. They affect what traits we see based on whether they are dominant or recessive. By understanding these patterns, we can make guesses about the traits that future generations might have.