* Allele: An allele is a specific version of a gene. For example, there are alleles for different hair colors, eye colors, and even thumb traits.
* Dominant: A dominant allele is one that will be expressed even if only one copy is present. It "overrides" the recessive allele.
* Recessive: A recessive allele is only expressed if two copies of it are present. If there's a dominant allele around, the recessive one won't show up.
* Homozygous: A homozygous individual has two identical alleles for a trait. This could be two dominant alleles or two recessive alleles.
* Heterozygous: A heterozygous individual has two different alleles for a trait. One will be dominant, and the other will be recessive.
Now, let's talk about thumbs!
One common thumb trait is the ability to bend the thumb back at a 45-degree angle, which is known as the "hitchhiker's thumb."
* Dominant Allele: The allele for having a hitchhiker's thumb is dominant. We'll represent it with the letter "H".
* Recessive Allele: The allele for not having a hitchhiker's thumb is recessive. We'll represent it with the letter "h".
Possible Genotypes and Phenotypes:
* HH (Homozygous Dominant): This individual will have a hitchhiker's thumb because they have two dominant alleles.
* Hh (Heterozygous): This individual will also have a hitchhiker's thumb because the dominant "H" allele will override the recessive "h" allele.
* hh (Homozygous Recessive): This individual will not have a hitchhiker's thumb because they have two copies of the recessive allele.
In short: Your thumb type is determined by the specific combination of alleles (H or h) you inherit from your parents.
