Sister chromatids - two copies of the same DNA joined at the centromere.
Double helices .
One can find information about alpha helices in your local library.You could find about all other helices in that category and how they are used in life.
The plural of helix is helices.
helix
Double helices .
-Two helices
Alpha helices
Your sister's husband is called your brother- in-law.
Usually, The oldest sister is called "eldest" and the youngest sister is called "youngest" or "smallest".
Alpha helices
The question should be "what do alpha helices and beta sheets create?" They form the tertiary structure of proteins.