Question

what are a & b called, and what is true about the dna found making up each?

Explanation:

In the context of chromosomes, A and B (the two parts of the X - shaped chromosome) are called sister chromatids. Sister chromatids are formed during DNA replication. The DNA in each sister chromatid is identical because they are formed by the replication of a single DNA molecule. This means that they carry the same genetic information, which is important for processes like cell division (e.g., mitosis and meiosis) where the genetic material needs to be accurately distributed to daughter cells.

Answer:

A and B are called sister chromatids. The DNA in each sister chromatid is identical (as they result from the replication of the same original DNA molecule, carrying the same genetic information).