A single, unreplicated chromosome (without the sister) is called?

A single, unreplicated chromosome (without the sister) is called?

• A. Chromatid
• B. Chromosome
• C. Sister Chromatid
• D. Chromosome Arm

Answer: (A)

Understanding how chromosomes are organized around replication clarifies the terminology. Before DNA replication, the genetic material exists as a single DNA molecule packaged into a chromosome, so this unreplicated form is simply called a chromosome. After replication, the chromosome consists of two identical DNA molecules that form sister chromatids held together at the centromere; each chromatid is one half of the replicated chromosome. A chromosome arm is just a part of a chromosome, not the whole structure. So a single, unreplicated chromosome is called a chromosome.

Understanding how chromosomes are organized around replication clarifies the terminology. Before DNA replication, the genetic material exists as a single DNA molecule packaged into a chromosome, so this unreplicated form is simply called a chromosome. After replication, the chromosome consists of two identical DNA molecules that form sister chromatids held together at the centromere; each chromatid is one half of the replicated chromosome. A chromosome arm is just a part of a chromosome, not the whole structure. So a single, unreplicated chromosome is called a chromosome.