Question

this chromosome has two chromatids, joined at the centromere. what process led to the formation of the two chromatids?
the two chromatids were formed by duplication of a chromosome.
the two chromatids were formed by synapsis and the formation of a synaptonemal complex.
the two chromatids were formed by fertilization, bringing together maternal and paternal chromatids.
check answer
thats incorrect.
you are confusing two concepts. dna replication and chromosome duplication produce a chromosome

Explanation:

To determine the correct process, we analyze each option:

• Option 1: During the S - phase of the cell cycle, DNA replication occurs, which leads to the duplication of a chromosome. Each duplicated chromosome consists of two sister chromatids joined at the centromere. This is the correct process for the formation of two chromatids in a single chromosome.
• Option 2: Synapsis and the formation of the synaptonemal complex occur during meiosis I, where homologous chromosomes pair up. This process is related to the pairing of different chromosomes, not the formation of chromatids within a single chromosome.
• Option 3: Fertilization is the process of combining the sperm and egg nuclei, which brings together maternal and paternal chromosomes (not chromatids within a single chromosome). It does not lead to the formation of chromatids in a single chromosome.

Answer:

The two chromatids were formed by duplication of a chromosome.