Question

a chromosome is made up of two ______ attached at the centromere.
a genes
b chromatids
c spindles
d centrosomes

Explanation:

• Genes: Genes are segments of DNA that carry genetic information. They are not the structural components that make up a chromosome in the way described in the question.
• Chromatids: Before cell division, a chromosome replicates. Each chromosome then consists of two sister chromatids attached at the centromere. This matches the description in the question.
• Spindles: Spindle fibers are involved in the movement of chromosomes during cell division (e.g., mitosis or meiosis). They are not part of the chromosome's structure.
• Centrosomes: Centrosomes are organelles that organize the spindle fibers during cell division. They are not part of the chromosome's structure.

Answer:

B. chromatids