Non-disjunction means that chromosomes:

• A. Do not cross over during synapsis.
• B. Do not replicate during interphase.
• C. Have serious mutations.
• D. Do not separate correctly from one another during anaphase.

Answer: (D)

Verified step by step guidance

1. Understand the concept of non-disjunction: Non-disjunction is an error in cell division where chromosomes fail to separate properly during anaphase, leading to an abnormal number of chromosomes in the daughter cells.
2. Review the process of meiosis and mitosis: During anaphase of both meiosis and mitosis, chromosomes are supposed to separate and move to opposite poles of the cell. Non-disjunction occurs when this separation does not happen correctly.
3. Differentiate between the phases of cell division: Synapsis and crossing over occur during prophase I of meiosis, while replication occurs during interphase. Non-disjunction specifically refers to errors during anaphase.
4. Consider the consequences of non-disjunction: This can lead to conditions such as Down syndrome, where there is an extra chromosome, or Turner syndrome, where there is a missing chromosome.
5. Identify the correct statement: Among the given options, the correct description of non-disjunction is that chromosomes do not separate correctly from one another during anaphase.