Question

what key events happen during crossing - over that lead to gene mixing? (select the two correct answers.) (1 point) sister parts separating from each other. dna segments being swapped between chromosomes. the cells dna being copied before division. chromosomes lining up in a single file line. matching chromosomes pairing closely together.

Explanation:

1. Analyze each option:

• "Sister parts separating from each other" is about sister chromatids separating in anaphase, not crossing - over.
• "DNA segments being swapped between chromosomes": During crossing - over, homologous chromosomes exchange DNA segments, which leads to gene mixing.
• "The cell's DNA being copied before division" is DNA replication, not related to crossing - over.
• "Chromosomes lining up in a single file line" is about chromosomes in mitosis or meiosis II alignment, not crossing - over.
• "Matching chromosomes pairing closely together": Homologous chromosomes (matching chromosomes) pair up (synapsis) during prophase I of meiosis, and this is a prerequisite for crossing - over to occur, and the pairing allows for the subsequent DNA segment swapping.

1. So the two correct options are the ones related to the key events of crossing - over: DNA segments being swapped between chromosomes and matching chromosomes pairing closely together.

Answer:

B. DNA segments being swapped between chromosomes, E. Matching chromosomes pairing closely together