Which of the following statements about crossing over is true?
1. it occurs only in males.
2. it occurs only in some chromosomes.
3. it occurs only between genes that are heterozygous.
4. it results in reduced genetic variation among meiotic products.
5. none of the answers are correct.

Why can cancer in the lymph nodes (lymphoma) be particularly dangerous? a. the lymph node's ability to produce cancer-fighting lymphocytes would be compromised. b. the lymph node's ability to produce cancer-fighting lymph would be compromised. c. the lymph nodes produce lymph, which nourishes growing cancer cells. d. the lymph nodes produce chyle, which nourishes growing cancer cells.