13. In a developing human embryo, the hands and feet resemble mittens, with cells and tissues present between the fingers and toes. When a baby is born, these cells are not present, resulting in distinct fingers and toes. In the development of fingers and toes these cells were lost by (A) cell division. (B) cell connections. (C) cell morphology. (D) apoptosis.

15. Why is there a need to produce Okazaki fragments on the lagging strand, but not on the leading strand of DNA? (A) The two parental strands of DNA are antiparallel and DNA polymerase makes DNA in the 5′ to 3′ direction only. (B) It is substantially more efficient to make several shorter strands rather than one longer strand of DNA. (C) There is not enough cellular DNA ligase for bonding Okazaki fragments together if they were produced from both parental strands. (D) By having one leading strand and one lagging strand the cell can limit the amount of DNA polymerase used for chromosomal replication.

相關試題

相關試卷