44. It untwists the Double Helix.

57. Brings in the correct nucleotides and matches them up.

60. Mitosis DNA replication occurs during the synthesis phase. In DNA replication helicase untwists the double helix and the leading strand separates from the lagging strand. Then DNA polymerase brings in the correct nucleotides to build the other halves of DNA. Finally it twists back up into a double helix and you have two identical strands of DNA.

61. Why Does DNA Copy? DNA needs to copy so that all of your cells have the same exact copy of DNA and have the right genetic information.

62. Telomeres are the junk ends of DNA. Okazaki fragments are on the lagging strand of DNA. They are placed on the DNA strand in fragments and DNA ligase is the enzyme that stitches them together.

63. Telomerase and Cancer Telomerase is an enzyme that adds more telomeres to the 3’ end of DNA. Cancer cells can produce their own telomerase, so they have enough telomeres to grow indefinitely. Using a substance that prevents the action of telomerase may help fight cancer, but it may also harm our other cells.

64. Transplant Cells Transplant cells die out after a few mitotic divisions and you need to add more. If the cells are transformed with a telomerase gene and a therapeutic gene they should be able to divide forever. There are certain studies to see if it would cause cancer.

65. Cloning When cells are cloned, their telomeres are shorter than normal because they have been deprived of telomerase while they were cultured. This shortens their life spans.

66. Cell Aging A cell’s life span depends on the length of their telomeres. A cell with longer telomeres can undergo mitosis more than on with shorter telomeres can. Certain cells, like cancer cells are able to maintain the length of their telomeres with the help of telomerase. This means that they can divide indefinitely. Certain cells, like cancer cells are able to maintain the length of their telomeres with the help of telomerase. This means that they can divide indefinitely.