57. Brings in the correct
nucleotides and matches
them up.
58.
59.
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.
