2. DNA Replication
DNA replication is the process where a copy of a
DNA strand is made and the genetic information
it contains is duplicated.

3. Step 1
An enzyme known as helicase enters at a
adenine and thymine bond at a point known as
the origin of replication. Helicase unwinds the
double helix as it goes through the DNA strand.
As helicase goes through the DNA strand, single
stranded binding proteins cling to the sides of
the strand to keep them together.

4. 51
31
31
51
Helicase

5. Helicase

6. Helicase

7. Helicase

8. Helicase

9. Helicase

10. Helicase

11. Helicase

12. Helicase

13. Helicase

14. Helicase

15. Helicase

16. Helicase

17. Helicase

18. Helicase

19. Helicase

20. Helicase

21. Helicase

22. Step 2
Another enzyme, polymerase III, enters the
process. It reads from 31 to 51, but synthesizes
the corresponding bonds from 51 to 31.

23. Polymerase
III

24. Polymerase
III

25. Polymerase
III

26. Polymerase
III

27. Polymerase
III

28. Polymerase
III

29. Polymerase
III

30. Polymerase
III

31. Polymerase
III

32. Polymerase
III

33. Polymerase
III

34. Polymerase
III

35. Polymerase
III

37. Polymerase III then reads the parent strand and
synthesizes the other bases.

41. Step 3
DNA primase places an RNA primer from 51 to
31. The enzyme polymerase I changes that RNA
primer into DNA. DNA ligase forms
phosphodiester bonds. Adenine and thymine
form a double bond and cytosine and guanine
form a triple bond. When one of the purine
bases bonds with a pyrimidine base, they form a
quintuple (5) bond.

42. Results
After DNA replication takes place, you are left
with two identical DNA strands.

43. Parent Strand
Duplicate Strand

44. Purpose
Replication occurs so that the genetic material
can be passed from the original cell to the
daughter cell. This leads to the transfer of traits.

45. Meiosis
DNA Replication occurs in interphase.
Interphase is the period between the division of
two cells. During interphase, the cell increases in
size and makes a copy of the cells’ DNA to
prepare for the next division.

46. What are mutations?
A mutation is a permanent change in the DNA
sequence that makes up genes. They differ in
size from one DNA base to a large segment of
chromosomes.

47. How do we get them?
Mutations can be inherited from a parent. In
these cases, they are referred to as hereditary
mutations. Once acquired, they are permanent
throughout that person’s lifetime.

48. Mispairings
When a mispairing of bases occurs because of a
shifting in the position of the nucleotides, it is
called a wobble, one of a few different ways to
form a mutation.

49. Insertions or Deletions
When a nucleotide is inserted or deleted at the
wrong time or place, it creates another
mutation. This process is known as strand
slippage. A newly synthesized strand slightly
loops out, which causes an addition of an extra
nucleotide base. Sometimes, the template
strand becomes slightly misplaced. This results
in the deletion of nucleotide bases in the newly
synthesized strand.

50. Telomeres
• A compound structure at the end of an
eukaryotic chromosome
• Keep the ends of different chromosomes in
the cell from attaching to each other

51. Okazaki Fragments
Short, newly synthesized DNA fragments that
are formed on the lagging template strand
during DNA replication.

52. DNA Ligase
• A specific type of enzyme that facilitates the
joining of DNA strands together by catalyzing
the formation of a phosphodiester bond
• Seals breaks in the phosphate-sugar backbone
of DNA

53. Cancer
• Disease caused by an uncontrolled division of
abnormal cells in a part of the body
• Telomerase causes cancer cells to divide and
duplicate

54. Telomerase
• A ribonucleoprotein
• Adds telomere sequence to the 31 end of DNA
strands
• DNA polymerase then completes the synthesis
of the uncompleted ends of the other strand