DNA ReplicationBy John Matthews

P P

P P

P

PP

PP

P

PP

S S

S S

S S

S S

S S

A T

AT

A T

C

C

C SS

G

G

G

PPS SAT

S SCG

PP

PP

S SA T

This is a DNA molecule before it starts its journey in replication. The phosphates are above the sugars. The sugars have base pairs attached to them. Adenine with Thymine, and Guanine with Cytosine. Hydrogen bonds are in between the base pairs which hold them together.

A =Adenine

=Cytosine

=Thymine

=Guanine

=Sugar(Ribose)

=PhosphateP

G

S

C

T

DNA Replication

• Step 1. DNA Helicase is basically the starting point in DNA replication, it is an enzyme that splits apart. The DNA Replication takes place during the S Stage right after the G1 Stage and before the G2 Stage.

P P

P P

P

PP

PP

P

PP

S S

S S

S S

S S

S S

A T

AT

A T

C

C

C SS

G

G

GPP

S SAT

S SCGPP

PPS SA T

S S

SS

S S

P P

P

P

P

P

C

C G

G

H

H =DNA Helicase

DNA Helicase starts the process by splitting the bonds which create the Replication Fork

AT

DNA Replication

• Step 2. RNA Primase begins its binding. RNA Primase can attract nucleotides which bind to DNA nucleotides due to the hydrogen bonds between the bases

P P

P P

P

PP

PP

P

PP

S S

S S

S S

S S

S S

A T

AT

A T

C

C

C SS

G

G

GPP

S SAT

S SCGPP

PPS SA T

S S

SS

S S

P P

P

P

P

P

C

C G

G

AT

=RNA Primse

DNA Replication

• Step 3. The 5’3’ Leading strand begins its journey by reading the template and continuously adding nucleotides. The 3’5’ lagging strand adds more RNA primase creating gaps or fragments known as Okazaki fragments.

P P

P P

P

PP

PP

P

PP

S S

S S

S S

S S

S S

A T

AT

A T

C

C

C SS

G

G

GPP

S SAT

S SCGPP

PPS SA T

S S

SS

S S

P P

P

P

P

P

C

C G

G

AT

DNA Replication

• Step 4. In the Lagging strand the DNA Polymerase I removes the fragments. The gaps are closed with the action of DNA Polymerase, and DNA Ligase.-

3’ 5’

5’ 3’

5’ 3’

RNA PrimerRNA Primer

DNA Replication

• Step 5. The last step of DNA Replication is Termination. The DNA Polymerase reaches the ends of the strands. It is not possible for the DNA Polymerase to fill the gaps where the RNA Primers were. So the end of the parental strand where the last primer bind isn’t replicated. These ends consist of Telomeres. As a result a part of the Telomere is removed in every cycle of DNA Replication.

DNA Replication

• Step 6. DNA Replication is not complete until a mechanism of repairs fixes all possible errors caused during the replication. Enzymes like nucleases remove the wrong nucleotides and the DNA Polymerase fills the gaps.

3’ 5’

5’ 3’

5’ 3’

3’ 5’

Telomeres

• Telomeres are long stretches at the ends of the chromosome which are noncoding.

Okazaki Fragments

• Okazaki Fragments are when the replication fork opens sufficiently, DNA Polymerase can begin to synthesize a section of complementary strand.

DNA Ligase

• A DNA Ligase has the job of stitching the Okazaki Fragments together.

Telomerase

• Telomerase is an enzyme that adds telomere repeat sequences to the 3’ end of DNA strands. By lengthening this strand, DNA Polymerase is able to complete the synthesis of the “incomplete ends” of the opposite strand.

Cancer

• Cancer is different from the regular tissue due to its ability to grow indefinitely. Most 85-90% cancers express telomerase atleast in the population of cancer stem cells that divide uncontrollably causing the Tumor to grow.

Transplanted Cells

• Transplanted Cells are removing cells from the patient, and transforming them with the gene for the product that the patient has been unable to synthesize and return them to the patient.

Cloning

• Cloning is the replication of a single DNA molecule starting from a single living cell to generate a large population of cells containing identical DNA molecules.

Aging

• Aging is a syndrome of changes that are deleterious , progressive, universal and thus far irreversible. Aging damage occurs to molecules, cells, and organs.

The Purpose

• The purpose of DNA replication is to make an exact copy of DNA for other strands to be made. If DNA replication went wrong mutations could occur which could be fatal the that strand of DNA or to the human body all together.