DNA Replication

By: Alli Ishman

DNA Replication is the duplication of DNA during cell division. Replication takes place in the nucleus and starts at the origin of replication.

Adenine

Sugar (Deoxyribose)

Phosphate

Thymine

Guanine

Cytosine

3’

3’5’

5’

DNA Helicase unwinds double-stranded DNA at the origin of replication by breaking hydrogen bonds between complementary strands. In more simple terms, it is kind of like a zipper unzipping.

Adenine

Sugar (Deoxyribose)

Phosphate

Thymine

Guanine

Cytosine

DNA Helicase

Adenine

Sugar (Deoxyribose)

Phosphate

Thymine

Guanine

Cytosine

DNA Helicase

DNA Helicase unwinds double-stranded DNA at the origin of replication by breaking hydrogen bonds between complementary strands. In more simple terms, it is kind of like a zipper unzipping.

Adenine

Sugar (Deoxyribose)

Phosphate

Thymine

Guanine

Cytosine

DNA Helicase

DNA Helicase unwinds double-stranded DNA at the origin of replication by breaking hydrogen bonds between complementary strands. In more simple terms, it is kind of like a zipper unzipping.

Adenine

Sugar (Deoxyribose)

Phosphate

Thymine

Guanine

Cytosine

DNA Helicase

DNA Helicase unwinds double-stranded DNA at the origin of replication by breaking hydrogen bonds between complementary strands. In more simple terms, it is kind of like a zipper unzipping.

Adenine

Sugar (Deoxyribose)

Phosphate

Thymine

Guanine

Cytosine

DNA Helicase

DNA Helicase unwinds double-stranded DNA at the origin of replication by breaking hydrogen bonds between complementary strands. In more simple terms, it is kind of like a zipper unzipping.

Adenine

Sugar (Deoxyribose)

Phosphate

Thymine

Guanine

Cytosine

DNA Helicase

DNA Helicase unwinds double-stranded DNA at the origin of replication by breaking hydrogen bonds between complementary strands. In more simple terms, it is kind of like a zipper unzipping.

Adenine

Sugar (Deoxyribose)

Phosphate

Thymine

Guanine

Cytosine

DNA Helicase

DNA Helicase unwinds double-stranded DNA at the origin of replication by breaking hydrogen bonds between complementary strands. In more simple terms, it is kind of like a zipper unzipping.

Adenine

Sugar (Deoxyribose)

Phosphate

Thymine

Guanine

Cytosine

DNA Helicase

DNA Helicase unwinds double-stranded DNA at the origin of replication by breaking hydrogen bonds between complementary strands. In more simple terms, it is kind of like a zipper unzipping.

Adenine

Sugar (Deoxyribose)

Phosphate

Thymine

Guanine

Cytosine

DNA Helicase

DNA Helicase unwinds double-stranded DNA at the origin of replication by breaking hydrogen bonds between complementary strands. In more simple terms, it is kind of like a zipper unzipping.

Single-strand binding proteins react with the single-stranded regions of the DNA and stabilize it.

Single-strand binding protein

Adenine

Sugar (Deoxyribose)

Phosphate

Thymine

Guanine

Cytosine

5’

5’3’

3’

Adenine

Phosphate

Thymine

Guanine

Cytosine

Sugar (Deoxyribose)

RNA Primase

An RNA primase constructs an RNA primer to mark a starting point.

Adenine

Phosphate

Thymine

Guanine

Cytosine

RNA Primase

Sugar (Deoxyribose)

DNA Polymerase III

RNA Primer

DNA Polymerase III can then add deoxyribonucleotides to synthsize the new complementary strand of DNA. The leading strand adds nucleotides going down in the animation shown, and the lagging strand adds nucleotides going up in a discontinues fashion.

Adenine

Phosphate

Thymine

Guanine

RNA Primase

Sugar (Deoxyribose)

DNA Polymerase III

RNA Primer

Cytosine

DNA Polymerase III can then add deoxyribonucleotides to synthsize the new complementary strand of DNA. The leading strand adds nucleotides going down in the animation shown, and the lagging strand adds nucleotides going up in a discontinues fashion.

Adenine

Phosphate

Guanine

RNA Primase

Sugar (Deoxyribose)

DNA Polymerase III

RNA Primer

Cytosine

Thymine

DNA Polymerase III can then add deoxyribonucleotides to synthsize the new complementary strand of DNA. The leading strand adds nucleotides going down in the animation shown, and the lagging strand adds nucleotides going up in a discontinues fashion.

Adenine

Phosphate

Guanine

RNA Primase

Sugar (Deoxyribose)

DNA Polymerase III

RNA Primer

Cytosine

Thymine

DNA Polymerase III can then add deoxyribonucleotides to synthsize the new complementary strand of DNA. The leading strand adds nucleotides going down in the animation shown, and the lagging strand adds nucleotides going up in a discontinues fashion.

Adenine

Phosphate

Guanine

RNA Primase

Sugar (Deoxyribose)

DNA Polymerase III

RNA Primer

Cytosine

When the DNA polymerase III reaches the RNA primer on the lagging strand it is replaced by DNA polymerase I.

Thymine

Adenine

Phosphate

Guanine

Sugar (Deoxyribose)

DNA Polymerase III

RNA Primer

Cytosine

DNA Polymerase I

DNA polymerase I removes the RNA and replaces it with DNA.

Thymine

Adenine

Phosphate

Guanine

Sugar (Deoxyribose)

DNA Polymerase III

RNA Primer

Cytosine

DNA Polymerase I

DNA ligase

DNA ligase then attaches and forms phosphodiester bonds. This is just a bond between the phosphate of one nucleotide to the sugar of another nucleotide.

Thymine

Adenine

Phosphate

Guanine

Sugar (Deoxyribose)

DNA Polymerase III

RNA Primer

Cytosine

DNA Polymerase I

DNA ligase

Thymine

DNA ligase then attaches and forms phosphodiester bonds. This is just a bond between the phosphate of one nucleotide to the sugar of another nucleotide.

Adenine

Phosphate

Guanine

Sugar (Deoxyribose)

DNA Polymerase III

RNA Primer

Cytosine

DNA Polymerase I

DNA ligase

Thymine

Adenine

Phosphate

Guanine

Sugar (Deoxyribose)

DNA Polymerase III

RNA Primer

Cytosine

DNA Polymerase I

DNA ligase

Thymine

Adenine

Phosphate

Guanine

Sugar (Deoxyribose)

DNA Polymerase III

RNA Primer

Cytosine

Thymine

The DNA is further unwound, new primers are made, and DNA polymerase III begins synthesizing other okazaki fragments. Okazaki fragments are just short fragments of DNA made on the lagging strand during replication.

Adenine

Phosphate

Guanine

Sugar (Deoxyribose)

DNA Polymerase III

RNA Primer

Cytosine

Thymine

The DNA is further unwound, new primers are made, and DNA polymerase III begins synthesizing other okazaki fragments. Okazaki fragments are just short fragments of DNA made on the lagging strand during replication.

Adenine

Phosphate

Guanine

Sugar (Deoxyribose)

DNA Polymerase III

RNA Primer

Cytosine

Thymine

The DNA is further unwound, new primers are made, and DNA polymerase III begins synthesizing other okazaki fragments. Okazaki fragments are just short fragments of DNA made on the lagging strand during replication.

Adenine

Phosphate

Guanine

Sugar (Deoxyribose)

DNA Polymerase III

RNA Primer

Cytosine

Thymine

Again, once DNA polymerase III reaches the RNA primer it is replaced by DNA polymerase I.

Adenine

Phosphate

Guanine

Sugar (Deoxyribose)

DNA Polymerase III

RNA Primer

Cytosine

Thymine

DNA Polymerase I

DNA polymerase I removes the RNA primer.

Adenine

Phosphate

Guanine

Sugar (Deoxyribose)

DNA Polymerase III

RNA Primer

Cytosine

DNA Polymerase I

DNA ligase

DNA ligase then attaches and forms phosphodiester bonds. This is just a bond between the phosphate of one nucleotide to the sugar of another nucleotide.

Adenine

Phosphate

Guanine

Sugar (Deoxyribose)

DNA Polymerase III

RNA Primer

Cytosine

Thymine

DNA Polymerase I

DNA ligase

DNA ligase then attaches and forms phosphodiester bonds. This is just a bond between the phosphate of one nucleotide to the sugar of another nucleotide.

Adenine

Phosphate

Guanine

Sugar (Deoxyribose)

DNA Polymerase III

RNA Primer

Cytosine

Thymine

DNA Polymerase I

DNA ligase

DNA ligase then attaches and forms phosphodiester bonds. This is just a bond between the phosphate of one nucleotide to the sugar of another nucleotide.

Adenine

Phosphate

Guanine

Sugar (Deoxyribose)

DNA Polymerase III

RNA Primer

Cytosine

Thymine

DNA ligase

5’

5’3’

3’

What happens in DNA Replication?First DNA helicase unwinds the double helix shape of DNA. Then an RNA Primase constructs an RNA primer to mark a starting point. DNA polymerase III then adds nucleotides to make the new strand of DNA. When DNA polymerase III reaches the RNA primer, DNA polymerase I comes in and removes the primer and finally DNA ligase then attaches and forms phosphodiester bonds. DNA replication occurs during S phase in the nucleus.

In my own words• Telomeres- keep ends of various chromosomes in the cell

from accidentally becoming attached to each other• Okazaki Fragments- a section of the synthesized DNA on the

lagging strand• DNA Ligase- stick the okazaki fragments together like glue• Telomerase- an enzyme that adds telomere repeat sequence• Cancer- tissue that is able to grow in large amounts quickly• Transplanted Cells- cells that have been taken, added to and

then given back• Cloning- taking a piece of something and making another

copy• Aging- the steady shrinking of cells in the body

Why does DNA replicate?

If DNA did not replicate then there would be no DNA to pass on to the next generation, no way to provide the cell with the information necessary for processes, and no way to maintain the cell’s living.

Mistakes (Mutations)• DNA mutations happen when there are changes

in the nucleotide sequence that makes up the strand of DNA. This can be cause by random mistakes in DNA replication or even an environmental influence like UV rays or chemicals. Changing even just one nitrogen base in a sequence can change the amino acid that is expressed by the DNA codon which can lead to a completely different protein being expressed. These mutations range from being non-harmful all the way up to causing death.

Works Cited

• http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120076/micro04.swf::DNA Replication Fork

• http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120076/bio23.swf::How Nucleotides are Added in DNA Replication

• “DNA Helix.” Photograph. “Nucleobases and Their Production during the Photolysis of

Astrophysically-relevant Ices.” The Astrophysics & Astrochemistry Lab. NASA Ames Research Center, 2013. Web. 7 February 2014.