DNA replication

How does the polymerase aids in repairing DNA

(In addition to its ability to add nucleotides, it also performs repair function)-DNA polymerase proofread each nucleotide against its template as soon as it's added to the growing strand. When in finds an incorrectly paired nucleotide, it removes it & resumes synthesis

What is the main difference between DNA replication in Eukaryotes and Prokaryotes?

ENZYMES DNA polymerase in prokaryotes: Polymerase I, II, III Both initiation and elongation uses polymerase III. After elongation when the 2 daughter strands are made and the termination stage starts... the gap filling and DNA repair initiates, it is carried out by DNA polymerase I and II. The RNA primer is removed by the DNA polymerase I.

What is the second stage of DNA replication (explain)

Elongation Addition of new complementary strands. The choice of nucleotides to be added in the new strand is dictated by the sequence of bases on the template strand. New nucleotides are added one by one to the end of growing strand by an enzyme called DNA polymerase. The template strand specifies which of the four DNA nucleotides (A, T, C, or G) is added at each position along the new chain. Only the nucleotide complementary to the template nucleotide at that position is added to the new strand

DNA polymerase

Enzyme involved in DNA replication that joins individual nucleotides to produce a DNA molecule (In addition to its ability to add nucleotides, it also performs repair function)-DNA polymerase proofread each nucleotide against its template as soon as it's added to the growing strand. When in finds an incorrectly paired nucleotide, it removes it & resumes synthesis requires a primer to synthesis new strand on it DNA polymerase contains a groove that allows it to bind to a single-stranded template DNA and travel one nucleotide at time. For example, when DNA polymerase meets an adenosine nucleotide on the template strand, it adds a thymidine to the 3′ end of the newly synthesized strand, and then moves to the next nucleotide on the template strand. NB: Can only synthesize new strands in the 5' to 3' direction This process will continue until the DNA polymerase reaches the end of the template strand.

What is the first stage of DNA replication (explain)

INITIATION at the "origin of replication" which is where replication is initiated. An enzyme called "Helicase" unwind or unzips and separates the DNA helix into single stranded DNA by breaking the hydrogen bonds between the bases. As it opens, a Y shaped structure called "replication fork" is formed with 2 template forms. At the replication fork is where replication actually take place.

What do prokaryotic cell and eukaryotic cells use to remove RNA primers

Prokaryotic cell: DNA polymerase 1 (5' -> 3' exonuclease) Eukaryotic cells: RNase (5' -> 3' exonuclease)

what do the prokaryotic cells and eukaryotic cells use in the synthesis of DNA

Prokaryotic cell: DNA polymerase III Eukaryotic cells: DNA polymerase alpha and beta

How many origin of replications are there in prokaryotic cell and eukaryotic cells

Prokaryotic cell: one per chromosomes Eukaryotic cells: multiple per chromosome

Nuclease

DNA cutting enzyme that cut out the segment of DNA strand containing the damage. The resulting gap is then filled with nucleotides from DNA pol and glued by ligase.

DNA replication

The process by which DNA makes a copy of itself

What is the third stage of DNA replication (explain)

RNA primers need to be replaced with DNA, and nicks in the sugar-phosphate backbone need to be connected. this is done by the RNase. Once the primers are removed, a free-floating DNA polymerase lands at the 3′ end of the preceding DNA fragment and extends the DNA over the gap. "During termination, primers are removed and replaced with new DNA nucleotides and the backbone is sealed by DNA ligase" After ligase has connected all nicks, the new strand is one long continuous DNA strand, and the daughter DNA molecule is complete.

RNase

RNase H (DNA polymerase 1) removes RNA primers . RNA primers at the start of each leading strand and at the start of each Okazaki fragment, leaving gaps of unreplicated template DNA degrades RNA

What prevents the parents strands from binding back together after being separated

SSBPs (single stranded binding proteins) Bind to each template strand "exposed bases" and prevent them from binding together and "reforming" the double helix. Hence SSBPs prevents annealing of the template strands and stabilize the template strands

replication fork

a Y-shaped point that results when the two strands of a DNA double helix separate so that the DNA molecule can be replicated

How are the strands of DNA arranged and read

antiparallel and complementary The template strand is read in the 3′ → 5′ direction. A new strand of DNA is always synthesized in 5′ → 3′ direction.

What are the three stages of DNA replication

1. Initiation 2. Elongation 3. Termination

ligase

An enzyme that connects two fragments of DNA to make a single fragment. Joins the sugar phosphate backbone at the nick site

primase

An enzyme that joins RNA nucleotides to make the primer using the parental DNA strand as a template. builds RNA primers

In what stage in the DNA replication take place

Interphase

leading strand

Is synthesized continuously toward the replication fork as helicase unwinds the template double-stranded DNA. The new continuous complementary DNA strand synthesized along the template strand in the mandatory 5' to 3' direction. The leading strand can be copied continuosly because DNA polymerase is moving in the same direction as the unwinding enzyme helicase.

What is semi-discontinuous replication?

Leading strand is synthesized continuously but lagging strand is synthesized discontinuously.

What do prokaryotic cell and eukaryotic cells use to replace RNA with DNA

Prokaryotic cell: DNA polymerase 1 Eukaryotic cells: DNA polymerase alpha

Okazaki fragments

Small fragments of DNA produced on the lagging strand during DNA replication, joined later by DNA ligase to form a complete strand.

How much more DNA does eukaryotes have than prokaryotes

The amount of the eukaryotic DNA is around 50 times more than the prokaryotic DNA.

Movement of DNA polymerase

The leading strand can be copied continuosly because DNA polymerase is moving in the same direction as the unwinding enzyme helicase. For the other strand been synthesised, DNA polymerase is moving in the opposite direction from the helicase, which cause some bases to be exposed.

semi-conservative replication

in each new DNA double helix, one strand is from the original molecule, and one strand is new. The 2 new DNA molecules formed is made of 1 old (parent) strand and 1 new (daughter) strand.

Similarities between prokaryotes and eukaryotes DNA replication

1. They both use the helicase enzyme when unwinding the DNA double helix 2. they both use primase during the synthesis of RNA primers 3. They both use DNA ligase when joining Okazaki fragments 4. they both use single stranded DNA binding proteins in stabalizing of unwounded template strands 5. They both use DNA topoismerase II (DNA grase) to remove the positive supercouls ahead of advancing replication forks

primer

A short segment of DNA that acts as the starting point for a new strand A short segment (5-10 nucleotides) of RNA which is complementary to the template DNA strand. Needed to start the replication process. The RNA primer is synthesized by an enzyme, primase. DNA polymerase binds to the single stranded template DNA at the primer and move along the strand.

Helicase

An enzyme that untwists the double helix of DNA at the replication forks.

what is the difference between primase and polymerase

DNA primase forms an RNA primer, and DNA polymerase extends the DNA strand from the RNA primer.

True or False DNA replication is the same as Cell Division

FALSE DNA replication is not the same as cell division. Replication occurs before cell division, during the S phase of the cell cycle. Replication only concerns the production of new DNA strand not new cells.

Lagging strand

Is synthesized in the direction away from the replication fork and away from the DNA helicase unwinds. DNA is not synthesised continuously as some of the bases on the template strand are exposed as DNA polymerase is moving in opposite direction from helicase and this is called discontinuous replication. The strand that is synthesized in fragments using individual sections called Okazaki fragments

What is the process of DNA replication

The double-stranded structure of DNA suggested that the two strands might separate during replication with each strand serving as a template from which the new complementary strand for each is copied, generating two double-stranded molecules from one. The two strands of the DNA permanently separate from each other, new nucleotides line up along each original or parental strand of DNA. These new nucleotides join to form complementary strand along each half of the original or parental strand of DNA.

template DNA strand base paring

strand of DNA that is *copied* by RNA polymerase Each strand functions as a template for the new complementary daughter strand. In order to create a complementary strand (daughter strand) (A=T. C=G) If there is adenine in the parent or old strand, complementary thymine will be added to the new strand. Similarly, if there is cytosine in the parent strand, complementary guanine will be copied into the new daughter strand.