Can someone please describe DNA replication and all of the steps?

Question

When you are describing it, remember this, make it understandable to a ninth grader. Please be very descriptive and define things and words I might not know and that you think I might not know.

Now when the enzyme breaks the DNA strand into two, what are those two pieces called? RNA, DNA, strands, or what?

Answer 1

Consider that the DNA molecule is composed of two strands which are antiparalell to each other (meaning that they are held together in opposite directions) Also that DNA replicates in a semiconservative way, meaning that there will be a parental strand and a new strand of DNA in each doughter DNA molecule.

First, the double helix becomes separated in a specific sequence of nucleotides (recognized by proteins) forming a "bubble" known as an origin of replication.

From this origin of replication, an enzime calle helicase unwinds the molecule until the next origin of replication.

Already unwind, another enzime, primase, will add a primer (a short nucleotide chain of either DNA or RNA) to both strands. It is important to notice that one strand will be a "leading strand" and the other a "lagging strand". This happens because the enzimes only work from the 5' (5 prime) end to the 3'. Since the strands are antiparalell, your strand will look like this:

3'-ACGTACGT-5' *my replication will be in --> direction
5'-TGCATGCA-3'

So, primase will place a primer in the 5' (since it has a 3' to pair it with). Now, using my DNA strands above, the strand containing the 5' first (the one on the bottom in this case) will continue a constant replication when another enzime, DNA polimerase III, adds nucleotides that pair with the template strand. This will be the leading strand.

Then the other strand, the one strarting with the 3', will add many primers in order to have the necessary 5' end available for the addition of nucleotides. It will use again the enzime DNA polimerase III. Notice that the strand will be replicated in sections separated by the primers. These fragments are called "Okazaki fragments". The primer will be substituded by DNA by the enzime DNA polimarase I and will be glued together by yet another enzime called DNA ligase.

By the end ot this you will have two identycall DNA molecules!

I hope this is not too complicated.... BEST OF LUCKS!!!!

Answer 2

DNA in a living cell is a coil of two long molecules, linked together. Each of these strands is like beads on a string; each bead is a submolecule called a base, and there are four different kinds. A base on one strand has a corresponding complementary base on the other. The replication process begins by unwinding the coil and separating the strands, then adding new bases which are complementary to those in the strand. By the time this is done, the separated strand has been re-created. Now the cell can fission, and give to each daughter cell a full complement of DNA.

Answer 3

DNA starts with one molecule of DNA and ends with two identical molecules of DNA.

1. An enzyme "unzips" the DNA down the middle by separating the base pairs. If you picture DNA being a ladder, it separates in the middle of the steps.
2. Other enzymes match new nucleotides with the unzipped bases. (A nucleotide is a building block of DNA. A nucleotide has a sugar, a phosphate, and a nitrogen base.) These new nucleotides are like spare parts that are waiting to be used. Adenine matches with thymine, and guanine matches with cytosine. I teach my classes that you put the letters with straight lines together - A-T and the letters with round parts together - C-G.
3. When all the new parts are fastened in, the new molecules twist up and you have two new DNA molecules. Each new DNA has one side that is from the original DNA and one side that is made from new nucleotides matching in.

http://www.pbs.org/media/evolution/library/06/3/l_063_02_ref.mov