Question

dna replication
before a cell divides, its dna is replicated (duplicated.) after division, it is essential both cells end up with complete instructions as the cell will eventually divide again. because the two strands of a dna have complementary base pairs, the nucleotide sequence of each strand automatically supplies the information needed to produce its partner. if the two strands of a dna molecule are separated, each can be used as a pattern or template to produce a complementary strand. each template and its new complement together then form a new dna double helix, identical to the original. since each produced strand contains one parent strand, dna replication is said to be semi - conservative.

before replication can occur, the length of the dna double helix about to be copied must be unwound. in addition, the two strands must be separated, much like the two sides of a zipper, by breaking the weak hydrogen bonds that link the paired bases. once the dna strands have been unwound, they must be held apart to expose the
bases so that new nucleotide partners can
hydrogen - bond to them.

the enzyme dna polymerase then moves along
the exposed dna strand, joining newly arrived
nucleotides into a new dna strand that
is complementary to the template. at the end, two
strands identical to each other are produced.

1. why do cells need to replicate their dna

before dividing?

1. each strand acts as a ____________ for a

new strand to be created from.

1. before a strand can start to be replicated,

what needs to happen?

1. what enzyme builds the new dna strand?
2. once dna replication is over, are the two strands alike in any way?
3. fill in the matching base pairs using the model below.

base pairing boxes: agactcagg, tctgagtcc, etc.

Explanation:

Question 1

Cells divide to produce new cells. For the new cells to function properly, they need the same complete set of genetic instructions (DNA) as the original cell. So DNA replication before division ensures each new cell gets a full copy of DNA.

From the text: "If the two strands of a DNA molecule are separated, each can be used as a pattern or template to produce a complementary strand." So each strand acts as a template.

The text says: "Before replication can occur, the length of the DNA double helix about to be copied must be unwound. In addition, the two strands must be separated... by breaking the weak hydrogen bonds... Once the DNA strands have been unwound, they must be held apart to expose the bases..." So the DNA double helix must be unwound, the two strands separated (by breaking H - bonds), and held apart to expose bases.

Answer:

To ensure that after cell division, each new cell ends up with a complete set of DNA (genetic instructions) so the cell can function properly and divide again in the future.

Question 2