dna structure and replication

dna replication

DNA must replicate (copy) itself so that each resulting cell after mitosis and cell division has the same DNA as the parent cell. All these cells, the parent cell and the two new daughter cells, are genetically identical. DNA replication occurs during the S phase (the Synthesis phase) of the cell cycle, before mitosis and cell division. The base pairing rules are crucial for the process of replication. DNA replication occurs when DNA is copied to form an identical molecule of DNA. The general steps involved in DNA replication are as follows: 1. The DNA helix unwinds like a zipper as the bonds between the base pairs are broken. The enzyme DNA Helicase is involved in breaking these bonds. 2. The two single strands of DNA then each serve as a template for a new stand to be created. Using DNA as a template means that on the new strand, the bases are placed in the correct order because of the base pairing rules. Recall that A and T are complementary bases, as are G and C. As a template strand is read, the new strand is created. If ATGCCA is on the "template strand," then TACGGT will be on the new DNA strand. The enzyme DNA Polymerase reads the template and builds the new strand of DNA. 3. The new set of nucleotides then join together to form a new strand of DNA. The process results in two DNA molecules, each with one old strand and one new strand of DNA. This process is known as semiconservative replication because one strand is conserved (kept the same) in each new DNA molecule ( Figure 1.1). DNA replication occurs when the DNA strands unzip, and the original strands of DNA serve as a template for new nucleotides to join and form a new strand.

textbook_image

instructional diagrams

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questions

dna is replicated in a semiconservative manner.

-->  a. true

b. false

dna replication occurs prior to mitosis and cell division.

-->  a. true

b. false

what is the first step in dna replication?

a) a new strand of dna is created.

-->  b) the dna helix unwinds like a zipper.

c) the two strands of dna rewind into the double helix.

d) none of the above

what does semiconservative replication refer to?

a) both strands are new in each new dna molecule.

b) both strands are conserved in each new dna molecule.

-->  c) one strand is conserved and one strand is new in each new dna molecule.

d) none of the above

what is the template for a new dna strand during dna replication?

-->  a) both single strands of dna serve as a template during dna replication.

b) one single strand of dna serves as a template.

c) the opposite strand of dna serves as a template.

d) none of the above

if atcggatt is on the template strand, what dna sequence will be created?

a) atcggatt

b) atcccatt

-->  c) tagcctaa

d) taccctaa

when does dna replication occur?

a) the g1 phase of the cell cycle

-->  b) the s phase of the cell cycle

c) the m phase of the cell cycle

d) the r phase of the cell cycle

diagram questions

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