Semiconservative — Science definition

Each copied duplex retains an original strand and gains a new complementary strand in the standard model.

Where it is taught

In use

Copying happens every time a cell prepares to divide, in a process called semiconservative replication.

DNA Structure & Replication

Questions using semiconservative

Problem 1

Explain why DNA replication is described as 'semiconservative.'
Answer and explanation

Each new DNA molecule is made of one original (conserved) strand and one newly built strand, so half of every copy is 'old.' That is what 'semiconservative' means.

Problem 2

Write the complementary strand opposite 5′-AACGTT-3′, then explain strand origin after one semiconservative round.
Answer and explanation

The directly paired complement is 3′-TTGCAA-5′. Each resulting duplex has one old template strand and one newly synthesized partner in the ideal model.

The directly paired complement is 3′-TTGCAA-5′. Each resulting duplex has one old template strand and one newly synthesized partner in the ideal model.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the biological mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Problem 3

Independent chapter check: Write the complementary strand opposite 5′-AACGTT-3′, then explain strand origin after one semiconservative round.
Answer and explanation

The directly paired complement is 3′-TTGCAA-5′. Each resulting duplex has one old template strand and one newly synthesized partner in the ideal model.

The directly paired complement is 3′-TTGCAA-5′. Each resulting duplex has one old template strand and one newly synthesized partner in the ideal model.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the biological mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Problem 4

Replication is described as semiconservative because each new double helix contains
  1. two new strands
  2. one original strand and one new strand
  3. only original strands
  4. a mixture of RNA and DNA
Answer and explanation

one original strand and one new strand

The two original strands separate and each serves as a template, so every product keeps one original strand.

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