Chapter 4, Lesson 3: DNA Replication and the Cell Cycle

Flashcards from Chapter 4, Lesson 3 of McGraw Hill Anatomy and Physiology, Ninth Edition, by Kenneth S. Saladin.

Law of Complementary Base Pairing

States that we can predict the base sequence of one DNA strand if we know the sequence of another

DNA replication steps

1. Unwinding

2. Unzipping

3. Building new strands

4. Repackaging

Replication fork

The point of DNA opening, this is made in step 1 after unwinding form histones

DNA helicase

The enzyme that unzips a segment of the DNA’s double helix structure in step 2

DNA polymerase

The enzyme that builds new DNA strands by matching free nucleotides to the unwinded DNA strand in step 3; the DNA is then repackaged and replicated for step 4

DNA Damage Response (DDR)

Mechanisms in place to correct replication errors by DNA polymerase; replaces unstable base pairs with correct pairs for a 1/1000000000 failure rate

Mutations

Changes in DNA structure due to replication errors or environmental factors; some may be harmless while others can cause defects or cancer later on

Cell cycle

The interphase and mitotic phases

Interphase

A part of the cell cycle that includes the first gap phase (G₁), synthesis phase (S), and second gap phase (G₂)

Mitotic phase

A part of the cell cycle that includes the prophase, metaphase, anaphase, telophase, and cytokinesis

First gap phase (G1)

Interval between cell birth and DNA replication; cell carries out normal tasks and accumulates materials for next phase

Synthesis phase (S)

Phase in interphase when the cell replicates all nuclear DNA and duplicates centrioles

Second gap phase (G2)

Interval between DNA replication and cell division; repairs errors and synthesizes enzymes

Mitotic phase

Phase where the cell replicates its nucleus

G zero phase (G0)

Cells that have left the cycle and ceased dividing for a long time

Mitosis

The cell division resulting in two genetically identical daughter cells; develops fertilized egg to 50 trillion cells and helps tissue growth

Phases of mitosis

1. Prophase

2. Metaphase

3. Anaphase

4. Telophase

Prophase

First phase in mitosis where genetic material condenses into compact chromosomes; nuclear envelope disintegrates and centrioles sprout spindle fibers

Metaphase

Second phase in mitosis where chromosomes align on the cell equator; microtubules extend from side to middle

Anaphase

Third phase in mitosis where the spindle fibers cleave chromatids apart to opposite poles of cell

Telophase

Fourth phase where chromosomes cluster on each side of the cell; the rough ER makes a new nuclear envelope and the mitotic spindles disintegrate

Cytokinesis

Divison of the cytoplasm into two cells where the cell pinches in two; comes after telophase

Cell division factors

Starts when:

• Adequate cytoplasm

• DNA replicated

• Nutrients supplied

• Cell stimulated

May stop when:

• Neighboring cells

• Nutrients or growth factors withdrawn