Page 108 - Genetics_From_Genes_to_Genomes_6th_FULL_Part1

100 Chapter 4 The Chromosome Theory of Inheritance

Figure 4.10 Mitosis maintains the chromosome number of the parent cell in the two daughter nuclei. In the
photomicrographs of newt lung cells at the left, chromosomes are stained blue and microtubules appear either green or yellow. Note that the
drawings are of Ascaris cells (2n = 4).
a–f: © Photomicrographs by Dr. Conly L. Rieder, Wadsworth Center, Albany, New York 12201-0509
In animal cells
Centriole

Microtubules
Centrosome (a) Prophase: (1) Chromosomes condense and
become visible; (2) centrosomes move apart
Centromere
toward opposite poles and generate new
Chromosome microtubules; (3) nucleoli begin to disappear.
Sister chromatids
Nuclear envelope

Astral microtubules
Kinetochore (b) Prometaphase: (1) Nuclear envelope breaks
down; (2) microtubules from the centrosomes
Kinetochore invade the nucleus; (3) sister chromatids attach
microtubules to microtubules from opposite centrosomes.
Polar
microtubules

Metaphase
plate

(c) Metaphase: Chromosomes align on the
metaphase plate with sister chromatids facing
opposite poles.

Separating sister
chromatids

(d) Anaphase: (1) The connection between the
centromeres of the sister chromatids is severed;
(2) the now separated sister chromatids move to
opposite poles.

Re-forming
nuclear envelope
(e) Telophase: (1) Nuclear membranes and
nucleoli re-form; (2) spindle fibers disappear;
(3) chromosomes uncoil and become a tangle
of chromatin.
Nucleoli reappear
Chromatin

(f) Cytokinesis: The cytoplasm divides, splitting
the elongated parent cell into two daughter
cells with identical nuclei.