By Pn. Aslizah Binti Mohd Aris06-4832168

Chromosome morphology and function

The cell cycle and mitosis

Meiosis and gametogenesis

Here “chromosome” and “DNA” are not 100% synonymous

Chromosomes• Tightly packaged DNA• Found only during cell

division• DNA is not being used for

macromolecule synthesis

Chromatin• Unwound DNA• Found throughout

Interphase

• DNA is being used for macromolecule synthesis

Though chromosomes

are “all about”

DNA, in fact much this structure

consists of protein

Form via replication, not

by formed chromatids

coming together

1. A eukaryotic cell has multiple chromosome, one of which is represented here. Before duplication, each chromosome has a single DNA molecule.

2. Once replicated, a chromosome consists of two sister chromatids connected along their entire lengths by sister chromatidcohesion. Each chromatid contains a copy of the DNA molecule

3. Mechanical processes separate the sister chromatids into two chromosomes and distibute them to two daughter cells.Chromosomes DNA molecules

A chromatid is a chromatid as long as it is held in association with a sister chromatid at the centromere

Chromosome

Centromere Chromatid

Chromatid

When two sister chromatids separate (after metaphase) they go from being a single chromosome to being two different chromosomes

Genome =DNA

Chromosome =DNA + protein

(visible light microscope)

Chromatin =DNA + protein

(but less than for chromosome)DNA

Centromere

Centrosome

Centriole

Kinetochore

Kinetochore microtubules

Mitotic spindle

Nonkinetochore microtubles

Spindle apparatus

Spindle fibers

Centromere

Centrosome

Centriole

Kinetochore

Kinetochore microtubules

Mitotic spindle

Nonkinetochore microtubles

Spindle apparatus

Spindle fibers

Recall that the centrosome is the center of the microtubule array

of a cell

Centromere

Centrosome

Centriole

Kinetochore

Kinetochore microtubules

Mitotic spindle

Nonkinetochore microtubles

Spindle apparatus

Spindle fibers

Keep in mind that the term centriole is not an exact

synonym of centrosome and thatcentrosome is not a synonym of

the term centromere

Recall that these consist of microtubules and that a

pair makes up a centrosome

Centromere

Centrosome

Centriole

Kinetochore

Kinetochore microtubules

Mitotic spindle

Nonkinetochore microtubles

Spindle apparatus

Spindle fibers

Responsible for moving

chromosomes relative to mitotic

spindle

Centromere

Centrosome

Centriole

Kinetochore

Kinetochore microtubules

Mitotic spindle

Nonkinetochore microtubles

Spindle apparatus

Spindle fibers

These are the portion of the mitotic spindle that is

connected to chromosomes during

mitosis

Centromere

Centrosome

Centriole

Kinetochore

Kinetochore microtubules

Mitotic spindle

Nonkinetochore microtubles

Spindle apparatus

Spindle fibers

These are the microtubles that are responsible for separating

chromosomes as well as pushing the centrosomes toward

opposite ends of cells

Centromere

Centrosome

Centriole

Kinetochore

Kinetochore microtubules

Mitotic spindle

Nonkinetochore microtubles

Spindle apparatus

Spindle fibers

Microtubules of mitotic spindle that are not

connected to the chromosomes but

instead responsible for pushing centrosome

apart

Centromere

Centrosome

Centriole

Kinetochore

Kinetochore microtubules

Mitotic spindle

Nonkinetochore microtubles

Spindle apparatus

Spindle fibers

The mitotic spindle as visible through a light

microscope

Centromere

Centrosome

Centriole

Kinetochore

Kinetochore microtubules

Mitotic spindle

Nonkinetochore microtubles

Spindle apparatus

Spindle fibers

Bundles of microtubles making up the spindle

apparatus; it is the bundling that makes

them visible through a light microscope

“G” stands for “Gap”

Mitosis is conventionally divided into five phases: Prophase Prometaphase Metaphase Anaphase Telophase

Cytokinesis is well underway by late telophase

BioFlix: MitosisBioFlix: Mitosis

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MITOSIS

Cytokinesis can occur simultaneous

to telophase

Nucleus defined

Nucleoli present

Replicated Centrosomes

Asters present

DNA duplicated

DNA still chromatin

Chromatic condensation

Nucleoli disappear

Mitotic spindle forms

Centrosome separation

Nuclear envelope fragments

Microtubules invade nucleus

Microtubles interact chromosomes

Kinetochores at centromeres

Chromosomes jerky movements

Nonkinet. microtubule interaction

Centrosomes opposite poles

Metaphase plate

Chromosomes straddle MP

Kinetochores attached KMT

Spindle apparatus

Brief, static phase

Begins with “sister” separation

Chromatids now chromosomes

“Sisters” to opposite poles

Movement centromere first

Non-kinet. microtu. lengthening

Further separation of poles

Non-kinet. microtu. lengthening

“Sisters” at opposite poles

Nuclear env. reformation

Reforms from endomembrane

Chromosome decondensation

Cytokinesis already under way

In animal cells, cytokinesis occurs by a process known as cleavage, forming a cleavage furrow

In plant cells, a cell plate forms during cytokinesis

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cleavage Furrow