By Pn. Aslizah Binti Mohd Aris 06-4832168
Jan 15, 2016
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
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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