Download CHROMOSOMES, MITOSIS, MEIOSIS, AND MENDELIAN GENETICS

MODULE 8:
CHROMOSOMES, MITOSIS,
MEIOSIS, AND MENDELIAN
GENETICS
MODULE 8: PART I
Chromosomes and
Mitosis
Objectives

After completing this lab topic you should
be able to :


Describe the activities of chromosomes,
centrioles, and microtubules in the cell
cycle, including all phases of mitosis.
Describe differences in mitosis and
cytokinesis in plant and animal cells.
MITOSIS:
A process of cell (nuclear) division
characterized by a sequence of
distinctive stages that conserve
chromosome numbers by equally
allocating replicated chromosomes
to each of two daughter cells,
occurring in somatic cells.
 CHROMOSOMES:

Long, threadlike associations
of genes found in the nucleus
of all eukaryotic cells and
most visible during mitosis
and meiosis. Chromosomes
consist of DNA and protein.
Ploidy (N):
Term used to describe the number of
chromosomes of a certain type. Most
organisms are DIPLOID (2N), which means
their chromosomes occur in pairs; for
example a human has 46 chromosomes OR
23 pairs of chromosomes, (N=23; 2N=46).
Polyploidy:
A chromosomal alteration (e.g, mutation) in
which organism possesses more than two
complete chromosome pairs. (i.e.,
TRIPLOID (3N), TETRAPLOID (4N), etc.).
THE CELL CYCLE:
An ordered sequence
of events in the life
of a dividing cell,
composed of the G1,
S, G2, and M. G1. S,
and G2 are
collectively called as
Interphase (I).
The MITOTIC PHASE (M) consists of MITOSIS
(KARYOKINESIS = division of nucleus) and
CYTOKINESIS = division of cytoplasm.
1. PROPHASE:
•In nucleus
-nucleolus dissappear.
-each duplicated chromosome appear as two
identical sister chromatids joined at the
centromere.
• In cytoplasm
-the centrosome moves
away from each other.
-the spindle fibers
attach to the
chromosomes at
kinetochore site of
the centromeres.
2. METAPHASE:
-the centriole pairs are now at opposite
ends, or poles, of the cell.
-chromosomes are aligned with one another
at the equatorial (the metaphase plate) of
the cell.
.
ANAPHASE:
-each chromatid (now is
considered as a fullfledged chromosome)
move towards the
opposite poles.
-by the end of this
phase, the two poles
have equivalent and
complete collections
of chromosomes.
TELOPHASE followed by
CYTOKINESIS:
4.
- chromosomes gather at the two poles.
- nuclear envelopes are formed in this process
which is followed by cytokinesis or division of
cytoplasm which result in formation of two
daughter cells that have same number of
chromosomes.
CYTOKINESIS:
1). Animal type cytokinesis:
- occurs by process called cleavage.
- a contractile ring, pinch the parent cell to form
cleavage furrow that becomes deep and
pinch the two daughter cells away.
2). Plant type cytokinesis:
- no cleavage furrow.
- occurs by formation of cell plates across the
midline of the parent cell.
- the cell plates fuse together and separate the
two daughter cells.
Example of Mitosis in a plant cell:
Example of Mitosis in an animal cell:
Today’s lab will entail the
following:

Lab exercise to mimic mitosis using
pipe cleaners and beads (handout).