Cell Reproduction
Chromosomes: made of DNA
DNA: stores all genetic information
-genes: a hereditary unit of DNA
-4 bases:
-Adenine
-Thymine
-Guanine
-cytosine
Chromosome Anatomy
Chromosome Types
1. Sex Chromosomes:
determines the sex of
an organism
-XY: male
-XX: female
2. Autosomes: All other
chromosomes of an
organism
Chromosome Duplication
Homologous Chromosomes: two copies of each
autosome – same size, shape, and genes
Karyotype: photomicrograph of chromosomes
Humans have 22 pairs of autosomes and 1 pair of sex
chromosomes
Diploid Cells (2n): cells with both sets of
chromosomes (both homologous pairs)
46 chromosomes/23 pairs in humans
Haploid cells (1n): cells with one set of
chromosomes
“C” words of Cytology
1. Chromosome: condensed genetic material
2. Chromatid: one of two identical copies of
DNA
3. Centromere: region that joins the
chromatids
“C” words of Cytology
4. Centrioles: cylindrical
structures that assist
in cell division
5. Centrosome: dark
regions in the
cytoplasm that create
spindle fibers
Cell Division: all cells come from preexisting cells
2 Types of Division
1. Mitosis: cell division which
produces 2 diploid, identical cells
2. Meiosis: cell division which
produces 4 haploid cells
Cell Life Cycle
1. Interphase:
G1, S, and G2
G = growth
S = Synthesis
2. M phase:
mitosis –
nuclear
division
3. Cytokinesis:
cytoplasm
division
Interphase
1. Interphase: DNA not
visible
-nucleus still intact
Phases of Mitosis
2. Prophase:
chromosomes become
visible
-nucleus disintegrates
Phases of Mitosis
3. Metaphase:
chromosomes connect
at the centromere to
spindle fibers
-line up at the
equatorial plate
Phases of Mitosis
4. Anaphase: spindle
fibers recede
-pull chromosomes
apart
-chromosomes retreat
to opposite ends
Phases of Mitosis
5. Telophase: nucleus
reforms
Cytokinesis splitting
the cell
-2 daughter cells are
formed
21
22
23
24
Meiosis: cell division which produces
4 haploid cells
Haploid: a cell with half the number
of chromosomes (1n)
Fertilization: the fusion of two
gametes (sperm/eggs)
Review terms:
Homologous Chromosomes: same
chromosomes – one from each parent
Chromatid: one of two identical
copies of the same DNA
Meiosis
Meiosis
-produces four offspring
cells of 1n
-two cell division cycles
(meiosis I & 2)
-produces gametes
-chromosomes cross over
Mitosis Vs. Meiosis
8 Stages of Meiosis
Prophase I
Metaphase I
Anaphase I
Telophase I
Meiosis I
Prophase II
Metaphase II
Anaphase II
Telophase II
Meiosis II
Prophase I
-Tetrads form
Metaphase I
-Crossing over: exchange
of genetic info between
homologous
chromosomes
Anaphase I
-tetrads are pulled apart
Telophase I
-cytokinesis occurs
Prophase II
Metphase II
Anaphase II
Telophase II
Spermatogenesis: meiosis that
produces sperm
Produces 4 fertile cells; in humans @ 400
billion
Oogenesis: meiosis that produces egg
cells
Produces 1 fertile cell; about 400 in a lifetime
Types of Reproduction
1. Sexual reproduction: offspring are the result
of combination of parental genetics
2. Asexual reproduction: no exchange of
genetic information – genetically identical to
parent
Nature protects the female
Cellular Disorders
Cancer: a mitotic disorder
Characteristics:
1.
2.
3.
4.
Abnormal rates of cell division; uncontrolled
Produces malfunctioning cells
Kills the organism
Lack Density Dependent Inhibition (DDI)
Density Dependent Inhibition (DDI)
Ability of a cell to “sense” space – ability to stop
growth in a restricted space
Density Dependent Inhibition (DDI)
Lack of DDI – cells continue to divide –
causes tumors
Types of Tumors
1. Benign: cancer cells
remain at the original
site
2. Malignant: cancer
cells become
aggressive and spread
throughout the body
Teratoma
Metastasis: movement of cancer through the
blood/lymph to other organs
Causes: carcinogens and contributing
factors
-smoking
-radiation
-virus (HPV)
-genetic makeup
Treatments
-surgical removal
-radiation treatment
-chemotherapy: taxol, vincristine,
vinblastine
Cellular Differentiation
-begins following fertilization
-process by which generic cells gain specific
functions
-mitosis process
Stem Cells: undifferentiated cells that
can become any type of cell
Bone Cell
Neuron (nerves)
Muscle Cells
Skin Cells
Cardiac Muscle
Stem Cells