Cell Reproduction
Chromosomes: made of DNA
DNA: stores all genetic information
-genes: a hereditary unit of DNA-4 bases:
-Adenine-Thymine-Guanine-cytosine
DNA in the Cell
1. Chromosome2. Supercoil3. Subcoil4. One coil5. DNA with histine
protein6. DNA
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 material2. Chromatid: one of two identical copies of
DNA3. 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 pre-existing 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 Cycle1. Interphase:
G1, S, and G2G = 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 reformsCytokinesis splitting the cell-2 daughter cells are formed
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:
Karyotype
Homologous Chromosomes: identical chromosomes – one from each parent
Chromatid: one of two identical copies of the same DNA
Mitosis vs. Meiosis
Mitosis-Produces two offspring
cells of 2n-One cell division cycle-produces body cells-no chromosomes cross
over
Meiosis-produces four offspring
cells of 1n-two cell division cycles
(meiosis I & 2)-produces gametes-chromosomes cross over
8 Stages of Meiosis
Prophase IMetaphase IAnaphase ITelophase I
Prophase IIMetaphase IIAnaphase IITelophase II
Meiosis I
Meiosis II
Prophase I
-Chromatids form-Homologous chromatids
pair up to form tetrads
Metaphase I
-tetrads line up at equatorial plate
-Crossing over: breaking off of arms of chromatids and switching places on another homologous chromosome
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. Abnormal rates of cell division; uncontrolled2. Produces malfunctioning cells3. Kills the organism 4. 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
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
Stem Cells
Skin Cells
Neuron (nerves)
Bone Cell
Muscle Cells
Cardiac Muscle