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