A&P: Cellular Biology II

anatomy and physiology walked so anthony could run

Nucleus

Nucleus

Contains genetic material (DNA) and directs cell activity; located near the center of the cell.

Nuclear Envelope

Composed of two membranes with nuclear pores that allow molecule movement between the nucleus and cytoplasm.

Nucleolus

Dense region within the nucleus where ribosome subunits are made.

Chromatin

Composed of DNA and histones, organized into chromosomes.

Nucleosomes

Structural units of chromosomes consisting of DNA wrapped around histones.

Cell Cycle

The series of changes a cell undergoes from formation until division, including interphase and cell division (mitosis).

Interphase

The phase where the cell carries out metabolic activities and prepares for division; consists of G1, S, and G2 subphases.

G1 Phase

Cell carries out regular metabolic activities.

S Phase

Synthetic phase, DNA replication (duplication of chromosomes) occurs.

G2 Phase

Brief growth period for synthesizing proteins necessary for division. Cell prepares for cell division.

G1 Checkpoint

Also known as the restriction checkpoint, as it causes cells to stay in G0.

This checkpoint ensures that the cell has adequate resources to go through the cell cycle.

G0 Phase

Stops cell division or causes apoptosis.

G2 Checkpoint

Checks for DNA damage and ensures that DNA replication is fully complete.

Spindle Checkpoint

Ensures all chromosomes are correctly attached to spindle fibers before anaphase.

Two major parts of cell division

Mitosis and Cytokinesis

Mitosis

The process of dividing chromosomes into new nuclei, resulting in two genetically identical diploid daughter cells. Used for somatic cells.

Cytokinesis

The division of the cytoplasm into two new cells, beginning at telophase.

Phases of Cytokinesis

Formation of a cleavage furrow

Contractile ring pulls membrane inward and splits the cell in half

Contractile ring is made up of actin filaments

Phases of Mitosis

Prophase, metaphase, anaphase, and telophase.

Prophase

1. Centrioles move to other ends of the cell

2. Chromatin becomes dense to make mitotic chromosomes 

   1. Each copy is a chromatid, attached to the centromere (center)

   2. A protein called the kinetochore binds the centromere, providing a point of attachment for the microtubules to come and separate during mitosis

3. Sister chromatids are connected by the centromere

4. Nucleoli disappear

5. Spindle fibers form and attach to kinetochore on chromosome.

Metaphase

Chromosomes align to the center (metaphase plate) of the cell.

Anaphase

1. Centromeres split, chromatids separate

2. Sister chromatids are pulled to opposite ends of the cell by the kinetochore fibers contracting

   1. Resulting in a V-shape

   2. Shortest stage of mitosis

Telophase

1. Chromosome movement halts

2. Nuclear envelope forms around the chromosomes

3. Chromosomes uncoil back to chromatin

4. Mitotic phase is completed

Meiosis

A specialized type of cell division for gametes, resulting in four daughter haploid cells with half the number of chromosomes. Used for gametes.

Goes through the cell division phase twice.

Crossing Over

Part of the chromatid breaks down and is exchanged with another chromatid. Results in a new genetic combination- occurs in meiosis prophase I.

Chiasmata

Points where the chromatids cross over.

Synapsis

Homologous chromosomes come together to form tetrads.

Prophase I

1. 46 duplicate chromosomes (2 sister chromatids) connected by the centromere.

2. Chromosomes become visible

3. Nuclear membrane disappears

4. Homologous pairs come together in a process called synapsis— the homologous chromosomes form tetrads. 

   1. Part of the chromatid of one homologous chromosome breaks off and is exchanged with another chromatid. This is called crossing over, and results in a new genetic combination. Crossover points are called chiasmata.

Metaphase I

1. Homologous pairs line up in the middle of the cell

However, alignment is random. Combined with crossing over, the genetic recombination is the cause of diversity of genetic composition in sperm cells and oocytes.

Anaphase I

1. Chromosomes of homologous pairs separate to opposite ends of the cell

2. Centromeres do not break, sister chromatids remain attached

Telophase I

1. Chromatids decondense into less visible chromatin.

2. New nuclei form

3. Meiosis I is completed

Meiosis II

The same as mitosis, but without interphase S.

Cancer

Unchecked growth of genetically abnormal cell.

Carcinoma

• Originates from epithelial tissue

  • Glandular

  • Squamous

  • Melanocyte

Sarcoma

• Originates from connective tissue

  • Cartilage

  • Bone

  • Fibrous connective

  • Meninges

  • Think: co- in connective with co- in sarcoma

Cancer will not occur in cells that do not ___

Replicate

Neoplasia

The increase of new cells, which can lead to tumor formation.

Benign Tumors

Tumors that resemble normal tissue, grow slowly, and do not invade other tissues.

Malignant Tumors

Poorly differentiated tissues that grow rapidly, destroy nearby tissue, and can metastasize.

Dystrophy

A disorder that arises from abnormal cell size.

Hypertrophy

Increase of cell size.

Atrophy

Decrease in cell size.

Dysplasia

A disorder that arises from abnormal cell growth.

Hyperplasia

Increase in cell growth.

Aplasia

Too little growth (loss of function).

Epidemiology

The study of disease and factors that lead to cancer, focusing on risk factors.

Cancer Host Factors

• Age

• Sex

• Psychological Factors

• Genetic Factors

Cancer Environmental/Lifestyle Factors

• Geographical location

• Nutrition

• Occupation (exposure to certain chemicals/pollutants)

  • Asbestos

  • Pesticides

  • Radiation

• Cigarette smoking

Etiology

The complex causes of diseases, often involving DNA damage and inadequate physiological defense.

Neoplastic Transformation

The initiation of cancer cells arising from a single cell that suffers multiple genetic mutations.

Inherited, acquired

Mutations are [ ] and [ ].

Proto-oncogenes

Plays a role in regulating normal cell division. Helps cells grow and divide to make new cells or helps keeps cells alive. When infected with cancer, becomes genes (oncogenes) that induce cell proliferation or growth.

Tumor Suppressor Genes

Regulates cell division. Inhibit growth of damaged cells. If DNA replicates errors, these genes edit out most of them. Opposite of oncogenes.

Cancer Treatment

Various methods including surgery, radiation therapy, chemotherapy, bone marrow transplantation, biological response modifiers, and gene therapy.