The Cellular Basis of Reproduction & Inheritance

Nucleus: Membrane-bound organelle that contains genetic material.
Chromatin: The less condensed form of DNA, where the DNA is loosely packed with proteins.
Nucleolus: A dense region within the nucleus responsible for ribosome synthesis.
Microtubules: Structural components of the cytoskeleton involved in cell division.
Centrosome: An organelle that serves as the main microtubule organizing center and plays a key role in cell division.

Chromosome: A structure that carries genetic information.
Duplicated Chromosome: A chromosome that has undergone DNA replication, consisting of two identical sister chromatids joined at the centromere.

Mitosis: A process of cell division resulting in two genetically identical daughter cells, primarily involved in producing somatic cells.
Daughter cells are diploid, having the same chromosome number as the parent cell.

Interphase: The stage of the cell cycle where the cell prepares for division. It includes three phases:
- G1 Stage: Cell growth and organelle synthesis.
- S Phase: DNA replication, during which the centrosome and chromosomes duplicate.
- G2 Stage: Additional growth and organelle synthesis to prepare for mitosis.
Mitosis: Includes the following stages:
- Prophase: The nuclear envelope begins to fade, and centrosomes move to opposite poles of the cell.
- Metaphase: The nuclear membrane is dissolved, and sister chromatids line up in the center of the cell, with microtubules emerging from centrosomes to attach to sister chromatids.
- Anaphase: Microtubules pull sister chromatids apart.
- Telophase: A new nuclear envelope begins to form around the separated chromatids.
Cytokinesis: The final stage where the cytoplasm divides:
- Animal Cells: Form a cleavage furrow, indenting the membrane.
- Plant Cells: Form a cell plate that develops into a new cell wall.

G1 Checkpoint: Checks for DNA damage. If damage is found:
- The cell is sent to G0 (non-dividing state).
- p53 protein attempts repair; if unsuccessful, apoptosis occurs.
G2 Checkpoint: Ensures that DNA has been replicated correctly. Similar action occurs if problems are detected.
M checkpoint: Verifies that chromosomes are accurately distributed to daughter cells.

Out of Control Cell Cycle: In cancerous cells, cell cycle checkpoints fail to function leading to uncontrolled division.
Mutations: Permanent changes in the DNA can lead to cancer development (carcinogenesis).
Tumor Formation: Tumors can be benign (remain in the original site) or malignant (invade other body parts).
Mechanisms of Cancer Growth: Includes processes such as:
- Angiogenesis: Growth of new blood vessels to supply nutrients to tumors.
- Metastasis: Spread of cancer cells to new locations in the body.

Cancer cells typically exhibit:
- Abnormal nuclei (larger, irregularly shaped).
- An increased number of dividing cells with disorganized arrangements.
- Variability in size and shape of cells compared to normal cells.

Possible genetic links:
- BRCA1 Mutation: Associated with a 55-65% risk of breast cancer.
- BRCA2 Mutation: Associated with a 45% risk.
Normal BRCA: Associated with a 12% risk of developing breast cancer.

Henrietta Lacks (1920-1951): Cells taken without consent, leading to the first immortalized human cell line (HeLa cells).
- Cells did not die and contributed to substantial medical advancements.
- Ethical concerns regarding consent highlighted in the publication "The Immortal Life of Henrietta Lacks".

Exploration of various cancer types including:
- Lung cancer
- Skin cancer
- Breast cancer
- Gastrointestinal cancer
- Prostate cancer
- Oral cancer
- Colon cancer
- Uterine cancer
- Cervical cancer
Key points for study:
- Identify typical symptoms.
- Discuss genetic links.
- Evaluate treatment options.
- Discuss prevention strategies for each type.

Gametogenesis: The creation of gametes (sperm and eggs) that are genetically different from each parent cell, inherent in sexual reproduction.
Human chromosomes: 23 pairs (46 total), categorized as:
- Homologous Pairs: 22 pairs of autosomes and 1 pair of sex chromosomes (XY males, XX females).

Meiosis: Involves two divisions resulting in four haploid daughter cells (gametes) which are genetically diverse. These then unite during fertilization to form a diploid zygote.

Prophase I: The nuclear envelope begins to fade. Crossing-over occurs, enhancing genetic variation through random exchange of genetic material.
Metaphase I: Homologous chromosomes align randomly on the spindle.
Anaphase I: Homologues separate (moving to opposite poles).
Telophase I: Nuclear envelope reforms around each new nucleus, reducing chromosome number to haploid.
Cytokinesis I: Divides the cytoplasm into two daughter cells.

Followed after a brief resting phase, Interkinesis.
Prophase II: Nuclear envelope fades again.
Metaphase II: Sister chromatids align in the center of each cell.
Anaphase II: Sister chromatids are separated.
Telophase II: Nuclear envelope reappears.
Cytokinesis II: Four haploid daughter cells result from two cells, each still haploid.

Nondisjunction: A failure of homologous chromosomes or sister chromatids to separate during meiosis, leading to gametes with an abnormal number of chromosomes.
Aneuploidy: Result from nondisjunction. It includes:
- Trisomy: Presence of an extra chromosome (e.g., Trisomy 21 results in Down Syndrome).
- Monosomy: Absence of a chromosome.

Turner Syndrome: A form of monosomy where females possess only one X chromosome, leading to developmental issues including not undergoing puberty.
Klinefelter Syndrome: A condition leading to males having two or more extra X chromosomes, resulting in various physical and cognitive effects.