Cellular Reproduction Lecture Review

Cellular Reproduction Key Terms

• Somatic Cells: Typical body cells containing 46 chromosomes, arranged in 23 pairs. These cells make up tissues, organs, and systems of the body.

• Chromosome: A long DNA molecule associated with proteins called histones that compact DNA into a manageable structure. Each chromosome carries many genes, the units of heredity.

• Chromatin: The complex of DNA and proteins that forms chromosomes within the nucleus of eukaryotic cells. Chromatin undergoes condensation to form visible chromosomes during cell division.

• Centromere: The region of a condensed chromosome where sister chromatids are joined. It plays a crucial role in the separation of chromosomes during cell division.

• Gamete: A haploid reproductive cell (sperm in males, egg in females) that fuses during fertilization to form a zygote.

• Haploid: Cells that have only one complete set of chromosomes, resulting in 23 chromosomes in human gametes.

• Zygote: A fertilized egg formed by the union of a sperm and an egg, which is diploid and contains 46 chromosomes. It represents the earliest stage of development in a new organism.

• Diploid: Cells that contain two sets of homologous chromosomes (2n). In humans, this means 46 chromosomes total, with half from each parent.

Chromosome Types

• Autosome: The first 22 pairs of chromosomes in humans that are not involved in determining sex.

• Karyotype: An orderly display of an individual's chromosomes, typically arranged in pairs according to size and shape. It can be used to diagnose genetic disorders.

• Clone: A group of genetically identical offspring derived from a single parent. This can occur naturally, through asexual reproduction, or artificially in laboratory settings.

DNA Structure

• Nucleotide Components: Each nucleotide, the building block of DNA, consists of three parts: a phosphate group, a five-carbon sugar (deoxyribose), and a nitrogen base (adenine, thymine, cytosine, or guanine).

• Single Strand of DNA: The strand of DNA made up of a sequence of nucleotides connected by covalent bonds. The sequence of bases encodes genetic information.

• Double Helix Formation: The structure formed by two strands of DNA winding around each other, stabilized by hydrogen bonds between complementary base pairs (A with T, and C with G). This design is critical for replication and function.

Karyotype

• Definition: A photographic inventory of chromosomes in an individual, used in genetics and medical diagnostics to identify chromosomal abnormalities.

• Example: A human karyotype can show 46 chromosomes with a notation of 46 XY for males (indicating one X and one Y chromosome) or 46 XX for females (indicating two X chromosomes).

Types of Cell Division

• Cell Division Necessity: Essential for both unicellular and multicellular organisms for purposes of growth, repair, and reproduction.

• Binary Fission Process in Bacteria: A straightforward method of asexual reproduction wherein prokaryotic cells split into two identical daughter cells.

  • Stages:

    1. Cell elongation: The bacterial cell grows and elongates.

    2. DNA Replication: The circular DNA is duplicated, resulting in two identical sets of DNA.

    3. Cell Division: The cell membrane pinches inward, dividing the cytoplasm and resulting in two daughter cells.

Mitosis Overview

Will be on the test:

• Definition: The process of cell division in eukaryotic cells that results in two genetically identical daughter cells for purposes of growth and repair.

  • Stages in Mitosis:

    • Interphase: The preparation phase where the cell spends 90% of its cycle, undergoing normal functions and preparing for division.

    • Prophase: Chromatin condenses into visible chromosomes, and the nuclear envelope breaks down. Spindle fibers form from the centrosomes.

    • Metaphase: Chromosomes align at the cell's equator, ensuring proper distribution to daughter cells. This lines up in the center of the cell.

    • Anaphase: Sister chromatids separate and move to opposite poles of the cell.

    • Telophase: Chromatids reach the opposite poles, decondense back to chromatin, and nuclear envelopes reform around each set of chromosomes.

Cytokinesis

• Definition: The process where the cytoplasm of a parental cell divides into two daughter cells, completing the cell division cycle. Each daughter cell receives an identical set of organelles and genetic material.

The Mitotic Cell Cycle

• Phases:

  • M Phase: This phase includes both mitosis and cytokinesis, where actual cell division occurs.

  • Interphase: 90% of the cell cycle, consisting of three sub-phases:

    • G1 Phase: The cell grows, carries out normal functions, and prepares for DNA replication.

    • S Phase: Replication of DNA occurs, resulting in doubled chromosomes (thus each chromosome consists of two sister chromatids).

    • G2 Phase: Further growth and preparation for cell division, including the synthesis of proteins required for mitosis.

Meiosis Overview

• Definition: A specialized form of cell division that occurs in sexually reproducing organisms, where a diploid parent cell divides twice to create four haploid daughter cells, contributing to genetic diversity.

• Purpose: The shuffling of genes through processes like independent assortment and crossing over promotes genetic variation.

Stages of Meiosis I

• Prophase I: Homologous chromosomes pair and undergo crossing over, exchanging genetic material to enhance diversity.

• Metaphase I: Paired homologous chromosomes align at the cell's equator, preparing to separate.

• Anaphase I: Homologues separate and move to opposite poles while sister chromatids remain attached.

• Telophase I: Two nuclei form around the separated chromosomes, resulting in two haploid daughter cells.

Meiosis II

• Process: Similar to mitosis, however, it occurs in two haploid cells.

  • Prophase II: Spindle apparatus forms anew in each haploid cell.

  • Metaphase II: Chromosomes line up at the equatorial plane of the cells.

  • Anaphase II: The sister chromatids separate and move toward opposite poles.

  • Telophase II: Results in four haploid daughter cells, each genetically distinct due to prior crossing over and independent assortment.

Comparison: Mitosis vs. Meiosis

• Mitosis: Produces 2 identical daughter cells for growth and repair.

• Meiosis: Produces 4 genetically diverse haploid cells for sexual reproduction.

• Crossover: A critical event unique to meiosis during prophase I that enhances genetic variation between gametes.

Cancer Overview

• Statistics: Approximately 500,000 Americans die from cancer each year; statistics suggest 1 in 3 individuals will be diagnosed with cancer during their lifetime.

• Common Types: Includes lung cancer, colorectal cancer, breast cancer, and prostate cancer, each with distinctive risk factors and treatment strategies.

Terminology

• Tumor: An abnormal mass of tissue that results from unregulated cell growth. Tumors can be benign (non-cancerous) or malignant (cancerous).

• Neoplasm: A new and abnormal growth of tissue, which can be benign or malignant.

• Benign vs. Malignant: Benign tumors do not generally invade surrounding tissues or spread, while malignant tumors have the potential to metastasize, spreading cancer cells to other parts of the body.

Cancer Characteristics

• Causes: Carcinogenesis is often linked to uncontrolled cell growth due to DNA mutations resulting from environmental factors or inherited genetic predispositions.

• Risk Factors: Include but are not limited to exposure to radiation, harmful chemicals, viral infections, and genetic vulnerability.

Cancer Types

• Carcinoma: A type of cancer originating from epithelial cells that line internal organs and structures.

• Sarcoma: Cancer that arises from connective tissues, such as bone, cartilage, fat, and blood vessels.

• Leukemia: A cancer of the blood-forming tissues, usually resulting in the overproduction of abnormal white blood cells.

How Cancer Spreads

• Through lymphatic and circulatory systems: Cancer cells can travel through these systems to invade other tissues and organs, forming secondary tumors.

• Metastasis: The process whereby cancer cells spread from the primary site to other areas in the body, presenting a significant challenge in treatment.

Ovarian Cancer Challenges

• Symptoms: Often subtle or absent in the early stages; common symptoms may include abdominal swelling or discomfort, difficulty eating, or urinary urgency.

• Survival Rates: Highly variable based on the stage at diagnosis, with early detection improving outcomes significantly.

Signs of Cancer

• Common indicators include changes in bowel habits, non-healing sores, unusual bleeding, new lumps, unexplained weight loss, and fatigue.

Detection Methods

• Blood Tests: Used to check for specific tumor markers or abnormalities indicative of cancer.

• Biopsy: A procedure in which tissue samples are taken from suspected tumors for microscopic analysis, crucial for differentiating between benign and malignant growths.

Treatment Options

• Surgery: Involves the removal of tumors, with the recovery period varying depending on the extent and type of surgery.

• Chemotherapy: A systemic treatment with drugs designed to kill dividing cells, including cancer cells, but may come with significant side effects.

• Radiation Therapy: A treatment option that employs high-energy particles to target and destroy cancer cells while minimizing damage to surrounding healthy tissues.