Biology SL - Topic 1

Brightfield Microscopy

A type of light microscopy where the specimen is illuminated directly, often requiring staining for better visualization.

Cell Specialization

The process by which generic cells develop into specific types with unique functions.

Cell Theory

The principle that all living organisms are composed of cells, the cell is the basic unit of life, and cells arise from pre-existing cells.

Cell Wall

A rigid structure surrounding the cells of plants, fungi, and some prokaryotes, providing support and protection.

Chloroplast

An organelle in plants and some protists where photosynthesis occurs.

Compartmentalization

The division of the cell into distinct regions (organelles) to optimize efficiency and maintain specific environments for reactions.

Condenser

A lens system in a microscope that focuses light onto the specimen to improve illumination.

Contrast

The ability to distinguish differences in intensity or color between structures in a specimen, enhanced by staining or phase contrast.

Cytoplasm

The gel-like substance within the plasma membrane that contains organelles and is the site of many cellular processes.

Cytoskeleton

A network of protein filaments that provides structural support, aids in intracellular transport, and enables cell movement.

Darkfield Microscopy

A technique in which the specimen appears bright against a dark background, useful for observing unstained, living specimens.

Differentiation

The process by which a stem cell develops into a specialized cell with a specific function.

Endoplasmic Reticulum (ER)

A network of membranes involved in protein (rough ER) and lipid synthesis (smooth ER).

Ethics of Stem Cell Research

The moral considerations related to the use of embryonic stem cells and their implications for society.

Field of Vision

The observable area visible through the microscope eyepiece at a specific magnification.

Fluorescence Microscopy

A technique that uses fluorescent dyes to label specific molecules in a specimen, viewed under specific wavelengths of light.

Freeze-Fracture Cryogenic Electron Microscopy

A technique used to visualize the internal structures of membranes by freezing and fracturing the specimen.

Golgi Apparatus

An organelle responsible for modifying, sorting, and packaging proteins and lipids for secretion or delivery to other organelles.

Light Microscopy

A technique that uses visible light to magnify small structures, typically up to 1000x magnification.

Lysosome

A vesicle containing digestive enzymes to break down cellular waste and macromolecules.

Magnification

The degree to which the size of an image is larger than the object itself.

Microscopy

The use of microscopes to observe structures too small to be seen by the naked eye.

Mitochondrion

The powerhouse of the cell, where aerobic respiration and energy (ATP) production occur.

Multipotent Stem Cell

A stem cell that can differentiate into a limited range of cell types within a particular tissue or organ.

Nuclear Envelope

The double membrane surrounding the nucleus, containing pores to regulate molecule exchange.

Nuclear Envelope

The double membrane surrounding the nucleus, containing pores to regulate molecule exchange.

Nucleoid Region

The area in a prokaryotic cell where the DNA is located, not enclosed by a membrane.

Nucleus

The organelle that houses DNA and controls cellular activities.

Organ

A structure composed of multiple tissues working together to perform specific biological functions.

Organelle

A specialized subunit within a cell with a specific function, usually membrane-bound.

Peroxisome

A small organelle involved in lipid metabolism and the detoxification of harmful substances.

Phase-Contrast Microscopy

A technique that enhances contrast in transparent specimens, such as live cells, without staining.

Plasma Membrane

The selectively permeable membrane surrounding the cell, composed of a phospholipid bilayer.

Pluripotent Stem Cell

A type of stem cell that can differentiate into almost any cell type in the body.

Prokaryotic Cell

A cell without a nucleus or other membrane-bound organelles.

Prokaryotic Features

Includes a cell wall, plasma membrane, cytoplasm, nucleoid region, ribosomes, and sometimes a flagellum or pili.

Regenerative Medicine

A field of medicine focused on repairing or replacing damaged tissues using stem cells or tissue engineering.

Resolution

The ability of a microscope to distinguish two close points as separate.

Ribosome

A small structure that synthesizes proteins, found free in the cytoplasm or attached to the rough ER.

Scanning Electron Microscopy (SEM)

A type of electron microscopy that provides detailed three-dimensional-like images of the surface of a specimen.

Stem Cell

An undifferentiated cell capable of dividing and differentiating into various specialized cell types.

TEM (Transmission Electron Microscopy)

A type of electron microscopy that provides high-resolution images of internal structures.

Tissue

A group of similar cells working together to perform a specific function.

Totipotent Stem Cell

A type of stem cell that can differentiate into all cell types, including embryonic and placental cells.

Vesicle

A small membrane-bound sac that transports substances within or between cells.

Eukaryotic Cell

A cell with a nucleus and membrane-bound organelles.

Allele

One specific form of a gene, differing from other alleles by one or a few bases and occupying the same gene locus.

Anaphase

The stage of mitosis in which sister chromatids are separated and pulled to opposite poles of the cell by the spindle fibres.

Astral Microtubules

A subset of spindle microtubules that extend from the centrosomes toward the cell cortex, helping to position and anchor the spindle apparatus.

Autosome

Any chromosome that is not a sex chromosome (i.e., not X or Y).

Binary Fission

A method of asexual reproduction in prokaryotes where the cell replicates its DNA and divides into two genetically identical daughter cells.

Budding

A form of asexual reproduction where a new organism develops as an outgrowth or "bud" from the parent organism.

Cancer

A disease resulting from uncontrolled cell division leading to the formation of a tumour (neoplasm) that can invade surrounding tissue.

Carrier

An individual who has a recessive allele for a genetic trait or disorder but does not express the phenotype (typically used in the context of X-linked or recessive disorders).

Cell Cycle

The ordered sequence of events from when a cell is formed until it divides, consisting of interphase (G1, S, G2) and the mitotic phase.

Cell Division

The process by which a parent cell divides into two or more daughter cells, encompassing both nuclear division (mitosis or meiosis) and cytokinesis.

Cell Plate

The structure that forms during cytokinesis in plant cells, made of vesicles from the Golgi apparatus, which fuses to create a new cell wall separating the daughter cells.

Centromere

The region of a chromosome where the two sister chromatids are joined and where spindle fibres attach during cell division.

Chromatid

One of the two identical copies of a replicated chromosome, joined at the centromere.

Chromatin

The complex of DNA and histone proteins that makes up eukaryotic chromosomes in a non-dividing cell.

Chromosome

A structure made of DNA and proteins that carries genetic information in the form of genes; visible as distinct structures during cell division.

Cleavage Furrow

The indentation of the cell's surface that begins during cytokinesis in animal cells, caused by the contraction of a ring of actin and myosin filaments.

Clone

A group of genetically identical cells or organisms derived from a single parent through asexual reproduction or artificial techniques.

Codominance

An inheritance pattern where both alleles in a heterozygous individual are fully expressed in the phenotype (e.g., AB blood type).

Conformational Change

A change in the three-dimensional shape of a protein (e.g., a pump or receptor) often induced by binding a molecule like ATP , which is essential for its function.

Crossing Over

The exchange of genetic material between non-sister chromatids of homologous chromosomes during prophase I of meiosis, resulting in genetic recombination.

Cytokinesis

The division of the cytoplasm following mitosis or meiosis to form two (or more) separate daughter cells.

Diploid (2n)

A cell or nucleus containing two complete sets of chromosomes, one from each parent.

Dominant Allele

An allele that has the same effect on the phenotype whether in the homozygous or heterozygous state.

F1-generation (First Fillial)

The first generation of offspring produced from a cross of the P-generation.

Gamete

A haploid sex cell (sperm or egg) produced by meiosis that fuses with another during fertilization.

Genotype

The alleles of an organism carried for a particular characteristic.

Haploid (n)

A cell or nucleus containing a single set of unpaired chromosomes (e.g., gametes).

Histones

Positively charged proteins around which DNA is tightly wrapped to form nucleosomes, the basic unit of chromatin.

Homologous Chromosomes

A pair of chromosomes, one maternal and one paternal, that are the same length, have the same gene loci, and pair during meiosis.

Incomplete Dominance

An inheritance pattern where the heterozygous phenotype is an intermediate blend of the two homozygous phenotypes (e.g., pink flowers from red and white parents).

Interphase

The longest phase of the cell cycle, consisting of G1 (growth), S (DNA synthesis), and G2 (preparation for division); DNA is replicated here.

Kinetochore

A protein structure assembled on the centromere of a chromatid to which spindle microtubules attach during cell division.

Locus (plural: Loci)

The specific position of a gene on a chromosome.

Meiosis

A type of nuclear division that reduces the chromosome number by half, producing four genetically non-identical haploid nuclei from one diploid cell.

Metaphase

The stage of mitosis where chromosomes align at the cell's equator (metaphase plate).

Mitosis

A type of nuclear division that produces two genetically identical diploid daughter nuclei from one parent nucleus, for growth and tissue repair.

Monohybrid Cross

A genetic cross that investigates the inheritance of a single characteristic (one gene).

Motor Proteins

Proteins (e.g., kinesin, dynein) that use ATP to move along cytoskeletal filaments; they are crucial for chromosome movement during mitosis and meiosis.

Mutation

A permanent change in the base sequence of DNA; the original source of genetic variation.

Oncogene

A mutated gene that has the potential to cause cancer, often involved in promoting cell division.

Oogenesis

The process of egg (ovum) formation in the ovaries through meiosis, resulting in one large haploid ovum and up to three polar bodies.

P-generation (Parental)

The true-breeding parents used in the first cross of a genetic breeding experiment.

Pedigree Chart

A diagram that shows the occurrence and appearance of phenotypes of a particular gene or organism and its ancestors across generations, used to analyze inheritance patterns.

Phenological

Relating to the study of cyclic and seasonal natural phenomena, especially in relation to climate, plant, and animal life.

Phenotype

The observable characteristics of an organism, resulting from the interaction of its genotype with the environment.

Phenotypic Plasticity

The ability of an organism with a given genotype to change its phenotype in response to environmental changes.

Prophase

The first stage of mitosis where chromosomes condense, the nuclear envelope breaks down, and the spindle begins to form.

Punnett Grid

A diagram used to predict the genotypes and phenotypes of offspring from a genetic cross.

Random Orientation (Independent Assortment)

The random arrangement of homologous chromosome pairs (bivalents) on the metaphase plate during metaphase I of meiosis.

Recessive Allele

An allele that only has an effect on the phenotype when present in the homozygous state.

Reduction Division

A term for meiosis I, where the chromosome number is reduced from diploid (2n) to haploid (n) as homologous chromosomes are separated.

Segregation

The separation of alleles of a gene pair from each other during gamete formation (meiosis), so each gamete carries only one allele for each gene.

Sex Chromosome

A chromosome (X or Y in humans) involved in determining the biological sex of an organism.

Single Nucleotide Polymorphism (SNP)

A variation at a single base-pair position in a DNA sequence among individuals; the most common type of genetic variation.