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CYTOGENETICS
Lesson
[TRANS] LESSON 01: CELL ORGANIZATION
WHAT ARE CELLS?
● Basic unit of life ● Smallest thing that can make life ● All living things are composed of cells ● Much better off when it works with other organisms ● Vary in size ○ Bacterial cell (few micrometers) ○ 0.45 micrometer → smallest bacterial cell ○ Frog eggs → visible to naked eye; up to a mm ● Vary in shapes ○ Circular ○ Oblong ○ Spiral ○ Branching ○ Protozoa (perimysium) ○ Geometrical ○ Blob/irregular (macrophage) ● Vary in function ○ Chloroplasts → photosynthesis ○ Muscle cells → contraction ○ Macrophage → immune response ○ Unicellular organisms can function on their own ● Vary in living environments ○ Optimal ○ Harsh
SIMILARITIES IN ALL CELLS
MEMBRANE-ENCLOSED
● separated to environment by a layer in a protected environment
ABLE TO GROW AND DIVIDE
● binary fission in bacteria ● sexual reproduction (higher beings) ● Viruses can reproduce, but not without a host ○ Chemical zombies ○ Inert and inactive outside the body, malignant when it gains entry
FOLLOW THE CENTRAL DOGMA
● process by which DNA is transcribed to RNA which is then translated to protein
CONDUCT METABOLIC PROCESSES
● Anabolism- building up of compounds ● Catabolism- breaking down of molecules to simpler ones
UNDERGO EVOLUTION
● Mutation from ancestral cells ○ Mutations → corruption of DNA instruction ■ Worse - will eventually die ■ Better - better in survival and reproduction ■ Neutral - genetically different but equally viable ● Evolution → the process by which living things gradually modified and adapted to their environment in more and more sophisticated ways
THE 2 MAJOR CELL DIVISIONS
PROKARYOTES
● Prokaryotes → a jumble of materials inside ○ No true nucleus ○ Single celled life ○ Pro-karya = before nucleus ● Typically rodlike, spherical or corkscrew shaped ● Replicates itself in 20 mins under viable conditions ○ Forms chains, clusters ○ Most chemically diverse class of cells ● Has 2 domains
BACTERIA
● Most diverse group of cells on earth ● Have similar cell membranes ● Found in all habitats ● Some are clinically relevant to humans ○ more well studied ● Have nucleoids
ARCHAEA
● Similar to bacteria ● Different cell wall and plasma ● Found in harsh environments ○ underwater sea vents ○ Volcanic springs ● Poorly studied because we cannot replicate their harsh environments ● have nucleoids ● Don’t have membrane bound organelles, everything happens in cytoplasm
EUKARYOTES
● Has membranes/organelles ● True nucleus ○ Eu-karya = has nucleus ○ Single cell or multicellular ■ Single cell → yeast, amoeba ● May have originated as predators ○ Protozoans ■ Didinium
● Has 1 domain
EUKARYA
● Have nucleus ● Have membrane bound organelles ● More complex in structure than prokaryotes ● More evolved
EVOLUTIONARY RELATIONSHIP BETWEEN CELLS
● Believed that all organisms came from LUCA ○ Last universal common ancestor ● Archaea was first to diverge from LUCA ○ 3.5-3.8 billion years ago ● Eukarya then diverged from Archaea ○ 2 billion years ago ● Bacteria and archaea represent the bulk of our organisms here on Earth
ORGANELLES IN A CELL
● Separate, recognizable substructures of a cell with specific functions
NUCLEUS
● DNA is stored as chromosomes ● Information store of the cell ● Enclosed in a double membrane nuclear envelope ○ Less prone to mutation because it is enclosed and separated from other organelles
MITOCHONDRIA
● ATP generated thru cellular respiration ● Generate usable energy from food molecules ● Double membrane organelle ● Has DNA on its own ○ Replicates on its own ○ Inner membrane has folds for increased surface area
CHLOROPLAST
● Found in Plants and algae Photosynthetic bacterium ○ Cannot be found in fungi and animal cells ● There are Compartments instead of folds ● Double membrane ● Has own DNA ● Capture energy from the sun ○ Photosynthesis → trapping energy from the sun in chlorophyll to make energy-rich sugar molecules
ENDOSYMBIONT THEORY
● The mitochondria are prokaryotic cell engulfed by eukaryotic cell forming a symbiotic relationship
ENDOPLASMIC RETICULUM
● Single membrane organelle ● Maze of interconnected spaces ● Originate from outer membrane of nucleus ● Dotted with ribosomes ○ Smooth ER – source of cell membrane ○ Rough ER – makes proteins ● Primary site for cell membrane and extracellular protein production
MODEL ORGANISMS
● Organisms that represent a population because of similar DNA structure ● Reproduce rapidly ● Easily viewed ● Examples ○ Bacteria → E-coli ○ Saccharomyces cerevisiae yeast; fungi ■ Brewer’s yeast ○ Arabidopsis thaliana (plant) ■ Wall cress ○ Drosophila melanogaster (insect) ○ Caenorhabditis. elegans (worms) nematode; nonpathogenic ○ Zebrafish (fish; model vertebrate) ○ Lab mice (model mammal) ○ Humans
CELL CULTURES
● human cells that are extracted from humans and studied in lab ○ 2D ○ 3D
TAKEAWAYS
● Cells are the fundamental units of life. All present-day cells are believed to have evolved from an ancestral cell that existed more than 3 billion years ago. ● All cells are enclosed by a plasma membrane, which separates the inside of the cell from its environment. ● All cells contain DNA as a store of genetic information and use it to guide the synthesis of RNA molecules and proteins. This molecular relationship underlies cells’ ability to self-replicate. ● Cells in a multicellular organism, though they all contain the same DNA, can be very different because they turn on different sets of genes according to their developmental history and to signals they receive from their environment. ● Animal and plant cells are typically 5–20 μm in diameter and can be seen with a light microscope, which also reveals some of their internal components, including the larger organelles. ● The electron microscope reveals even the smallest organelles, but specimens require elaborate preparation and cannot be viewed while alive. ● Specific large molecules can be located in fixed or living cells by fluorescence microscopy. ● The simplest of present-day living cells are prokaryotes—bacteria and archaea: although they contain DNA, they lack a nucleus and most other organelles and probably resemble most closely the original ancestral cell. ● Different species of prokaryotes are diverse in their chemical capabilities and inhabit an amazingly wide range of habitats. ● Eukaryotic cells possess a nucleus and other organelles not found in prokaryotes. They probably evolved in a series of stages, including the acquisition of mitochondria by engulfment of aerobic bacteria and (for cells that carry out photosynthesis) the acquisition of chloroplasts by engulfment of photosynthetic bacteria. ● The nucleus contains the main genetic information of the eukaryotic organism, stored in very long DNA molecules. ● The cytoplasm of eukaryotic cells includes all of the cell’s contents outside the nucleus and contains a variety of membrane-enclosed organelles with specialized functions: mitochondria carry out the final oxidation of food molecules and produce ATP; the endoplasmic reticulum and the Golgi apparatus synthesize complex molecules for export from the cell and for insertion in cell membranes; lysosomes digest large molecules; in plant cells and other photosynthetic eukaryotes, chloroplasts perform photosynthesis. ● Outside the membrane-enclosed organelles in the cytoplasm is the cytosol, a highly concentrated mixture of large and small molecules that carry out many essential biochemical processes. ● The cytoskeleton is composed of protein filaments that extend throughout the cytoplasm and are responsible for cell shape and movement and for the transport of organelles and large molecular complexes from one intracellular location to another. ● Free-living, single-celled eukaryotic microorganisms are complex cells that, in some cases, can swim, mate, hunt, and devour other microorganisms. ● Animals, plants, and some fungi are multicellular organisms that consist of diverse eukaryotic cell types, all derived from a single fertilized egg cell; the number of such cells cooperating to form a large, multicellular organism such as a human runs into thousands of billions. ● Biologists have chosen a small number of model organisms to study intensely, including the bacterium E. coli, brewer’s yeast, a nematode worm, a fly, a small plant, a fish, mice, and humans themselves. ● The human genome has about 19,000 protein-coding genes, which is about five times as many as E. coli and about 5000 more than the fly Organelle Function Cytosol Contents of the main compartment of the cytoplasm, excluding membrane-enclosed organelles such as endoplasmic reticulum and mitochondria. The cell fraction remaining after membranes, cytoskeletal components, and other organelles have been removed cytoplasm Contents of a cell that are contained within its plasma membrane mitochondrion Membrane-enclosed organelle, about the size of a bacterium, carries out oxidative phosphorylation and produces most of the ATP in eukaryotic cells. nucleus In biology, it refers to the prominent, rounded structure that contains the DNA of a eukaryotic cell. In chemistry, refers to the dense, positively charged center of an atom chloroplast Specialized organelle in algae and plants that contains chlorophyll and serves as the site for photosynthesis lysosome Membrane-enclosed organelle that breaks down worn-out proteins and organelles and other waste materials, as well as molecules taken up by endocytosis; contains digestive enzymes that are typically most active at the acid pH found inside these organelles. chromosome long, threadlike structure composed of DNA and proteins that carries the genetic information of an organism; becomes visible as a distinct entity when a plant or animal cell prepares to divide Golgi body Membrane-enclosed organelle in eukaryotic cells that modifies the proteins and lipids made in the endoplasmic reticulum and sorts them for transport to other sites. peroxisome Small membrane-enclosed organelle that contains enzymes that degrade lipids and destroy toxins.
