ZOOLFUN Q1

• allele: alternative forms of a gene for the same trait
• mendel: first person to formulate the principles of genetics
• incomplete dominance: An exception to Mendels law that states that no allele is completely dominant over the other.

  i.e. Red and white snapdragons produce pink, neither colors dominate
• Blending theory of inheritance is wherein both parents would blend their characteristics to the next generation.
• Codominance: both traits are expressed at the same time.

  Ex. Roan cattle
• Multiple Alleles:

  1. Many dissimilar alleles can exist in a population.
  2. Multiple Alleles arise through mutation at the same gene locus at different times.

  Ex. Human ABO blood roups
• Polygenic inheritance: An additive effect of two or more genes on a single phenotypic character.

  Ex. Skin pigmentation in humans is controlled by at least 3 separate inherited genes (A, B, C - Contributes one unit of darkness)

  
• Sex-Linked Inheritance:

  • Traits specified by genes located on sex chromosomes.
  • Designated as X-Linked or Y-Linked
  • X-Linked Traits: Most sex-linked traits are X-linked. Genes located on the X sex chromoesome
• Euploidy

  • addition or deletion of whole sets of chromosmes
  • polyploidy: Most common type of euploidy. Occurence of 3 or more sets of chromomes in an organism. More common in plants than animals.
• Aneuploidy

  • Usually caused by faillure of a pair of homologous chromomes to separate during meiosis (nondisjunction)
  • Monosomy: 1 less chromosome relative to the diploid parental number
  • Trisomy: 1 extra chromosome relative to the diploid parental number
• Trisomy 21 is Down syndrome, which is caused by an extra copy of chromosome 21

  
• Inversion: A change in chromosome structure wherein a Portion of a chromosome is reversed

  
• Deletion: A change in chromosome structure wherein the entire blocks of gene is lost.

  Ex. Cri du chat syndrome - "Cry of the cat"

  • Deletion in chromosome 5
  • Retarded
  • Small head with unusual facial deatures
  • Cry tahtsound like the meowing of the cat
• Translocation: A change of chromosome structure wherein nonhomologous chromosomes exchane sections.

  • Ex. Chronic myelgenous leukemia (CML): Portion of chromosomes 22 switch places with portion of chromsome 9
• Klinefelter syndrome - A human disorder due to the nondisjunction of sex chromosmes specifically the presence of an extra X chromosmes in male
• Males with extra Y chromosmes (XYY) - not characterized by any well defined syndrome but they tend to be taller than average.
• Females with trisomy X (XXX) - once in 1000 live births are healthy cannot be distinguisehd from XX females except by karyotype
• Cells: Basic Structural functional units of every organism
• Two Distinct types of cells: Prokaryotic and Eukaryotic Cell
• Rough Endoplasmic Reticulum

  Organelle studded by ribosomes and functions in protein synthesis
• Mitochondria :Site of cellular Respiration or ATP synthesis
• Plasma membrane

  outermost boundary of animals and is selectively permeable
• Cytoskeleton

  • Network of fibers that organizes structures and activities in the cell.
  • Organizes the cell's structures and activities, anchoring many organelles.
• Molecular structures of Cytoskeleton

  1. Microtubules - Thickest
  2. Microfilaments - Actin filaments, thinnest
  3. Intermediate filaments - fibers with diameters in a middle range
• Function of cytoskeleton

  • Support and Motility.
  • Helps to support the cell and maintain its shape
  • It interacts with motor proteins to produce motility
  • Inside the cell, vesicles can travel along tracks provided by the cytoskeleton

  
• Microtubules (Tubulin Polymers)

  • Hollow tubes
  • 25 mm with 15-mm lumen
  • Tubulin, a dimer consisting of alpha-tubulin and beta-tubulin
  • Maintenance of cell shape (compression-resisting "griders"); cell motility (cilia or flagella)
  • chromosome movements in cell division; organelle movements
• Microfilaments

  • Two intertwined strands of actin
  • 7 nm
  • Actin Maintenance of cell shape (tension-bearing elements); changes in cell shape; muscle contraction; cytoplasmic streaming in plant cells; cell motility (as in amoeboid movement); division of animal cells

  
• Intermediate filaments

  • Fibrous proteins coiled into cables
  • 8-12 nm
  • One of several different proteins (such as keratins) Maintenance of cell shape (tension-bearing elements); anchorage of nucleus and certain other organ-elles; formation of nuclear lamina

  
• Microtubules 


  Centrosomes and Centrioles

  • microtubules grow out from a centrosome near tenucleus
  • the centrosome has a pair of centrioles each with nine triplets of microtubules arranged in a ring.

  
• Microtubules (Cilia and Flagella)

  • Microtubules control the beating of flagella and cilia. microtubule containing extensions that project from some cells
  • Cilia and flagella differ in their beating patterns

  
• Cilia and flagella common structure

  • A core of microtubules sheathed by the plasma membrane
  • A basal body that anchors the cilium or flagellum
  • A motor protein called dynein, which drives the bending movements of a cilium or flagellum
  • 9x2 arrangement

  
• Microfilaments (Actin Filaments)

  • Microfilaments that function in cellular motility contain the protein myosin in addition to actin
  • In muscle cells, thousands of actin filaments are arranged parallel to one another
  • Localized contraction brought about by actin and myosin also drives amoeboid movement by extending pseudopodia

  
• Extracellular Matrix (ECM)

  • Animal cells lack cell walls but are covered by an elaborate ECM made up of glycoproteins such as collagen proteoglycans and fibronectin
  • ECM protects proteins bind to receptor proteins in the plasma membrane called integrins

  
• Cell Junctions


  Neighboring cells in tissues, organs, or organ systems often adhere, interact, and communicate through direct physical contact.

  
• Tight junctions


  Membranes of neighboring cells are pressed together preventing leakage of extracellular fluid
• Desmosomes 


  anchoring junctions that fasten cells together into strong sheets
• Gap junctions


  Communicating junctions that provide cytoplasmic channels between adjacent cells
• Mitosis and Cell Division

  
  

  All cells arise from the division of pre-existing cells.

  In most multicellular organisms, all cells originate from the zygote.

  • single cell resulting from union of an egg and a sperm (gametes)
• Cell division

  
  

  Division of the nucleus (karyokinesis)

  • Mitosis (somatic cells)
  • Meiosis (sex cells)

  Division of the cytoplasm (cytokinesis)
• Mitosis

  • Nuclear division associated with formation of somatic (body) cells
  • Produces daughter cells genetically identical to the mother cell
  • Important in growth and tissue repair in multicellular organisms
  • Method of transmitting genetic from parent to progeny in animals that reproduce asexually.