Genetics

• DNA replication is the process of producing identical DNA molecules (replication) from a single original DNA molecule.
• a dominant allele is expressed even if paired with a recessive allele
• a recessive allele is only expressed when it is not paired with a dominant allele
• the genotype refers to an individual's genetic makeup, while phenotype refers to their observable characteristics
• genotype is Bb and a phenotype is the percentage chance of getting the trait
• Homozygous is the same type of allele e.g BB or bb
• Heterozygous is when a dominant gene is paired with a recessive E.G Bb
• Homozygous dominant BB
• Homozygous recessive is bb
• The invention of the lens

  Robert Hooke (1665):  observed a thin slice of cork (dead plant cells) with a microscope.  He described what he observed as “little boxes” (cells).
• Discovery of Cells •Anton van Leeuwenhoek (1675): was the first person to observe living cells.
• Two types of cells

  •Eukaryotes: cells that contain a nucleus and membrane-bound organelles• •Prokaryotes: cells that lack nuclei and membrane-bound organelles••Nucleus: contains DNA which directs the activity of the cell•Organelle: a cell component that performs specific functions in the cell
• •Each living cell carries out the tasks of taking food, transforming food into energy, getting rid of waste, and reproducing.•Most eukaryotic cells have three main components:•Cell Membrane•Cytoskeleton•Nucleus

  
• •Cell Membrane •Structure: phospholipid bilayer with proteins that function as channels, markers, and receptors•Function: selectively permeable boundary between the cell and     the external    environment
• cell wall •Structure: rigid wall made up of cellulose, proteins, and carbohydrates•Function: boundary around the plant cell outside of the cell membrane that provides structure and support
• Neuclus •Structure: the nucleus is a sphere that contains another sphere called a nucleolus•Function:

      storage centre of cell’s    DNA,    manages cell functions
• Cytoplasm •Structure: gelatin-like fluid that lies inside the cell membrane•Function: -contains salts, minerals and organic molecules

    -surrounds the organelles
• CytoSkeleton Structure: a network of thin, fibrous elements made up of microtubules (hollow tubes)

  function: -acts as a support system for organelles-maintains cell shape
• Ribosomes

  •Structure: consist of two subunits made of protein and RNA

  •Function: protein synthesis
• Endoplasmic Reticulum

  •Structure: a system of membranous tubules and sacs

  •Function: intercellular highway (a path along which molecules move from one part of the cell to another)

  •Two types:•Rough Endoplasmic Reticulum

  •Smooth Endoplasmic Reticulum
• Rough Endoplasmic Reticulum

  •Rough Endoplasmic Reticulum (rER): prominent in cells that make large amounts of proteins to be exported from the cell or inserted into the cell membrane

  •Covered with ribosomes
• Smooth Endoplasmic Reticulum

  •Smooth Endoplasmic Reticulum (sER): involved in the synthesis of lipids and breakdown of toxic substances

  •Not covered with ribosomes
• Golgi Apparatus

  •Structure: stacked flat sacs

  •Function: receives proteins from the ER and distributes them to other organelles or out of the cell

  
  

  (receiving, processing, packaging, and shipping)
• Lysosomes

  •Structure: spherical organelles that contain hydrolytic enzymes within single membranes

  •Function: breaks down food particles, invading objects, or worn out cell parts
• Vacuoles

  •Structure: a sac of fluid surrounded by a membrane•Very large in plants

  •Function: used for temporary storage of wastes, nutrients, and water
• Mitochondria

  •Structure: folded membrane within an outer membrane

  •The folds of the inner membrane are called cristae

  •Function: converts energy stored in food into usable energy for work•cellular respiration
• Centrioles

  •Structure: composed of nine sets of triplet microtubules arranged in a ring

  •Exist in pairs

  •Function: centrioles play a major role in cell division (mitosis)
• Chloroplast

  •Structure: Contains chlorophyl which makes plants green


  •Function: carry out photosynthesis
• Levels of Structural Organization

  Atom 

  Molecule 

  Cell 

  Tissue 

  Organ 

  Organ System 

  Organism 
• phosphate

  pentose sugar

  nitrogenous base

  
• Adenine (A) + Thymine (T)

  Cytosine (C) + Guanine (G)
• DNA replication:

  The process by which DNA makes a copy of itself during cell division. 
• Replication

  Step 1

  The strands of the double

  helix separate in an unzipping motion.

  The bases are then exposed.
• Replication

  Step 2

  Free (unattached) nucleotides pair up with the exposed bases following the rules of complementary base pairing
• Replication

  Step 3

  Sugar and phosphate molecules bond with neighboring nucleotides and new strands of DNA are formed
• DNA

  2 identical “sister”      chromatids attached at an area in the middle called a centromere

  chromatids separate and 1 goes to each new cell

  When cells divide, “sister”

  
• Why does DNA need to change from a chromatin to a chromosome?

  more efficient division

  A) chromatin

  B) duplicates itself

  C) coils into a chromosome

  
• How many chromosomes do humans have?

  Human = 46 chromosomes or 23 pairs
• What cells have all the chromosomes?s

  •All somatic (body) cells in an organism have the same kind and number of chromosomes
• Why do cells devide?

  Growth

  repaire

  reproduction