DNA

Cards (52)

  • Receive a chemical signal to divide by mitosis, but some will simply live out their days
  • The cell cycle is controlled by checkpoints

    A cell may continue or stop based on chemical messengers in the cell
  • Checkpoints
    • Checkpoint 1-checking for nutrients, growth factors and DNA damage
    • Checkpoint 2-checking for DNA replication and cell size
    • Checkpoint 3- Metaphase checkpoint-checking to see if spindle fibers have attached properly (next lesson)
  • If a cell receives the correct chemical signal at a checkpoint, the cell continues forward in the cell cycle
  • Contact Inhibition (density-dependent inhibition)
    Crowded cells stop dividing when they touch other cells
  • Anchorage Dependence

    To divide, the cell must be attached to a substratum (i.e. extracellular matrix of a tissue)
  • Cancer cells do not exhibit the normal contact inhibition (which allows for tumors to form) nor do cancer cells exhibit anchorage dependence (which allows for metastasis)
  • The structure of DNA consists of two strands twisted around each other, forming a double helix.
  • X chromosome
    Genes on the X chromosome are different from the genes on the Y chromosome
  • Normal (human) body cell
    Has 46 chromosomes and is called a somatic cell
  • Somatic cell

    Diploid (two sets of chromosomes or 23x2)
  • Specialized cells that can undergo meiosis
    Can produce gamete cells, these are sperm and egg cells
  • Gametes
    Have 23 chromosomes - one copy of each
  • Gamete cell

    Haploid (one set of chromosomes or 23x1)
  • Genome
    The collection of chromosomes within a cell
  • Different species have a different number of chromosomes in their diploid cells, however the concept of diploid, haploid, somatic and gamete remains the same
  • Autosomes are chromosomes 1-22
  • Sex chromosomes are X and Y
  • There are 22 autosome chromosomes
  • Translation process of building a protein
    1. tRNA brings amino acids to the ribosome
    2. One at a time in the correct sequence dictated by the mRNA
  • Translation
    Part 2 of protein synthesis, using the mRNA as a template to build a protein
  • Translation: part 2
    1. Occurs at the ribosome in the cytoplasm
    2. Initiation: mRNA-patty attaches to small ribosomal subunit, start tRNA attaches to P site, large ribosomal subunit attaches
    3. Elongation: Aminoacyl tRNA synthase helps tRNA pick up amino acid, tRNA with amino acid lands at A site, P site tRNA releases amino acid to attach to A site amino acid, ribosome moves along mRNA one codon at a time, E site is where 'naked' tRNA goes before leaving
    4. Termination: Protein building continues until stop codon or releasing factor is reached, mRNA and protein are released, ribosome separates into subunits
  • The process in the ribosome builds the polypeptide chains that will become proteins
  • Transcription: part 1
    1. Occurs in the nucleus
    2. Initiation: RNA polymerase locates the start of a gene, attaches to DNA promoter (TATA box) sequence
    3. Elongation: RNA polymerase unwinds and unzips the DNA gene, attaches RNA nucleotides to the 3' end of the RNA
    4. Termination: RNA polymerase reaches the termination sequence AATAAA, releases from the DNA and the newly formed mRNA strand
  • Transcription
    Part 1 of protein synthesis, makes a complementary copy of a single DNA gene called mRNA
  • To process the mRNA strand: a) a guanine cap is added to the 5' end, b) a polyadenine tail (poly-A tail) is added to the 3' end, c) RNA splicing occurs - introns (non functional nucleotides) are removed and the remaining exons are joined together
  • Protein synthesis occurs in two parts: 1) transcription, 2) translation
  • Proteins are made of hundreds of amino acids joined together, and different proteins are created by joining the amino acids in different sequences
  • Protein synthesis is used by the cell to produce proteins
  • Each strand is made up of nucleotides that are linked together by phosphodiester bonds between adjacent sugar molecules.
  • Protein synthesis
    The control of protein synthesis
  • Gene expression is the control of protein synthesis
  • Gene regulation can occur three ways
  • Transcriptional Regulation
    Regulates when and how much mRNA can be produced
  • Translational Regulation
    Regulates how often the mRNA can be used
  • Post-transcriptional & post-translational regulation

    RNA and proteins can be degraded by methylation and phosphorylation to control how much active protein is created
  • Prokaryotic cells typically use transcriptional regulation
  • Cells save energy and resources by regulating which genes are used to create proteins at which time
  • Genes produce proteins, many proteins are enzymes which allow chemical reactions to occur
  • Most chemical reactions are actually metabolic pathways, meaning they are a series of chemical reactions each requiring their own enzyme