FINAL EXAM BIO

• DNA


  Deoxyribonucleic acid, one of the two types of nucleic acids (the other is RNA)
• Main function of DNA

  To store an organism's genetic information
• Where DNA is found

  • Cell nucleus
  • Mitochondria
  • Chloroplasts (plants only)
• Nucleotide


  Repeating subunit of a nucleic acid, made up of a phosphate group, a 5-carbon sugar, and one of four nitrogenous bases
• Double helix


  The twisted ladder shaped molecule formed when nucleotides come together in a repeating pattern
• Chromatin


  DNA in its un-condensed form
• Chromosomes


  The condensed form of DNA, typically visible when the cell is preparing for or undergoing cell division
• Histones


  Proteins that DNA wraps around to coil into chromosomes
• Humans have 23 pairs of chromosomes
• Contributors to the discovery of DNA structure

  • Rosalind Franklin
  • James Watson
  • Francis Crick
• Base pair rule


  Adenine only bonds with Thymine, Guanine only bonds with Cytosine
• Chargaff's rule: DNA from any organism should have a 1:1 ratio of purine and pyrimidine bases, so %A=%T and %G=%C
• Percentages of nitrogen bases from DNA samples

  • Human: %A=30.0, %T=30.0, %G=20.0, %C=20.0
  • Chicken: %A=28.0, %C=22.0
  • Rat: %A=28.5, %G=21.5
  • E. coli: %G=26.0, %C=26.0
• Gene


  Segments of DNA that code for a protein
• Humans have ~20,000 genes
• DNA replication


  The process by which DNA copies itself before cell division
• There are approximately 3 billion base pairs in the human genome
• Semiconservative replication


  Each new DNA molecule contains one parent strand and one new, complementary strand
• Replication bubbles


  Sites along a DNA strand where the two halves have been split apart so each half can be copied
• DNA is synthesized only in the 5' to 3' direction
• DNA Helicase


  Enzyme that unwinds and unzips the DNA double helix
• DNA Polymerase


  Enzyme that adds nucleotides to the new DNA strand
• Mutation


  Any change in the original sequence of DNA base pairs
• Types of point mutations

  • Substitution: one letter replaces another
  • Insertion: one base is added
  • Deletion: one base is removed
• RNA


  Single-stranded nucleic acid that contains the bases adenine, guanine, cytosine, and uracil
• RNA uses DNA as a template and bonds to it with uracil instead of thymine
• Protein synthesis


  DNA → mRNA → protein
• Transcription


  The process of using DNA as a template to create a strand of messenger RNA (mRNA)
• Translation


  The process of using the mRNA code to direct the synthesis of a protein at a ribosome
• Codon


  A three base sequence on mRNA that codes for a particular amino acid
• Anticodon


  The three base sequence on tRNA that is complementary to the codon on mRNA
• As cells get larger, the volume increases faster than the surface area, so cells divide to maintain their metabolic needs
• Reasons cells divide


  • Growth
  • Repair or replacement of cells
  • Cancer (uncontrolled division of abnormal cells)
• Most mammalian cells divide in 12-24 hours, some bacterial cells divide in 20-30 minutes
• Apoptosis


  Programmed cell death that occurs after a cell has completed a certain number of divisions
• Childhood


  Cell division > cell death
• Adulthood


  Cell division = cell death
• Later years


  Cell division < cell death
• Interphase


  The stage of the cell cycle involving cellular growth and DNA replication
• Mitotic phase


  The stage of the cell cycle involving cell division