DNA, genes and chromosomes

• What are the three components of nucleotides

  A pentose sugar, a phosphate group, an organic base
• Describe the structure of DNA

  ~Made up of a deoxyribose sugar, a phosphate group, and one of four organic bases

  ~It is double stranded, and hydrogen bonds between the bases form a helix shape
• Describe the role of DNA

  Carries genetic information and determines our inherited characteristics
• Describe the structure of RNA


  ~Made up of a ribose sugar, a phosphate group, and one of four organic bases

  ~It is single stranded
• Describe the role of RNA

  Transfers genetic information from DNA to ribosomes for protein synthesis
• How is DNA in eukaryotic cells different from in prokaryotic cells

  Eukaryotic cells = found in nucleus, long and linear. Associated with histone proteins to form chromosomes. Mitochondria and chloroplasts contain prokaryotic like DNA

  Prokaryotic cells = short and circular. Not associated with proteins
• What is the genetic code

  ~The order of bases on DNA

  ~Consists of codons
• Identify features of the genetic code

  Non overlapping = each triplet is only read once

  Degenerate = more than one triplet codes for the same amino acid

  Universal = same bases and sequences used by all species
• What is a gene

  ~A sequence of bases on a DNA molecule that codes for a specific sequence of amino acids to make polypeptide

  ~Can also code for functional RNA
• What is a locus 


  The fixed position on a DNA molecule occupied by a gene
• What is an allele


  Different versions of the same gene, found at the same locus on a chromosome
• What are axons and introns

  Axons = regions of DNA that code for amino acid sequences. Separated by one or more introns

  Introns = regions of DNA that do not code for anything
• Where are introns found

  ~Between axons

  ~Within genes