DNA, Genes And Chromosomes

• Describe Prokaryotic DNA

  DNA molecules are shorter

  DNA molecules are circular

  DNA is not associated with proteins.

  
  

  - NO CHROMOSOMES.

  
  

  - No true nucleus.
• Describe Eukaryotic DNA

  DNA molecules are very long

  DNA molecules are linear

  DNA molecules associated with histones

  
  

  - Highly coiled and folded.

  
  

  - Linear DNA associated with histone proteins to form chromosomes.
• Describe how a DNA molecule and its associated proteins form a chromosome

  DNA double helix is wound around histones to fix it in position ---> DNA-histone complex is then coiled ---> coil is then looped and further coiled before being packed into a chromosome ---> lots of DNA condensed into a single chromosome.
• Explain the DNA contain inside the mitochondria and chloroplasts of the eukaryotic cell

  Mitochondria and Chloroplasts of eukaryotic cells also contain DNA which is similar to prokaryotic DNA - short, circular and not associated with proteins.
• Define Gene

  A sequence of DNA bases that codes for a polypeptide or functional RNA
• Define Locus

  The fixed position of a specific gene on a chromosome
• Define allele

  Alternate versions of the same gene
• Define Codon (Triplet)

  = A sequence of three adjacent nucleotides (triplet) in mRNA that codes for one amino acid
• Define Degenerate

  = Most amino acids coded for by more than one triplet
• Define Universal

  = Each triplet codes for the same amino acids in all organisms
• Define Non-overlapping

  = Each base in the sequence only read once and is only involved in the codon for one amino acid.
• Explain why not all eukaryotic DNA codes for proteins?

  There are non-coding multiple repeats of base sequences between genes (VNTRs). Even within a gene, only some sequences (exons) actually code for amino acid sequences. These exons are separated by one or more non-coding sequences called introns.
• Define Exon

  = A segment of a DNA or RNA molecule containing information coding for a protein or peptide sequence.
• Define Intron

  = A segment of a DNA or RNA molecule which does not code for proteins and interrupts the sequence of genes.