DNA

• DNA

  • Large complex molecule - the ‘template’ that codes for the production of proteins (e.g. hormones, enzymes) which are responsible for structure and function of cells
  • Double helix shape

   

  • Majority is located in the cells nucleus
  • Small amounts found in mitochondrion - mitochondrial DNA (mtDNA) - contains 37 genes
  • mtDNA is freely floating in the mitochondrial matrix and circular in shape

   

  • The DNA in one human cell is approx 2m long
  • For it to fit in the cell’s nucleus it must condense
  • The condensed DNA forms chromosomes
  • Have have 46 chromosomes in most cells of their body.

   
• Key terminology

  • Gene - a short region of DNA that codes for a specific protein, producing a specific trait (phenotype)
  • Chromosome - a structure containing coiled, condensed DNA it is only visible during cellular division
  • Somatic cells - Body cells. A full set of chromosomes
  • Gametes - sex cells. Half the chromosomes  
• Nucleotides (building blocks of DNA)

  • Consists of 1 phosphate, 1 pentode sugar molecule (deoxyribose sugar) + 1 nitrogenous base
• Nitrogen base pairs

  • Each “rung” of the DNA base is formed from 2 nitrogenous bases
  • 4 bases - adenine (A) + thymine (T). Cytosine (C} + guanine (G)
  • A + T are held together with 2 hydrogen bonds
  • C + G are held together with 3 hydrogen bonds
• Base pairing

  • These weak hydrogen bonds involved in base pairing between the complementary strands allow for its replication and for the production of proteins - protein synthesis
• Types of chromosomes

  • Autosomal chromosomes - first 22 homologous pairs of chromosomes.
  • Responsible for body cell characteristics
  • Sex chromosomes - 23rd pair
  • Individuals sex
  • XX female
  • XY male