1.2

• Replication


  The doubling of chromosomes resulting from the copying of DNA to produce chromatids before mitosis
• Complementary base pair


  The specific way DNA bases pair with each other (A-T, G-C)
• Genetic code


  The order of bases in a DNA molecule that determines an organism's characteristics
• Primer


  A short strand of nucleotides
• DNA polymerase


  An enzyme which is involved in DNA replication
• 5' end


  The phosphate end of a DNA strand
• 3' end


  The deoxyribose end of a DNA strand
• The two strands of DNA are antiparallel which means that one strand runs from 5' to 3' direction and the other strand runs from 3 to 5'. This creates the double-helix structure of DNA
• The base sequence of DNA forms the genetic code
• Nucleotides


  The basic unit of DNA
• Components of a nucleotide

  • Phosphate
  • Deoxyribose sugar
  • Base
• DNA bases


  • Adenine
  • Thymine
  • Cytosine
  • Guanine
• Complementary base pairs


  • Adenine pairs with Thymine (A-T)
  • Cytosine pairs with Guanine (C-G)
• Sugar-phosphate backbone


  Nucleotides are linked together to form strands by strong bonds between the deoxyribose sugar of one nucleotide to the phosphate of the next nucleotide
• DNA replication


  1. DNA molecule is unwound and unzipped

  2. DNA is replicated by DNA polymerase

  3. Two new strands twist to form a double-stranded helix
• Leading strand


  Synthesised continuously by DNA polymerase adding nucleotides to the deoxyribose 3' end in a 5' to 3' direction
• Lagging strand


  Synthesised in fragments by DNA polymerase as nucleotides cannot be added to the phosphate (5') end
• Polymerase chain reaction (PCR)


  A technique for amplification of DNA in-vitro using complementary primers for specific target sequences
• PCR process


  1. DNA is heated to separate strands

  2. Complementary primers bind to target sequences

  3. Heat-tolerant DNA polymerase replicates the region of DNA

  4. Repeated cycles of heating and cooling amplify the target region of DNA
• Compare


  Identify similarities and differences between two or more factors, using comparative words
• Sample


  A small, quantitative analysis of a larger group
• Reliable


  Randomised results which have been repeated several times to produce results which can be trusted or which you can have confidence in