dna structure for learners to understand better
TRANSCRIPT
• DNA molecules are polymers called polynucleotides.
• Each polynucleotide is made of monomers called nucleotides.
• Each nucleotide consists of :• a nitrogenous base (Adenine,
Thymine, Cytosine or Guanine) • a pentose sugar (DNA = Deoxyribose
sugar), • and a phosphate group.
• Nucleotide monomers are linked together to build a polynucleotide.
• Adjacent nucleotides are joined by covalent bonds that form between the –OH group on the 3’ carbon of one nucleotide and the phosphate on the 5’ carbon on the next nucleotide.
• These links create a backbone of sugar-phosphate units with nitrogenous bases as appendages.
• The sequence of bases along a DNA polymer is unique for each gene.
• THE ROLE OF DNA
• DNA is vital for all living beings – even plants.
• It is important for:• inheritance, • coding for proteins and • the genetic instruction
guide for life and its processes.
DNA holds the instructions for an organism's or each cell’s development and reproduction and ultimately death.
DNA can replicate itself.
NON-CODING DNA
Multicellular eukaryotes have many introns(non-coding DNA) within genes and noncodingDNA between genes.
The bulk of most eukaryotic genomes consists of noncodingDNA sequences, often described in the past as “junk DNA”
Much evidence indicates that noncoding DNA plays important roles in the cell.
Sequencing of the human genome reveals that 98.5% does not code for proteins, rRNAs, or tRNAs.
Recombinant DNA is used to make transgenic bacteria.
They are used to make insulin, clotting factor VIII, human growth hormone and hepatitis B vaccine.
Transgenic bacteria is used to protect the roots of plants from insect attack, by producing insect toxins.
• Example = pomato
• Genetically modified to produce potato's below the ground and tomato's above the ground.
• Foreign genes transferred to cotton, corn, and potato strains have made these plants resistant to pests because their cells now produce an insect toxin.
• Read p. 253 for more examples
Today transgenic bacteria, plants and animals are called genetically modified organisms (GMO’s).
The products that GMO’s produce are called biotechnology products.
• RNA is made up of:
• Ribose sugar (a pentose sugar with 5 carbons),
• Phosphate and
• A nitrogenous base; e.g. Purines(Adenine and Guanine) and Pyrimidines (Cytosine and Uracil).
• RNA exists largely as single nucleotide chains in living cells.
• The RNA strand is made up of alternating molecules of ribose sugar and phosphate.
• The nitrogen bases are attached to the sugar molecules in the strand and ’stick out’ laterally as in DNA.
• A sugar, a nitrogenous base and a phosphate together form a ribonucleotide.
• An RNA molecule is a polymer of ribonucleotides.
Williamson, J. 2014. powertpointslides. UJ
Campbell, & Reece. 2010. Biology. Benjamin Cumming. New York