nucleotides, DNA and RNA

• A Nucleotide consists of A pentose sugar, A nitrogenous base and a phosphate group.
• The Elements in a nucleotide are: Carbon, hydrogen, Oxygen, Nitrogen and Phosphorus.
• the four bases in DNA are: Adenine, Thymine, Cytosine and Guanine.
• The pentose sugar in DNA is deoxyribose.
• the pentose sugar in RNA is ribose.
• There are three types of RNA: Messenger RNA (mRNA), Transfer RNA (tRNA) and ribosomal RNA (rRNA).
• Adenine and Guanine have a double ring structure. They are 'purines'
• Thymine, Cytosine and Uracil have a single ring structure. They are 'pyrimidines'
• The bases in RNA are: Adenine, Uracil, Cyotsine and Guanine
• A bond can be formed between a phosphate group of one nucleotide and a hydroxyl group from carbon 3 of another nucleotides pentose sugar. This is a phosphodiester bond.
• DNA consists of two polynucleotide strands that run antiparallel. They form a double helix.
• Base pairs in DNA are: Adenine and Thymine, Guanine and Cytosine.
• The Base pair of Adenine and Thymine form two hydrogen bonds.
• The base pair of Cytosine and Guanine form three hydrogen bonds.
• RNA is a single stranded molecule of a polynucleotide chain.
• DNA is a very long molecule and is found in chromosomes.
• RNA is a relatively short molecule and is found in the cytoplasm.
• Everytime a cell undergoes division, all of its DNA is copied.
• First, the enzyme DNA Helicase attaches to the DNA molecule and breaks the hydrogen bonds between base pairs. Causing the two chains to separate.
• Next, free nucleotides line up with their complimentary base pairs on the separate polynucleotide strands but are only held in place by hydrogen bonds.
• The free nucleotides in DNA replication are called activated nucleotides and contain three phosphate groups.
• Next, DNA Polymerase attaches to the new strands and moves down the molecule catalysing the formation of phosphodiester bonds between the activated nucleotides. These nucleotides then lose their two extra phosphate groups, which are used to provide energy for the reaction.
• After the sugar-phosphate backbone is formed for the new strands, we have two copies of our double-stranded dna molecule. Each copy contains one strand from the original molecule and hence this process is semi-conservative.
• Sometimes an incorrect base is inserted in a growing polynucleotide. This is a mutation and can be very dangerous to an organism.
• Exons are apart of a polynucleotide strand which are coding that end up in a mRNA molecule.
• Introns are part of a polynucleotide strand that are non coding and end up in pre-mRNA before being removed.
• The enzyme DNA Gyrase untwists the double helix of a DNA molecule.
• The enzyme DNA ligase helps finalise the lagging strand by filling the gaps caused by okazaki fragments.
• Exonuclease removes the RNA primers from DNA strands so polymerase can come and continue the strand.
• topoisomerase stops the DNA that will be replicated from winding too far around histone proteins.
• Single stranded binding proteins hold apart the two strands of the DNA molecule, holding open the replication bubble.
• Point mutations are where one DNA base is replaced with another.
• Frame shift is the addition of a base to a base sequence of a DNA molecule meaning that codons would be read differently.
• A non-sense mutation is one where a stop codon is added prematurely, shortening the length of the mRNA molecule produced stopping the desired protein from being produced.
• A missense mutation causes an amino acid change in the sequencing of the protein primary structure, influencing how it will twist and fold.
• Silent mutations do not have a major impact on the final product.
• Conservative mutations produce a similar amino acid to the one required which can sometimes allow the synthesised protein to still function as desired.
• A non-conservative mutation produces a whole different type of amino acid in the protein structure, which largely effects the protein synthesised and its ability to function as desired.
• DNA primase is an enzyme which adds primers made of RNA along the polypeptide chain of DNA, providing a starting point for DNA polymerase to start moving along the molecule and building a new DNA strands.
• DNA primase adds RNA primers at the 3' end of a DNA strand.