Nucleic Acids

• Polymers 
• DNA, RNA
• Monomers are nucleotides

• Components joined by condensation reactions:
• Phosphate 
• Ester bond
• Pentose sugar
• Glycosidic bond
• Nitrogenous base

• A sugar w/ 5 carbon atoms
• Can either be ribose sugar in RNA or deoxyribose sugar in DNA

• Many nucleotides joined together
• A repeating sugar-phosphate backbone from which organic bases project
• Bond between phosphate and sugar is phoD- bond

• Cytosine
• Thymine
• Uracil (RNA)
• Adenine
• Guanine

A purine will only pair w/ a pyrimidine.

• Hydrogen bonds between pairs of organic bases
• In DNA, pairing is between adenine-thymine, guanine-cytosine
• In RNA, pairing is between adenine-uracil, guanine-cytosine

• The bases grouped into pyrimidines are:
• Smaller
• Have a single-ringed structure
• They are: thymine, uracil, cytosine

• The bases grouped into purines are:
• Larger
• Have a double-ringed structure
• They are: adenine, guanine

• In the nucleus
• 2 nucleotide strands:
• -> twisted into double helix
• -> linked by H-bonds between bases
• -> run antiparallel with 3' and 5' ends
• Sugar-phosphate backbone with deoxyribose sugar
• Bases: G, C, T, A
• Function: passes genetic info from cell to cell + gen to gen
• 3.2 bil base pairs = infinite variety of base sequences, providing genetic diversity

• Stable structure - passes from gen to gen w/out change, rarely mutates
• H-bonds - between strands, allows them to separate during replication/p. synthesis
• Large molecule - carries lots of genetic info
• Backbone - protects bases
• Base pairing - allows replication + mRNA

• Two strands of nucleotide
• Held together by hydrogen bonding
• Twisted around each other

• Found throughout cell
• 1 strands -> can be folded into diff shapes
• Pentose sugar: ribose
• Bases: G, C, U, A

The strands run in opposite directions.

• PhoD-backbone - protects bases inside helix from external forces
• Hydrogen bonds - link base pairs, forming bridges between strands
• -> 3 H-bonds are between C + G so the higher the proportion of C-G pairs, the more stable the DNA

• Purines are larger - ensures that polynucleotide strands are equally spaced apart
• The structure of DNA remains exact and regular - vital since
• DNA carries the heredity material for an individual
• DNA can exist as a very long sequence of bases - to carry the large amount of genetic information

• For mitosis/protein synthesis
• So daughter cells have genetic info to produce enzymes/proteins they need

When 2 new DNA are produced, one of the strands of each helix is from the original DNA and the other is new

The inheritance of DNA by daughter cells when a parent cell divides

• DNA: carries genetic info inherited from parent DNA
• mRNA: carries genetic info from nucleus to ribosomes where polypeptides are synthesised
• tRNA: binds to amino acids + carries them to mRNA combines w/ ribosomes

• Sections of DNA
• Control characteristics by coding for proteins through sequences of bases

The position of a gene on a chromosome

Different version of a gene

• Bases swap
• Order of bases changes -> sequence of amino acids changes -> different primary structure -> diff tertiary structure -> changes characteristics

• The 4 types of nucleotide
• Both strands of DNA molecule - act as template for attachment of nucleotides
• Helicase
• Polymerase
• Chemical energy

• Semi-conservative method
• DNA helicase breaks hydrogen bonds to separate strands
• Free nucleotides bind to complementary base pairs on template strands
• DNA polymerase joins nucleotides in condensation reactions, H-bonds and phoD-bonds form
• 2 identical DNA molecules are formed, each containing half the original DNA

• Polymerase joins the 2 strands together
• If inhibited, DNA molecules would not form
• DNA replication would slow/stop