Introduction to Parkinson's Science/DNA
What is DNA?
[edit | edit source]DNA is an abbreviation of DeoxyriboNucleic Acid and is the name given to a string of proteins which provides the hereditary material contained within cells.
DNA is made up of 4 base compounds called ‘nucleotides’, viz:-
• Adenine (A) paired with Thymine (U)
• Guanine (G) paired with Cytosine (C)
• Cytosine (C) paired with Guanine (G)
• Thymine (U) paired with Adenine (A)
Nucleotides are aggregated into sets of three termed 'codons'. This gives 64 possible triplet combinations, but certain combinations give rise to the same shaped molecular structures so that functionally there is a limited set of amino acid structures.
These are:-
| AMINO ACID | ABBREVIATION | LETTER | COMBINATIONS |
| Alanine | Ala | A | GCU GCC GCA GCG |
| Aspartic acid | Asp | D | GAU GAC |
| Cysteine | Cys | C | UGU UGC |
| Glutamic acid | Glu | E | GAA GAG |
| Glutamine | Gla | Q | CAA CAG |
| Glycine | Gly | G | GGU GGC GGA GGG |
| Histidine | His | H | CAU CAC |
| Isoleucine | Ile | I | AUU AUA |
| Leucineine | Leu | L | UUA UUG CUU CUC CUA CUG |
| Lycine | Lys | K | AAA AAG |
| Methioninine | Met | M | AUG |
| Phenylalanine | Phe | F | UUU UUC |
| Proline | Pro | P | CCU CCC CCA CCG |
| Serine | HSer | S | UCU UCC UCA UCG AGU AGC |
| Threonine | Thr | T | ACU ACC ACA AGG |
| Tryptophan | Trp | W | UGG |
| Tyrosine | Tyr | Y | UAU UAC |
| Valine | Val | V | GUU GUC GUA GUG |
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DNA has been likened to a recipe book for proteins and each recipe is termed a ‘gene’.
How is DNA structured?
[edit | edit source]Amino acids are aggregated into linear strings. The strings consist of genes separated by intergenic material so that the genes occur at intervals along a string like pearls on a necklace, viz:-
GENE - - -INTERGENIC---GENE---INTERGENIC—--GENE and so on.
Intergenic material has sometimes been designated (erroneously)- as ‘junk DNA.
A gene consists of a Start codon, followed by a sequence of amino acids and then a Stop codon.
The most commonly occurring Start codon is AUG (Methionine)
The most commonly occurring Stop codons are:- UAA UAG UGA.
Mutations occur when DNA material is copied and one of the nucleotides in a codon (generally the third one) is accidentally changed.
What are chromosomes?
[edit | edit source]Organisms may have several gene strings called chromosomes’ the number of chromosome varies from species to species. A human being has 46 chromosomes, an earthworm has 36, the Adder’s Tongue Fern has about 1,200.
Further Reading and Viewing
[edit | edit source]Images for DNA
DNA Handbook
http://ghr.nlm.nih.gov/handbook/basics/dna
Interactive teaching site.(DNA)
Animated primer