In depth summarised notes on DNA - the code of life (nucleic acids) for matric (Grade 12) students according to the IEB syllabus with all necessary diagrams included. P.S the preview distorts the font and spacing so the document is more aesthetically pleasing once downloaded .
NUCLEIC ACIDS template for a complementary
- nucleic acids have capacity to new chain, i.e. each strand
store info that controls cellular could replicate
activity and the development - after the double helix model
of an entire system, do this by there were still questions
controlling synthesis of about how DNA directed the
proteins synthesis of proteins
- enzymes = proteins, control - in 1961, Francis Crick +
chemical processes inside Sydney Brenner provided
cells – ultimately control the genetic proof that a triplet
structure and functioning of all code was used in reading
living organisms genetic material in DNA and
transferring this info from the
Deoxyribonucleic acid (DNA) nucleus to the cytoplasm via
- at King’s College in London in RNA to where proteins are
early 1950s, Maurice Wilkins + made
Rosalind Franklin were trying - had shown that in DNA, form
to work out the structure of is function: double-stranded
DNA – took an experimental molecule could produce exact
approach, looking particularly copies of itself (replicate) and
at x-ray crystallography, i.e. carry genetic instructions, i.e.
diffraction images of DNA that the sequence of the
- at same time at Cavendish bases in DNA forms a code by
Institute at Cambridge which genetic info can be
University, Francis Crick + stored and transmitted
James Watson also became - of the DNA researchers, only
interested in determining the Rosalind Franklin had any
structure of DNA – analysed degrees in chemistry, worked
the x-ray data collected by mostly alone and suspected
Rosalind Franklin and others, through her x-ray diffractions
then built a model out of brass that all DNA molecules were
plates/clamps and realised helical in structure but was
that nucleic acids are reluctant to announce this
arranged like a twisted ladder finding until she had sufficient
w/ two runners made of evidence – died of cancer at
phosphates and sugars and a 37 before expressing her
series of rungs made of pairs views
of organic compounds known - in 1962 when Watson, Crick
as bases and Wilkins won the Nobel
- Watson and Crick developed Prize for physiology/medicine,
their ideas about genetic Franklin had already died –
replication Nobel can only be given to
- pairing of bases, i.e. A=T and living recipients and can only
C=G suggested that given a be shared among three
sequence of bases in one winners
strand, the other strand was Where is DNA found?
automatically determined – - mainly in nucleus of a cell
meant that when two strands where it forms an NB part of
separated, each served as a
1
, chromosomes that make up - as there are four diff
chromatin network nitrogenous bases, there are
- chromatin = chromosomal four diff nucleotides
material made up of DNA, RNA
and histone proteins as found
in a non-dividing cell
- DNA molecule is coiled so long
structures can fit in nucleus –
nearly two metres squeezed
into each human cell
- small amounts are found
outside nucleus in How is the double helix made
mitochondria in animals + up?
plants and in chloroplasts in - outer two strands of the
plants – called extranuclear or ladder are formed by a chain
extracellular DNA of alternating
sugar/phosphate links – bonds
between sugar and phosphate
molecules = strong
- rungs of the ladder are formed
How is DNA made up? from pairs of bases linked by
- two strands twist to form weak hydrogen bonds
stable, 3-dimensional double - base pairs are attached to
helix sugar molecules
How do the four base pairs
link up?
- shape/size of the four bases
What units make up DNA? differ so that:
- DNA molecule = long chain adenine will only bond w/
(polymer) made up of small thymine (or uracil in RNA)
units (monomers), i.e. building by means of two hydrogen
blocks called nucleotides bonds, e.g. A=T
- each nucleotide is made up of cytosine will only bond w/
a: guanine by means of three
sugar molecule – hydrogen bonds, e.g. C≡G
deoxyribose (S) How are base pairs classified?
phosphate molecule (P) - two groups = purines and
nitrogenous base which pyrimidines
may be: - base pairs always made of one
adenine (A) purine and one pyrimidine
thymine (T) - purines = two fused rings of
guanine (G) nitrogen, carbon and
cytosine (C) hydrogen atoms, e.g. guanine
- these four bases = foundation and adenine
of genetic code, instructing - pyrimidines = one ring of
cells on how to synthesise similar atoms and are
enzymes and other proteins therefore much smaller than
2
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