DNA
o Rosalind Wilkins devised that the DNA structure was helical
o James Watson and Francis Crick analysed the data collected by Rosalind
Franklin and they built a model showing the double helical
o DNA deoxyribonucleic acid
o Forms the chromosomes that make up chromatin in the nucleus
o In humans, each cell normally contains 23 pairs of chromosomes, for a total of 46.
Twenty-two of these pairs, called autosomes, look the same in both males and
females. The 23rd pair, the sex chromosomes, differ between males and females
o DEF: carries hereditary info that forms genes, codes for protein synthesis and
can replicate so copies of info are passed onto daughter cells
o A polymer (double helix ladder) made up of monomers called nucleotides
NUCLEOTIDE STRUCTURE
Each nucleotide has a sugar molecule
(deoxyribose), phosphate molecule and a
nitrogenous base which may be
thymine/adenine/guanine/cytosine
Nitrogenous bases pair with each other –
weak hydrogen bonds
AT – X2 BOND
GC – X3 BOND
Strong sugar phosphate bonds form
Many nucleotides = 1 gene
Thousands of genes could occur on one
DNA strand – length determines protein
o Rosalind Wilkins devised that the DNA structure was helical
o James Watson and Francis Crick analysed the data collected by Rosalind
Franklin and they built a model showing the double helical
o DNA deoxyribonucleic acid
o Forms the chromosomes that make up chromatin in the nucleus
o In humans, each cell normally contains 23 pairs of chromosomes, for a total of 46.
Twenty-two of these pairs, called autosomes, look the same in both males and
females. The 23rd pair, the sex chromosomes, differ between males and females
o DEF: carries hereditary info that forms genes, codes for protein synthesis and
can replicate so copies of info are passed onto daughter cells
o A polymer (double helix ladder) made up of monomers called nucleotides
NUCLEOTIDE STRUCTURE
Each nucleotide has a sugar molecule
(deoxyribose), phosphate molecule and a
nitrogenous base which may be
thymine/adenine/guanine/cytosine
Nitrogenous bases pair with each other –
weak hydrogen bonds
AT – X2 BOND
GC – X3 BOND
Strong sugar phosphate bonds form
Many nucleotides = 1 gene
Thousands of genes could occur on one
DNA strand – length determines protein
