Biological diversity – biodiversity – is reflected in the vast number of species of organisms, in the
variation of individual characteristics within a single species and in the variation of cell types within
a single multicellular organism.
Differences between species reflect genetic differe...
● Both DNA and RNA carry information
● DNA holds genetic information
● RNA then transfers genetic information from DNA to ribosomes
○ made of RNA and proteins
● Both DNA and RNA are polymers of nucleotides which consist of
○ pentose
○ 5 carbon sugar
○ nitrogen-containing organic base and phosphate group
● Components of DNA
○ deoxyribose
○ phosphate group
○ one organic base
■ adenine
■ cytosine
■ guanine
■ thymine
■ A+G double ring structures
■ purine bases
● Components of RNA
○ ribose
○ phosphate
○ one organic base
■ adenine
■ cytosine
■ guanine
■ uracil
■ T+U+C single ring structure
■ pyrimidines
In prokaryotic cells,
● DNA molecules are
○ short
○ circular
○ not associated with proteins.
, In the nucleus of eukaryotic cells,
● DNA molecules are
○ very long
○ linear
○ associated with proteins
■ called histones.
● Together a DNA molecule and its associated proteins form a chromosome.
○ chromosomes visible at the start of cell division
■ result of being tightly coiled around the histones
● Mitochondria and chloroplasts contains DNA
The mitochondria and chloroplasts of eukaryotic cells
● also contain DNA which, like the DNA of prokaryotes,
○ is short
○ circular
○ not associated with protein.
A gene is a base sequence of DNA that codes for:
● • the amino acid sequence of a polypeptide
● • a functional RNA (including ribosomal RNA and tRNAs).
● A gene occupies a fixed position, called a locus, on a particular DNA molecule.
A sequence of three DNA bases, called a triplet, codes for a specific
amino acid. The genetic code is universal, non-overlapping and
degenerate.
● each triplet known as a codon
● amino acids joined together by peptide bonds and form a polypeptide chain
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