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RNA
Higher Human Biology
• Genotype = genetic constitution
• Phenotype = physical and chemical state
• The phenotype is determined by the proteins
synthesised when the genes are expressed
Structure of RNA
• Ribose Sugar, base, phosphate
• Uracil is the complementary base partner of
Thymine
• One strand
Types of RNA
• Messenger RNA (mRNA) – formed during
transcription of DNA in the nucleus and is the
template for protein synthesis at the
ribosomes
• Transfer RNA (tRNA) – carries specific amino
acids to the ribosomes for translation of the
genetic code
• Ribosomal RNA (rRNA) – binds to proteins to
form ribosomes
Proteins
• Polypeptide chains
• Subunits called amino acids
• Structure and function of protein depend on
sequence of amino acids
• This is controlled by the sequence of bases on
the DNA
Genetic Code
• The sequence of bases along a DNA strand are
grouped into triplets
• Each amino acid in a protein is coded for by
one or more of these triplets.
Gene Expression
• Genetic code is carried on DNA in the nucleus
of the cell
• Assembly of amino acids into polypeptides
happens in the cytoplasm
• Ribosomes
Protein synthesis
• A molecule of mRNA (messenger RNA) is
transcribed in the nucleus
• It leaves the nucleus via a pore in the nuclear
membrane
• Carries the information to ribosomes
• The mRNA meets tRNA (transfer RNA) and the
information is translated into a protein.
By the end of the lesson
• Draw a labeled diagram of a strand of RNA in
your jotters
• Cope the diagram at the foot of page 34
• Make a note of the 3 differences between
RNA and DNA
• Complete glossaries up until mRNA