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Protein Synthesis
Proteins
 Information in DNA is used to make
proteins
 Proteins determine traits (eye color, hair
color)
 Proteins are chains of amino acids
 20 different amino acids
 Combinations of amino acids determine a
proteins purpose
Protein Synthesis
 Proteins are assembled on
ribosomes which are in the
cytoplasm
 DNA can’t leave the nucleus
so the cell needs a way to get
DNA’s info to the ribosome
 RNA carries info from DNA to
the ribosomes and carries out
the process by which proteins
are made
 mRNA, tRNA, rRNA
Transcription
 First step of protein synthesis
 During transcription, a molecule of DNA is
copied into a complementary strand of
RNA
 Nucleotides (bases) are arranged in
groups of 3 – a codon – to form specific
“words”
 Ex: ATG, CAG, GGA
 64 possible words
Transcription = DNA → RNA
Steps of Transcription
1. DNA strands separate
2. Complementary bases of RNA are added
to the strand (much like DNA replication,
but T will be replaced with U because
RNA doesn’t have T)
mRNA (messenger RNA)
 The newly formed strand which will then
go to where thy will be translated.
 Ex: ATC GAC TAG CTA  DNA
 mRNA
Translation
 The mRNA from transcription will code for a
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particular amino acid.
During translation, the information is decoded
and arranged into amino acid sequences.
tRNA (transfer RNA) carries amino acids to the
ribosomes where they join together to form
proteins
rRNA (ribosomal RNA) is part of the structure of
ribosomes
mRNA is used to make tRNA  then codes for
amino acids
Codon Chart
 The codons of mRNA formed from
transcription are used to determine the
order of amino acids using the codon chart
Guided Practice
 EXAMPLE:
 DNA  ATG CAT GAC TTA
 RNA 
 AAS 