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Protein Synthesis
Modern Genetics: Protein Synthesis
DNA:
 Deoxyribose Nucleic Acid (from the nucleus)
 Discovered by Watson and Crick
 Genetic material replicates or doubles (during
mitosis or meiosis)
 The process where genetic info is passed from
generation to generation
 Controls cell activities through
enzymesprotein
 Provides codes or instructions for making
proteins
1. Structure of DNA
 Twisted ladder made of nucleotides
 Phosphate

Sugar – 5 carbon
Deoxyribose - DNA

nitrogen base
 Nitrogen Bases are:
1. Purines – double carbon ring
a. Adenine
b.Guanine
2. Pyrimidines – single carbon ring
a. Thymine
b.Cytosine
 Complimentary Base Paring between bases:
1. Adenine to Thymine (RNA has Uracil not
Thymine)
2. Guanine to Cytosine
3. Base pairs are bonded together by weak
hydrogen bonds
2. DNA replication
 DNA separates b/w nitrogen bases
 Hydrogen bonds are broken
 Each strand becomes a “template” where
replication occurs
 DNA replication results in two exact copies of
the cells DNA
1 is the original DNA strand the other is a
new strand
 Provides information to RNA for protein
synthesis
RNA
 Necessary for protein synthesis (proteins act as
enzymes which regulate the body
 Ribonucleic acid is different from DNA in
3 ways
1. RNA is Single stranded
2. RNA contains ribose not Deoxyribose
3. Instead of Thymine RNA uses Uracil to
pair with Adenine
1.RNA Transcription
 “reading” the code on a gene to create a
strand of RNA
 “start” signal or the promoter signal on the
gene begins the process of transcription
 RNA polymerase unwinds a section of the
double helix
 RNA floating in the nucleus binds to the
exposed base pairs on the strand of DNA.
 At the “stop signal, or terminal signal, the
sequence of RNA is complete
 Transcription results in a new
molecule/strand of RNA called messenger
RNA or mRNA
2.Messenger RNA:
 Made in the nucleus from DNA
 Carries instructions for making proteins to
ribosomes (site of protein synthesis)
 Ribosome “read” the mRNA
 Instructions on the mRNA are written as a
3 nucleotide sequence CGU
 This sequence is called a CODON
 The codon (3 nucleotide sequence) codes
for a specific amino acid, or signals to start (
begins at AUG of the mRNA) the
translation process or stop the process
(UAA, UAG, UGA)
3.Transfer RNA:
o tRNA (from the cytoplasm) carries an
amino acid on one end and has an
anticodon on the opposite end
o Anticodon – 3 nucleotide sequence that is
complimentary to the codon on the mRNA
o The complimentary tRNA binds to the
mRNA (at the ribosome) and an amino
acid is bonded to an adjacent a.a. with a
peptide bond.
o The process is repeated creating a chain of
amino acids
o the chain of a.a builds a specific
protein
The process of reading the mRNA to assemble
amino acids into
proteins is called: Translation.
Codons code for the following Amino Acids. The
chain of a.a represent a specific protein.
The whole process looks something like
this:
DNA  transcription RNA translation 
amino acids protein
One more Thing….
 During transcription:
 Transcribed genes produce: INTRONS and
EXONS on the strand of RNA
 Introns- DO NOT CODE FOR AMINO
ACIDS (proteins)
 Exons- codes for the amino acids (proteins)
 As RNA is being made, transcription, introns
are “taken out” and left in the nucleus later
stored in the nucleolus.

Exons are joined together to form a complete
functional strand of RNA, which then leave the
nucleus now called mRNA