DNA, RNA, and Protein
Central Dogma
DNA → RNA → Protein
(Transcription)
(Translation)
Steps from DNA to Proteins
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There are three steps involved in making ALL
proteins.
1st – The DNA must be replicated
2nd – The DNA must be transcribed. This means
the DNA must be made into RNA
3rd- The RNA must be translated. This means the
RNA must be made into proteins.
Transcription
After DNA has been replicated, the DNA must be
transcribed.
 Transcription is DNA being converted into RNA.
Why?
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DNA codes for many messages, but DNA
not leave the nucleus.
can
It must be made
into RNA to leave the nucleus.
RNA
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RNA – Ribonucleic Acid
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Single stranded
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Contains a ribsose sugar, a nitrogenous base,
and a phosphate group.
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What kind of sugar did DNA have???
Three Classes of RNAs
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Messenger RNA (mRNA)
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Ribosomal RNA (rRNA)
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Carries protein-building instruction
Major component of ribosomes
Transfer RNA (tRNA)
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Delivers amino acids to ribosomes
Base Pairing During
Transcription
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A new RNA strand can be put together on a DNA
region according to base-pairing rules
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As in DNA, C pairs with G
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Uracil (U) pairs with adenine (A)
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THERE IS NO THYMINE IN RNA!!!!!! It is
replaced by Uracil.
Transcription & DNA
Replication
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Like DNA replication
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Nucleotides added in 5’ to 3’ direction
Unlike DNA replication
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RNA polymerase catalyzes nucleotide addition
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Product is a single strand of RNA
Transcription
RNA polymerase, an enzyme, will unzip the DNA
 The new RNA strand will be complementary to
the unzip part of the DNA.
 It will follow the base pairing rule! Recall
different for RNA!
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The product from transcription is
mRNA
The mRNA will release and go to the cytoplasm
where ribosomes are located
So How is the Message
Translated?
Genetic Code
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Set of 64 base triplets – ex: AGA CCC
Codons - Nucleotide bases read in blocks of three
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61 of the base triplets specify amino acids
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3 stop codons – UGA, UAA, UAG
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There is 1 start codon – it also codes for the amino
acid methionine- AUG
Codon
Codon
Codon
Codon
Genetic Code
Genetic Code
Translation
Translations- “making Proteins” Translating
language of nucleic acids (base sequences) into
language of proteins (amino acids)
What are the subunits of proteins? Amino Acids
 There are 20 amino acids.
 Proteins are made on ribosomes; therefore,
Translation will occur on a ribsome.
 Recall – Where can ribsomes be found in a cell?
Inside the nucleus OR in the cytoplasm
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Translation
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Again, How is it transcribed?
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Occurring in the nucleus, where
transcription occurs to make mRNA, mRNA
will travel outside the nucleus to a ribosome.
Translation
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- During translation, the tRNA will come and
attach to the codon regions on the mRNA.
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tRNA has a sequence of bases, called the
anticodon. tRNA is also carrying the amino
acid.
anticodon
Codon
Once the tRNA anticodon has attached to the
mRNA codon, the appropriate amino acid will
be released.
 Now, the next codon will be read and the tRNA
will release appropriate amino acid.
 That amino acid will link with the previous
amino acids.
 These chains of amino acids will build a
polypeptide chain which will create a specific
protein.
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Polypeptide chain (protein) grows until ribosome
reaches stop codon
Protein molecule
stop codon
How bases are held together
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Nitrogenous bases are held together by hydrogen
bonds, the weakest type of bonds.
Scientist use genetic information to identify
people because it is unique to each person.
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The sequence of DNA nucleotides in cells is what
makes individuals unique from each other.