The Central Dogma: DNA, RNA, and Proteins

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Transcript The Central Dogma: DNA, RNA, and Proteins

The Central Dogma:
DNA, RNA, and
Written by Dallas Duncan and Dr. Frank B. Flanders
June 2010
What is DNA?
 DNA is short for
Deoxyribonucleic Acid
 DNA is comprised of genes,
which are the basic building
blocks of life
 DNA is made up of
nitrogenous bases – adenine,
guanine, cytosine, and
thymine – coiled into a double
helix structure
 Like fingerprints, everyone’s
DNA is different, varying only
by the order of the bases
What is RNA?
 RNA is short for
Ribonucleic Acid
 Very similar to DNA,
except it is single-stranded
and has the nitrogenous
base uracil instead of
 RNA is made from DNA,
and has many functions,
including helping to
manufacture proteins
 Examples of RNA include
tRNA, rRNA, and mRNA
What are Proteins?
 Proteins are nutrients
made of amino acids
arranged in a specific
 Proteins act as enzymes
to catalyze reactions,
help cells retain their
shapes, and act in cell
signaling and adhesion
 Necessary part of the
human and animal diet
Transcription: RNA Synthesis
 DNA unwinds in the nucleus
 RNA polymerase recognizes a specific sequence in the DNA, called a promoter, and binds
to it
 The promoter identifies the start of a gene, which strand should be copied, and what
direction it should be copied.
 Complementary bases are assembled between the new strand of mRNA and DNA
 At the five prime end of the mRNA strand, a cap is added, and a poly-adenine tail is
added to the other end.
 Introns, or regions of mRNA which don’t contain a genetic message, are removed
 Exons, or the remaining portions of mRNA once introns are removed, are put together to
form the mature mRNA transcript
 The mature mRNA
transcript moves
out of the nucleus
and into the
cytoplasm through
pores in the
nuclear membrane
Translation: Protein Synthesis
 A ribosome attaches to the
mRNA at a start codon.
 tRNA and amino acid complexes
bind to an mRNA codon after
forming base pairs with a tRNA
 The ribosome moves from
codon to codon along the
mRNA strand, adding amino
acids one by one, as called for
by the genetic code
 A release factor binds to the
stop codon, ending translation
and releasing the completed
protein from the ribosome