Transcript Central Dogma - We Heart Science

Central Dogma
Protein Synthesis
Two types of nucleic acids
# of strands
kind of sugar
bases used
The Importance of Protein Synthesis
Specific Roles:
• Enzyme action
• Transport
• Motion
• Protection
• Support
• Communication
• Regulation
Examples:
•Protein antibodies for
immune system
•Hair, nails, skin
•Hemoglobin in blood
•Insulin to regulate blood
sugar levels
Central Dogma
DNA is the genetic material
within the nucleus.
Replication
The process of replication
creates new copies of DNA.
The process of transcription
creates an mRNA using
DNA information.
DNA
Transcription
RNA
Nucleus
The process of translation
creates a protein using
mRNA information.
Translation
Protein
Cytoplasm
Protein Synthesis
Transcription
Translation
Transcription
• The new RNA molecule is formed by
incorporating nucleotides that are
complementary to the template strand.
DNA coding strand
5’
3’
DNA
G T C A T T C G G
3’
G U C A U U C G G
3’
C A G T A A G C C
5’
DNA template strand
5’
RNA
Where to Begin
Transcription
Production of mRNA copy of the DNA gene
Translation
•The process of reading the RNA sequence of an mRNA
and creating the amino acid sequence of a protein is
called translation.
DNA
template
DNA
Transcription
T
T
C
A
G
T
C
A
G
A
A
G
U
C
A
G
U
C
strand
Messenger
RNA
mRNA
Codon
Codon
Codon
Translation
Protein
Lysine
Serine
Valine
Polypeptide
(amino acid
sequence)
Codon
•Translation will
always begin with a
start codon “AUG”
(Start) and end with
the “TAG” (end)
Translation Termination
Stop codon
Ribosome reaches stop codon
5’
mRNA
A U G G G A U G U A A G C G A U A A
P
Release
factor
A
Translation Termination
Once stop codon is reached,
elements disassemble.
Release
factor
P
A
Who am I?
Messenger RNA
a.k.a. mRNA
Copied from DNA, conveys information from
chromosomes to ribosomes. Every three
nucleotides is a codon.
Who am I?
Transfer RNA
a.k.a. tRNA
Transports amino acids
to ribosomes.
Who am I?
Ribosomal RNA
a.k.a. rRNA
Subunits where the
protein is assembled
Translation
Synthesis of proteins by ribosomes
Genes
• Genes: a set of instructions encoded in the
DNA sequence of each organism that specify
the sequence of amino acids in proteins
characteristic of that organism.
In eukaryotes, many general are
interrupted by introns and exons.
• Introns – long segments of nucleotides that
have no coding information.
• Exons – are the portions of a gene that are
translated (expressed) into proteins.
Protein Synthesis General Pathway
Prokaryotes vs Eukaryotes Protein Synthesis
Prokaryotes
Eukaryotes
•In prokaryotes, mRNA •The initial RNA transcript,
in the nucleus, is
transcripts of a coding while
composed of exons, and
sequence are copied
introns.
from the DNA as a
•Before leaving the nucleus,
introns are removed and splice
single contiguous
exons together.
sequence.
•The processed transcript,
then properly called mRNA and
carrying the appropriate codon
sequence for a protein, is
transported from the nucleus
to the ribosome for translation.
Tay-Sachs
• A baby with Tay-Sachs disease appears
healthy at birth. Symptoms usually first
appear 3 to 6 months after birth,
beginning with mild motor weakness
and occasional twitches of the eye
(myoclonic jerks). By 6 to 10 months of
age, the baby's motor skills may be lost.
After this, the diseases progresses
rapidly to seizures, blindness, paralysis,
and death at age 4 to 5.
Mutations
• Mutations are permanent changes in the
sequence of nitrogen-containing bases in
DNA.
• Mutations occur when base pairs are
incorrectly matched (e.g., A bonded to C
rather than A bonded to T) and can, but
usually do not, improve the product coded by
the gene.
• Inserting or deleting base pairs in an existing
gene can cause a mutation by changing the
codon reading frame used by a ribosome.
• Mutations that occur in somatic, or
nongerm, cells are often not detected
because they cannot be passed on to
offspring. They may, however, give rise to
cancer or other undesirable cellular changes.
• Mutations in the germline can produce
functionally different proteins that cause such
genetic diseases as Tay-Sachs, sickle cell
anemia, and Duchenne muscular dystrophy.
Duchenne muscular dystrophy
• In individuals with the disorder, initial
findings may include an unusual,
waddling manner of walking (gait);
difficulty climbing stairs or rising from a
sitting position; and repeated falling.
Duchenne muscular dystrophy
If it gets worse more
problems can occur like
• Progressive curvature of the
spine
• Wasting of thigh muscles and
abnormal enlargement of the
calves
• Abnormal fixation of certain
joints (joint contractures) due
to muscle weakness
• Prolonged immobility
• Shortening of muscle fibers
• By approximately age 10 to
12, most affected individuals
require the use of a
wheelchair.
Warm-Up
• The DNA in each of your cells are exactly
alike. How come so many of your cells
look completely different?
• Now talk to the person sitting next to
you and see what they came up with.
• What does trans mean?
• What does scribe mean?
• What would transcribe mean?
Structure of DNA
•DNA Base Pairing
Rules
•A
T
•C
G