Central Dogma

1
Central Dogma

• Protein Synthesis

2
Two types of nucleic acids
of strands
kind of sugar
bases used
3
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

4
Central Dogma
5
Protein Synthesis
Transcription
Translation
6
Transcription

• The new RNA molecule is formed by incorporating
  nucleotides that are complementary to the
  template strand.

DNA
DNA coding strand
5
G
T
C
A
T
T
C
G
G
3
3
C
A
G
T
A
A
G
C
C
5
DNA template strand
7
Where to Begin
8
Transcription
Production of mRNA copy of the DNA gene
9
Translation

• The process of reading the RNA sequence of an
  mRNA and creating the amino acid sequence of a
  protein is called translation.

10
(No Transcript)
11
Codon

• Translation will always begin with a start codon
  AUG (Start) and end with the TAG (end)

12
(No Transcript)
13
Translation Termination
Ribosome reaches stop codon
14
Translation Termination
Once stop codon is reached, elements disassemble.
Release factor
15
(No Transcript)
16
Who am I?
Messenger RNA
a.k.a. mRNA Copied from DNA, conveys information
from chromosomes to ribosomes. Every three
nucleotides is a codon.
17
Who am I?
Transfer RNA
a.k.a. tRNA Transports amino acids to ribosomes.
18
Who am I?
Ribosomal RNA
a.k.a. rRNA Subunits where the protein is
assembled
19
Translation
Synthesis of proteins by ribosomes
20
(No Transcript)
21
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.

22
Protein Synthesis General Pathway
23
Prokaryotes vs Eukaryotes Protein Synthesis

• Prokaryotes
• In prokaryotes, mRNA transcripts of a coding
  sequence are copied from the DNA as a single
  contiguous sequence.

• Eukaryotes
• The initial RNA transcript, while in the nucleus,
  is composed of exons, and introns.
• Before leaving the nucleus, introns are removed
  and splice exons together.
• 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.

24
(No Transcript)
25
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.

26
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.

27

• 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.

28
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.

29
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.

30
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?

31
Structure of DNA

• DNA Base Pairing Rules
• A T
• C G