Central DogmaProtein 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

Cytoplasm

Nucleus

DNA

DNA is the genetic material within the nucleus.

Central Dogma

RNA

Protein

Replication

The process of replication creates new copies of DNA.

TranscriptionThe process of transcription

creates an mRNA using

DNA information.

TranslationThe process of translation

creates a protein using

mRNA information.

Protein Synthesis

Transcription Translation

Transcription• The new RNA molecule is formed by

incorporating nucleotides that are complementary to the template strand.

DNA coding strand

DNA template strand

DNA

5’

3’

5’

3’

G T C A T T C G G

C A G T A A G C C

G

RNA

5’

GG U C A U U C

3’

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.

Transcription

Codon Codon Codon

Translation

DNA

T T C A G T C A G

DNAtemplatestrand

mRNA

A A G U C A G U C MessengerRNA

Protein Lysine Serine ValinePolypeptide(amino acidsequence)

Codon

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

Translation Termination

mRNA5’

CU

U

Met Gly CysLys

Stop codonRibosome reaches stop codon

C UG

Arg

U U U CG G G G GGA A A A A U A A

ReleasefactorP

A

Translation Termination

UU U

CG G G G G

GAA A A A U A A

C UG

MetGly

CysLys

Arg

Releasefactor

Once stop codon is reached, elements disassemble.

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•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.

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