DNA & Protein Synthesis

• The student will investigate and understand common mechanisms of inheritance and protein synthesis.

• Key concepts include:– f) the structure, function, and replication of

nucleic acids (DNA and RNA); and– g) events involved in the construction of

proteins.

• The student will investigate and understand common mechanisms of inheritance and protein synthesis.

• Key concepts include:– h) use, limitations, and misuse of genetic

information; and– i) exploration of the impact of DNA

technologies.

History

• Before the 1940’s scientists didn’t know what material caused inheritance.

• They suspected it was either DNA or proteins.

History

• A series of experiments proved that DNA was the genetic material responsible for inheritance.

History

• In 1952, Alfred Hershey and Martha Chase did an experiment using a virus that infects E. coli bacteria.

• The experiment proved that DNA and not protein is the factor that influences inheritance.

History

• Erwin Chargaff discovered the base pairing rules and ratios for different species.

• Adenine pairs with Thymine

• Cytosine pairs with Guanine.

History• Rosalind Franklin & Maurice Wilkins had

taken the 1st pictures of DNA using X-ray crystallization

This proved that DNA had a helical shape.

History• The Nobel Prize in Medicine 1962

Francis Harry Compton Crick

James Dewey Watson

Maurice Hugh Frederick Wilkins

Rosalind Franklin(Died of cancer 1958)

Wilkins has become a historical footnote and

Watson & Crick are remembered as the

Fathers of DNA

Watson Crick

DNADNA

OO=P-O O

PhosphatePhosphate GroupGroup

N

Nitrogenous baseNitrogenous base (A, T(A, T,, G, C)G, C)CH2

O

C1C4

C3 C2

5

SugarSugar(deoxyribose)(deoxyribose)

Nitrogen Bases

• 2 types of Nitrogen Bases– Purines

• Double ring–G & A

– Pyrimidines• Single ring

–C & U & T

PGA

CUT PY

DNA - double helixDNA - double helix

P

P

P

O

O

O

1

23

4

5

5

3

3

5

P

P

PO

O

O

1

2 3

4

5

5

3

5

3

G C

T A

T A

DNA

• The genetic code is a sequence of DNA nucleotides in the nucleus of cells.

DNA• DNA is a double-

stranded molecule.

• The strands are connected by complementary nucleotide pairs (A-T & C-G) like rungs on a ladder.

• The ladder twists to form a double helix.

DNA

• During S stage in interphase, DNA replicates itself.

• DNA replication is a semi-conservative process.

DNA• Semi-conservative

means that you conserve part of the original structure in the new one.

• You end up with 2 identical strands of DNA.

DNA

• Gene - a segment of DNA that codes for a protein, which in turn codes for a trait (skin tone, eye color, etc.)

• A gene is a stretch of DNA.

DNA

• A mistake in DNA replication is called a mutation.

• Many enzymes are involved in finding and repairing mistakes.

Mutations

• What causes mutations?– Can occur spontaneously– Can be caused by a mutagen

• Mutagen: An agent, such as a chemical, ultraviolet light, or a radioactive element, that can induce or increase the frequency of mutation in an organism.

Mutations

• Some mutations can:

• Have little to no effect

• Be beneficial (produce organisms that are

better suited to their environments)

• Be deleterious (harmful)

Mutations• Types of mutations

– Point Mutations or Substitutions: causes the replacement of a single base nucleotide with another nucleotide

• Missense- code for a different amino acid

• Nonsense- code for a stop, which can shorten the protein

• Silent- code for the same amino acid (AA)

Mutations

• Example: Sickle Cell Anemia

Mutations• Types of mutations

– Frame Shift Mutations: the number of nucleotides inserted or deleted is not a multiple of three, so that every codon beyond the point of insertion or deletion is read incorrectly during translation.

• Ex.: Crohn’s disease

Insertion Deletion

Mutations• Types of mutations

– Chromosomal Inversions: an entire section of DNA is reversed.

– Ex.: hemophilia,

a bleeding disorder

DNA Repair

• A complex system of enzymes, active in the G2 stage of interphase, serves as a back up to repair damaged DNA before it is dispersed into new cells during mitosis.

RNARNA

OO=P-O O

PhosphatePhosphate GroupGroup

N

Nitrogenous baseNitrogenous base (A, (A, UU ,, G, C )G, C )CH2

O

C1C4

C3 C2

5

SugarSugar (ribose)(ribose)

RNA

• Function: obtain information from DNA & synthesizes proteins

3 differences from DNA

1. Single strand instead of double strand

2. Ribose instead of deoxyribose

3. Uracil instead of thymine

3 types of RNA

1. Messenger RNA (mRNA)- copies information from DNA for protein synthesis

Codon- 3 base pairs that

code for a single amino

acid. codon

3 types of RNA

2. Transfer RNA (tRNA)- collects amino acids for protein synthesis

Anticodon-a sequence of 3 bases that are complementary base pairs to a codon in the mRNA

3 types of RNA

3. Ribosomal RNA (rRNA)- combines with proteins to form ribosomes

Amino Acids

• Amino acids- the building blocks of protein

• At least one kind of tRNA is present for each of the 20 amino acids used in protein synthesis.

Transcription - mRNA is made from DNA & goes to the ribosomeTranslation - Proteins are made from the message on the mRNA           

Transcription

• In order for cells to make proteins, the DNA code must be transcribed (copied) to mRNA.

• The mRNA carries the code from the nucleus to the ribosomes.

Translation

• At the ribosome, amino acids (AA) are linked together to form specific proteins.

• The amino acid sequence is directed by the mRNA molecule.

ribosome

Amino acids

Make A Protein

• DNA sequence

ATG AAA AAC AAG GTA TAG

• mRNA sequence

UAC UUU UUG UUC CAU AUC

Make mRNA

• mRNA sequence

UAC UUU UUG UUC CAU AUC

• tRNA sequenceAUG AAA AAC AAG GUA UAG

Make mRNA

• mRNA sequence

UAC UUU UUG UUC CAU AUC

• Amino Acid sequence(protein)

Tyr Phe Cys Phe His Ile

Human Genome Project

• The Human Genome Project is a

collaborative effort of scientists around the

world to map the entire gene sequence of

organisms.

• This information will be useful in detection,

prevention, and treatment of many genetic

diseases.

DNA Technologies

• DNA technologies allow scientists to identify, study, and modify genes.

• Forensic identification is an example of the application of DNA technology.

Gene Therapy• Gene therapy is a technique for correcting

defective genes responsible for disease development.

• Possible cures for:– diabetes– cardiovascular disease– cystic fibrosis– Alzheimer's– Parkinson’s– and many other diseases is possible.

Genetic Engineering

• The human manipulation of the genetic

material of a cell.

• Recombinant DNA- Genetically

engineered DNA prepared by splicing

genes from one species into the cells of

a different species. Such DNA becomes

part of the host's genetic makeup and is

replicated.

Genetic Engineering • Genetic engineering techniques are used in

a variety of industries, in agriculture, in

basic research, and in medicine.

This genetically engineered cow resists infections of the udders and can help to increase dairy production.

Genetic Engineering • There is great potential for the development

of useful products through genetic

engineering• EX., human growth hormone, insulin, and pest-

and disease-resistant fruits and vegetables

Seedless watermelons are genetically engineered

Genetic Engineering • We can now grow new body parts and soon

donating blood will be a thing of the past,

but will we go too far?

Photo of a mouse growing a "human ear"