DNA & Protein SynthesisSOL: BIO 6 f - i

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.

Protein Synthesis

• DNA codes for chains of amino acids that fold to form proteins.

• Your body is made up of protein structures:– Enzymes– Genes– Skin, hair, nails, etc.

Different from DNA replication

• DNA replication is to pass along genetic code to new cells– Uses only DNA

• Protein synthesis is the use of that DNA sequence/code to make amino acids proteins– DNA is converted into mRNA then tRNA– Transcription and translation

3 differences from DNA

1. Single strand instead of double strand

2. Ribose instead of deoxyribose

3. Uracil instead of thymine

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 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 mRNA

• DNA sequence

ATG AAA AAC AAG GTA TAG

• mRNA sequence

UAC UUU UUG UUC CAU AUC

Make tRNA

• mRNA sequence

UAC UUU UUG UUC CAU AUC

• tRNA sequenceAUG AAA AAC AAG GUA UAG

Make a protein

• mRNA sequence

AUG AAA AAC AAG GUA UAG

• Amino Acid sequence

met lys asn lys val stop

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"