DNA, RNA & PROTEINSDNA, RNA & PROTEINSPart 1Part 1

The molecules of life

• DNA provides the instructions for an organisms structure and characteristics

• DNA can be copied to make new cells that are identical to the original cell (Replication)

• Roles of DNA: Store, Copy and Transmit Information

• RNA (Nucleic Acid used for making protein)– Transcription– Translation

• Protein synthesis– Amino acids

DNADNA• Deoxyribonucleic Acid (DNA) is the

blueprint for life: contains ALL the necessary information to make a new organism

DNA structure• DNA is a polymer of

nucleotides– Each nucleotide composed of

• a phosphatephosphate, • a sugar (deoxyribose), • and organic nitrogenous base.

Four DNA bases• Four kinds of nitrogenous bases:

Purine basesA = AdenineG = Guanine

Pyrimidine basesT = ThymineC = Cytosine

DNA: Complimentary base pairing• Adenine pairs with Thymine

A T

• Cytosine pairs with Guanine

C G

Each DNA strand is a compliment of the other

Original strand Matching copy A TC GG CT AA TG CG CT AT A

DNA STRUCTURE

• DNA is a double helix • Discovered by

Watson and Crick, 1953

DNA structure

Antiparallel Strands

DNA REPLICATION (in the nucleus)

• Each DNA strand becomes a template, parent strand becomes apart

• Proper base-pairs areassembled on that template(with proper enzymes:polymerase and ligase).

• There’s always a pool of nucleotides (A,C,T,G) in the nucleus

Semi-Conservative Replication½ of the original is “conserved” and the other half is “new”

RNA structure and synthesis• RNA: Ribonucleic Acid• Is very similar to DNA

(repeating subunits, nucleotides).

• Difference between RNA and DNA:– Each nucleotide contains a different sugar

(ribose instead of deoxyribose)– Bases are A, G, C, and U (uracil, not thymine)

A pairs with U; G pairs with C

RNA

• RNA is single stranded and shorter

• RNA is less stable than DNA: RNA doesn’t persist in the cell for long (sometimes it exists for a few seconds), whereas DNA can persist for the life of the cell.

Protein Synthesis

DNARNA

Proteins

• 3 different RNA molecules involved in protein synthesis:– Messenger RNA (mRNA)– Ribosomal RNA (rRNA)– Transfer RNA (tRNA)

transcription

translation