RNA and Protein Synthesis

What is a gene? A region of DNA that contains instructions for the making of proteins. A region of DNA that contains instructions for the making of proteins.

chromosomes:  fibers of DNA (chromatin) and proteins enes  contains all genetic information for cell on genes genes contain information for synthesis of proteins DNA is blueprint for organization, development, daily functioning of cell.

RNA Ribonucleic acid Ribonucleic acid Function: moves the genetic information from DNA in the nucleus to the ribosome (site of protein synthesis) in the cytoplasm Function: moves the genetic information from DNA in the nucleus to the ribosome (site of protein synthesis) in the cytoplasm

RNA Structure Formed by nucleotides Sugar – Ribose Phosphate group Nitrogenous Base Adenine Uracil (replaces thymine) Cytosine Guanine Single-stranded

3 types of RNA Messenger RNA (mRNA) Messenger RNA (mRNA) Ribosomal RNA (rRNA) Ribosomal RNA (rRNA) Transfer RNA (tRNA) Transfer RNA (tRNA)

Messenger RNA (mRNA) Structure – single strand Structure – single strand Function – carries genetic information from DNA in nucleus to the ribosome Function – carries genetic information from DNA in nucleus to the ribosome Location - nucleus Location - nucleus

Rules of base-pairing apply for the mRNA DNA mRNA - A - T - G - C - T - A U - A - C - G - A - U - A always with U C always with G Making of the Mobile Messenger Piece of DNA that has information to make a specific protein RNA must be complementary “complementary” to DNA

Ribosomal RNA (rRNA) Structure – globular Structure – globular Function – makes up the ribosome Function – makes up the ribosome Location – ribosome Location – ribosome

rRNA = ribosomal RNA structural work-bench  ”structural work-bench” on which proteins are built

Transfer RNA (tRNA) Shape – hairpin (t-shaped) Shape – hairpin (t-shaped) Function – carries (transfers) amino acid to ribosome Function – carries (transfers) amino acid to ribosome Location – cytoplasm to ribosome Location – cytoplasm to ribosome

tRNA = transfer RNA tRNA = transfer RNA one specific amino acid 1. picks up one specific amino acid AND mRNA codon 2. pairs with mRNA codon specific for that amino acid only!

Protein Synthesis 2 stages 2 stages Transcription in the nucleus Transcription in the nucleus Translation in the ribosome Translation in the ribosome

Transcription + Translation: Nucleus RNAProtein Cytoplasm DNA TRANSCRIPTION TRANSLATION

Transcription Transferring information from DNA to mRNA Transferring information from DNA to mRNA

Codon 3 bases of mRNA nucleotides 3 bases of mRNA nucleotides Each codon codes for a specific amino acid Each codon codes for a specific amino acid Near universal – supports idea that organisms are related Near universal – supports idea that organisms are related

Codons Start Codon – AUG Start Codon – AUG Stop Codons – UAA, UAG, UGA Stop Codons – UAA, UAG, UGA These codons tell translation to begin and end These codons tell translation to begin and end

Anticodon 3 bases of tRNA nucleotides 3 bases of tRNA nucleotides Complementary to mRNA codon Complementary to mRNA codon Located on opposite end of amino acid Located on opposite end of amino acid

Ribosome Composed of rRNA with 3 binding sites Composed of rRNA with 3 binding sites Free in cytoplasm – proteins are used in the cell Free in cytoplasm – proteins are used in the cell RER – makes proteins to be exported out of the cell RER – makes proteins to be exported out of the cell

DNA vs. RNA DNA 5 Carbon Sugar = Deoxyribose 5 Carbon Sugar = Deoxyribose Base Pairs = Adenine Base Pairs = Adenine Thymine Thymine Guanine Guanine Cytocine Cytocine Original copy of genetic information Original copy of genetic information RNA 5 Carbon Sugar = Ribose Base Pairs = Adenine Uracil Guanine Cytocine Disposable copy of genetic information

ribosome “reads” mRNA codons one at a time

mRNAcodons mRNA codons... C G C A A G C C C U G U protein protein = G C G arginine lysine U U C proline G G G cysteine A C A ANTICODONS

How About An Example? DNA: TGG CCA ATA mRNA: ACC GGU UAU tRNA: UGG CCA AUA ACC= 20 GGU=12 UAU=13 Code for an Amino Acid Sequence! Example = Hairy

Steps for Translation: 1. mRNA leaves nucleus to cytoplasm - codons specify certain AA sequence 2. mRNA associates with ribosome which “reads” mRNA codons one at a time synthesis of proteins occur on ribosomes 3. tRNA with specific amino acid (corresponding to anticodon) carries correct amino acid to mRNA + ribosomes 4. tRNA delivers correct amino acid (anticodon-codon base pairing) to ribosome and leaves 5. polypeptide elongates in sequence directed by the mRNA codons  formation of peptide bond between amino acids 6. termination reached at stop codon  ribosome falls off  polypeptide is released

Transcription Exons – coding regions of DNA Exons – coding regions of DNA Introns – non-coding regions of DNA Introns – non-coding regions of DNA Cut out (spliced) which controls the genetic information that leaves the nucleus Cut out (spliced) which controls the genetic information that leaves the nucleus