RNA and Protein Synthesis

The Plan… How does DNA control cell activities if it can’t leave the nucleus? It sends a messenger! - messenger RNA (mRNA for short) Remember, DNA contains the code for making proteins. DNA can’t leave the nucleus, so RNA has to help out and actually make the proteins on the ribosomes.

 Ribonucleic Acid Ribonucleic acid (RNA) - molecule that controls the production of proteins for cells. A strand of RNA is made of repeating units (monomers) called nucleotides (like DNA) What makes up a nucleotide?

RNA vs. DNA Three differences between RNA and DNA: Single-stranded Ribose instead of Deoxyribose Uracil instead of Thymine

Checkpoint: RNA vs. DNA DNA RNA  Double strand Deoxyribose Contains Thymine Stays in nucleus Single Strand Ribose Contains Uracil Leaves nucleus

Types of RNA  Messenger RNA (mRNA) Transfer RNA (tRNA) single, uncoiled strand serves as pattern for assembly of amino acids Transfer RNA (tRNA) carries amino acids to the ribosome single stranded Ribosomal RNA (rRNA) globular form makes up the structure of the ribosome

Transcription  Process of making mRNA from a single–strand of DNA. The nitrogen bases in RNA always bond to their complement on the DNA strand ADENINE binds to URACIL GUANINE binds to CYTOSINE

Steps in Transcription  Steps in Transcription The enzyme RNA polymerase “unzips” the complementary strands of DNA into two single strands. RNA nucleotides bond to a single strand of DNA The finished mRNA is released and the two DNA strands “re-zip”

Steps in Transcription RNA DNA RNA polymerase Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) Transcription animation

mRNA Processing A U G G G C A U U A G C C U A  Enzymes remove (cut out) introns because they interrupt the coding sequence INTRONS INTERRUPT … INTRONS OUT !!! Exons are left behind to be “expressed” (translated) as needed proteins

unit of transcription in a DNA strand Again... unit of transcription in a DNA strand exon intron exon intron exon transcription into pre-mRNA snipped out snipped out mature mRNA transcript

Checkpoint!  Transcribe the DNA strand into RNA: TAC TCG TCC ATA GGC ATC AUG AGC UGG UAU CCG UAG

 Protein Synthesis Bases in mRNA code for the amino acids which will make a functioning protein. A group of three sequential bases on an mRNA strand is a CODON.

Lab – Part 1 Read the introduction and highlight 5 important facts Transcribe the two DNA sequences. Complete the Codon activity

 The Genetic Code There are a possible 64 CODONS that code for 20 AMINO ACIDS and a START/STOP SIGNAL. The genetic code is universal among all organisms.

The Genetic Code mRNA strand – G C A A C G U U G C U A C U G Amino Acids – Alanine - Threonine - Leucine - Leucine - Leucine -

 Steps in Translation Process of using RNA to assemble amino acids into proteins. mRNA moves out of the nucleus and attaches to ribosome. tRNA transports amino acids to the ribosome.

Steps in Translation

 Steps in Translation The anticodon on tRNA bonds to the complementary codon on mRNA. Amino acids form peptide bonds and form a strand – a polypeptide. The stop codon on mRNA ends the process and the new protein is released.

Steps in Translation Translation animation

Your Turn! Be A Ribosome … Translate your codons into amino acids: A U G C A U A G C C U A Met His Ser Leu Protein Synthesis Video

Lab – Part 2 Now it’s your turn to be RNA!

Concept Mapping for RNA Translation --------------------------Anti-codon Peptide bond ----------------------Amino Acids Uracil --------------------------------RNA Challenge: mRNA -----tRNA ------rRNA