RNA and Protein Synthesis

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) • 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 • 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”

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

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

snipped out snipped out Again... unit of transcription in a DNA strand exon intron exon intron exon transcription into pre-mRNA 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 baseson 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 andattaches 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 bondsand 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

RNA and Protein Synthesis