Transcription & Translation Biology 6(C)

Learning Objectives Describe how DNA is used to make protein Explain process of transcription Explain process of translation Transcription and Translation

DNA (deoxyribonucleic acid) Stores genetic code Made of nucleotides Nucleotides – building blocks of DNA Phosphate group Deoxyribose sugar Nitrogenous base DNA – Our Genetic Code

DNA is the genetic material of organisms Master blueprint for all protein synthesis – Order of bases affects protein made What do proteins do? – Enzymes – Cell signaling – Structural Purpose of DNA

How does a molecule create a protein? 1.Copy of DNA made (transcription) 2.Copy modified and leaves nucleus 3.Copy used to create amino acid chain (translation) 4.Amino acid chain folds into protein From DNA to Protein

DNA Stored in nucleus Deoxyribose sugar Double-stranded Four bases – Adenine – Thymine – Cytosine – Guanine RNA Used in cytoplasm Ribose sugar Single-stranded Four bases – Adenine – Uracil – Cytosine – Guanine DNA and RNA

Transcription – process by which a portion of DNA nucleotide sequence is used to produce a complementary mRNA (messenger RNA) strand RNA polymerase – protein that initiates and operates transcription 1.Binds to promoter section of DNA 2.Separates DNA strands 3.Builds mRNA strand using one DNA strand as a template 4.Releases mRNA strand at stop signal Transcription

RNA Polymerase Non-template DNA strand Template DNA strand RNA nucleotides mRNA strand

A portion of DNA is shown below. What is the correct sequence of the resulting mRNA transcript if the top DNA strand is used as the template in transcription? Writing mRNA Sequences A G T A G G C A C T G C T C A T C C G T G A C G template DNA non-template DNA U C A U C C G U G A C G mRNA

You can find the mRNA sequence using the steps below Writing mRNA Sequences

Before leaving nucleus, mRNA must be processed Introns removed Exons spliced together Cap and tail added mRNA leaves nucleus Processing and Exit A U G U C C G U G A C G U G A C A A U G U G A A U G G A C G U G A C G U G A (cap) A U G G A C G U G A C G U G A (tail)

Proteins Complex macromolecule Polymer, made of amino acid chains – 20 different amino acids Order of amino acid specified in mRNA Codons – three consecutive nucleotides in mRNA Each codon specifics an amino acid Decoding the Genetic Code A U G G A C G U G A C G U G A

Each codon specifies one of 20 amino acids Decoding the Genetic Code A U G G A C G U G A C G U G A First nucleotide Second nucleotide Third nucleotide

Translation – process by which information in mRNA strand is used to create amino acid chain (polypeptide chain) Ribosome – protein complex where translation occurs tRNA – transfer RNA, bring amino acids to the ribosome Each has a specific anticodon and amino acid Translation

mRNA strand amino acid anticodon polypeptide chain tRNA codon Ribosome peptide bond

What polypeptide chain will be produced during translation if the mRNA strand below is used? Writing mRNA Sequences A U G U C A U C C G U G A C G U G A mRNA First nucleotide Second nucleotide Third nucleotide MetSer Val Thr stop

You can translate the mRNA sequence using the steps below Translating mRNA Sequences

Transcription “Copying” DNA to mRNA Occurs in nucleus RNA involved – mRNA Translation “Decoding” mRNA to polypeptide Occurs in cytoplasm RNA involved – mRNA – tRNA – rRNA Transcription and Translation

How does a polypeptide chain become a protein? Edited – Sections cut out by enzymes Folds – Amino acids bond together Editing & Folding

How does a molecule create a protein? 1.Transcription – mRNA strand made from DNA template 2.mRNA modified and leaves nucleus – Introns removed, cap and tail added 3.Translation – Polypeptide chain made at ribosome using mRNA 4.Polypeptide chain into protein – Edited & folded From DNA to Protein

Learning Objectives Describe how DNA is used to make protein Explain process of transcription – DNA to mRNA Explain process of translation – mRNA to polypeptide chain Transcription and Translation