Read the lab handout COMPLETELY Read the lab handout COMPLETELY. Then answer the following pre-lab questions on p.17 of your journal. Introduction How is transcription different from DNA replication? What are the three specific ways RNA differs from DNA? What is transcription and where does it occur? What is translation and where does it occur? DO NOW Procedures Which template strand is copied and transcribed in the nucleus? How should you indicate the different codons on your lab sheet? How will you form a protein sentence? How are you going to decode the mRNA to find the appropriate amino acids?

Protein Synthesis Lab Essential Question: How is protein synthesis related to mutations?

Lab Instructions In this lab, you and your team will work together to TRANSCRIBE a strand of DNA into RNA and TRANSLATE a strand of mRNA into a chain of amino acids (protein). There will be THREE ROUNDS. In each round you will have a DIFFERENT JOB! Jobs mRNA: Goes to the nucleus and transcribes the DNA into mRNA and brings it back to the ribosome. rRNA: Stays in the ribosome and organizes the mRNA into codons while reading them to the tRNA. tRNA: Retrieves amino acids from the cytoplasm one at a time to form a protein sentence.

Lab Instructions - More Specifics mRNA starts in the nucleus (labeled table in the middle of the room) and randomly selects a DNA segment. mRNA copies the gene # and records it on their lab sheet. Then, mRNA “unzips” the DNA and copies the bold template strand on their lab sheet. Next, mRNA transcribes (pairs C – G, G – C, A – U, and T – A) the bold DNA strand into mRNA on their lab sheet. Once complete the mRNA goes to the ribosome.

Lab Instructions - More Specifics In the ribosome, the rRNA and the tRNA check the mRNA’s work to make sure the DNA template was transcribed correctly. Then, rRNA and tRNA copy down the information on their lab sheets. Next, the rRNA organizes the nucleotides in the mRNA strand into codons (draw lines) and tRNA and mRNA do the same.

Lab Instructions - More Specifics Now, rRNA reads out each codon to tRNA and tRNA goes to the cytoplasm to retrieve it and bring it back to the ribosome. rRNA and mRNA record the word on the back of the codon to form the protein sentence. THIS SENTENCE SHOULD MAKE SENSE

Lab Instructions - More Specifics Once complete, work as a group to use the codon chart to identify the real chain of amino acids. Repeat and change roles each time!

Mutations Mutations are changes in the DNA sequences. Changes to the order of nucleotides (A, T, C & G). Different order of nucleotides = different amino acid in protein. Different protein structure = different protein function.

What Causes Mutations? There are two ways in which DNA can become mutated: Mutations can be inherited. Parent to child. Mutation in the gametes (sperm or egg). Mutations can be acquired. Mutation in somatic cell. Mistakes when DNA is copied or damage to the DNA (mutagen).

Types of Mutations: Gene Mutations Typically occur during replication. May or may not show in phenotype Phenotype – the physical characteristics of an organism. Ex: Skin color, eye color, height Frameshift mutation: the insertion or deletion of a nucleotide in the DNA sequence. Point mutation: one nucleotide is substituted for another.

Gene Mutation

Types of Mutations 2. Chromosome Mutations Change to a group of genes or entire chromosome Typically happens during meiosis. Gene duplication: Crossing over goes wrong causing 1 chromosome to have 2 copies of a gene and the other chromosome to have none. Translocation: movement of a piece of one chromosome to a non- homologous chromosome.

Potential Impact to Phenotype Some mutations are harmful Reduce chances of survival. Some mutations are beneficial Increase genetic variation and chance of survival. Most mutations are neutral (Silent) Do not show any advantages or disadvantages. No effect on phenotype. Gene mutations can be silent NOT chromosomal mutations.

Potential Impact to Offspring What is the impact of a mutation in a somatic cell? Only impacts the organism in which they occur. Are not passed to offspring. What is the impact of a mutation in a gamete? Mutation can be passed to offspring. Source of genetic variation.

How are mutations relate to protein synthesis?

Bring it all together: Protein Synthesis Protein synthesis involves transcription and translation Step 1: Transcription (DNA to RNA) In the nucleus. Nucleotides: A, U, C, G. Step 2: Translation (RNA to protein) On the ribosomes. How many nucleotides code for an amino acid? 3= codon.

A codon chart is shown to the right. Which of these changes to the DNA triplet 3’ GCT 5’ will affect the protein produced? GTT TCC TCT GCA

The table shows a DNA sequence and three types of mutations that can change the DNA sequence. Which mutation will cause translation to stop? Mutations 1 and 3 only Mutation 1 only Mutation 2 only Mutations 1, 2, and 3

Which of the following carries amino acids to the site of protein synthesis? mRNA rRNA tRNA nRNA

The sequence of DNA below is part of a gene The sequence of DNA below is part of a gene. How many amino acids are coded for by this segment? 5' ATCAGCGCTGGC 3' 4 8 12 24