From Gene to Protein

From Gene to Protein Goal 1- Understand How to Read the Genetic Code Steps in Cracking the Code Overview of Gene Expression How to get from a Gene to a Protein Goal 2- Demonstrate How to Read the Genetic Code Genetic Code - Model activity

Try This! • What is a gene? • If every cell in your body has the same DNA, how does a heart cell, or liver cell, or a brain cell, for example, know how to “act” like heart cells, liver cell, or brain cells?

The Big Picture • DNA replication provides the copies of genes that parents pass to offspring. • However, it is not enough that genes be copied and transmitted; they must also be expressed. • How do we get from genotype to phenotype? • Genotype: the genetic make-up of an organism (i.e., blueprint; total set of instructions for being human) • Phenotype: The physical and physiological traits of an organism (i.e., specific set of instructions for being you; eye colour, height, body type, fast runner, etc.)

An Analogy of Gene Expression Transcribe (copy) a set of ingredients from the cookbook to make a recipe Translate the ingredients into a dish

Imagine that you have a large, old, and valuable cookbook that's been in the family for generations. You want to cook a your grandmother’s delicious banana muffins. Obviously you don't want to get your book soiled with muffin batter, so when you want to make use of a recipe you might copy a page by hand onto a piece of paper to use at the stove-side. The process of transcription is like making a handwritten copy of a page from the original text for actual use. It's a working copy. • In this analogy, the cookbook is equivalent to the totality of DNA in an organism -- the genome. On this DNA are many regions called genes. They are the recipes for how to construct proteins. The handwritten copies of recipes are mRNA's. They are transcripts of the text (that is, a copies in the same language but in a different form) that are being used at a specific time and place for a specific purpose (to construct certain proteins). Note that it is possible to make many copies of a single recipe, and similarly, it is possible to transcribe many copies of a gene. It is possible, as well, to copy more than one recipe -- for example, for a vegetable side dish and desert as well as the main dish -- in preparing a meal.

Basics of Gene Expression “Cookbook” (genotype) nucleus “Copy of recipe” “Dish” (phenotype) cytoplasm

Molecular Basis of Gene Expression • Gene expression is how the cell translates particular or specific genetic information encoded in DNA • Translated genetic information is then used to make functional proteins that govern the characteristics of each cell type (controls how the cell will function) • Each cell type (i.e., heart cell, brain cell) expresses some genes from the total genome, but not others, which is what makes them unique from other cells.

Try This! • What is a protein? • How many amino acids are there?

From Gene to Protein Questions: • What is a gene? • What is messenger RNA (mRNA) and what is the process that makes it? • What is a codon? • How is mRNA used to make a protein and what is this process called?

The Genetic Code • The genetic code is a language that uses sequences of nucleotides as instructions for constructing a protein. • Recall that a proteins consists of specific sequences of amino acids arranged in a polypeptide chain. • The code is read in groups of three. • Nucleotide triplets (codons) specify a particular amino acid • Cell translates genes into proteins using the intermediate step of translation (complementary mRNA molecule to the DNA template strand)

Cracking the Genetic Code “ ” “ ” “ ” ” “ START

Homework: Cracking the Code • Complete the “Cracking the Code” activity to determine which protein you are. • Submit your cracked code on Wednesday.

Review: From Gene to Protein • Transcription and Translation are the two main processes linking gene to protein

From Gene to Protein