Introduction to Protein Synthesis “What is the connection between the proteins an organism synthesizes and the phenotype it has?”

What scientific evidence can we use to say, Do Now: Observe the picture of the siblings. Write four statements that suggest they are siblings. What scientific evidence can we use to say, “they are siblings?”

Genetic material of the cell explains the sibling similarities. The chromosomes are homologous because they are a matched pair. One came from the mom and the other from dad. (Siblings may share forms of genes)

Watch Simple Gene Expression Animation Must understand the structure of homologous chromosomes, the structure of the gene, and protein synthesis. Write an explanation using some of the terms shown to tell why the 3 red-headed siblings have similar phenotypes. Watch Simple Gene Expression Animation Click on next slide for more help

Overview: The Flow of Genetic Information The information content of DNA is in the form of specific sequences of nucleotides called the gene. The DNA inherited by an organism leads to specific traits by dictating the synthesis of proteins. Chromosomes are the distinct structures of DNA. A person inherits chromosomes from each parent. Hence, chromosomes are paired. Gene pairs are what determine the phenotype of an organism. Gene expression, the process by which DNA directs protein synthesis, includes two stages: transcription and translation. Remember, proteins come in many types so they can do different things. The ribosome is an organelle directing polypeptide synthesis.

Intro to Protein Synthesis: Points to Remember How was the fundamental relationship between genes and proteins discovered? Through experiments!!!!!!! Scientists learned that if the gene was mutated or removed from the chromosome, no protein could be made or some would not be made correctly. Central Dogma is written as: DNA (Gene)  mRNA  polypeptide

Intro to Protein Synthesis: Points to Remember Because all proteins aren’t enzymes, researchers revised the hypothesis: one gene–one protein Many proteins are composed of several polypeptides, each of which has its own gene. Therefore, the thought is now restated as one gene–one polypeptide. Many polypeptides make up protein which could be a transport, signal, receptor, contractile, etc.

In prokaryotes, mRNA produced by transcription is immediately translated without more processing In a eukaryotic cell, the nuclear envelope separates transcription from translation Eukaryotic RNA transcripts are modified through RNA processing to yield finished mRNA Cells are governed by a cellular chain of command: DNA RNA protein

The Genetic Code: Information for making proteins and determining sibling’s phenotype How are the instructions for assembling amino acids into proteins encoded into DNA? There are 20 amino acids, but there are only four nucleotide bases in DNA So how many bases correspond to an amino acid?

Look at Protein Synthesis- Oxytocin wkst During transcription, a DNA strand called the template strand provides a template for ordering the sequence of nucleotides in an RNA transcript (mRNA) During translation, the mRNA base triplets, called codons, are read in the 5 to 3 direction Each codon specifies the amino acid to be placed at the corresponding position along a polypeptide Look at Protein Synthesis- Oxytocin wkst

Amino acid codon chart LE 17-5 Second mRNA base First mRNA base (5¢ end) Third mRNA base (3¢ end)

Can you use the codon chart to prove the order of amino acids? LE 17-4 Gene 2 DNA molecule Gene 1 Gene 3 DNA strand (template) 3¢ 5¢ Can you use the codon chart to prove the order of amino acids? TRANSCRIPTION mRNA 5¢ 3¢ Codon TRANSLATION Protein Amino acid

DO Now #1 DNA: TAA GGT AAA TGC ACT - write the complementary RNA… RNA: AUU CCA UUU ACG UGA 1. How many codons are in RNA? 2. How many amino acids “could” be in the polypeptide chain? What does a codon represent? Amino acid, start of translation, stop translation

Why use the bottom strand of DNA to make mRNA? DO Now #2 DNA: 5’ ATGTGGAACCGTAGCTGA3’ DNA: ????? Write the complementary DNA to complete the DNA structure. Synthesize a strand of mRNA from the above piece of DNA. mRNA: 5’AUG UGG AAC CCU GCU GA 3’ mRNA synthesized in the 5’ to 3’ direction When reading mRNA, read from left to right (5’ to 3’) Why use the bottom strand of DNA to make mRNA? “The structure of ribose”