Gene Expression = Protein Synthesis

An organisms trait’s are determined by proteins that are built according to the plans specified in its DNA. (not in notes)

Gene Expression Over View

By altering the DNA, you are able to alter the proteins causing different results.

What are Genes? Hold information specifying how to build particular proteins. Referring back to the gym socks what part of the sock did the gene represent? Not in Notes-REVIEW

Genes are the DNA-encoded information that specifies particular proteins; each gene is made of a specific sequence of ____________??? nucleotides Not in Notes-REVIEW

Transcribe and Translate a Gene The DNA that makes up the human genome can be subdivided into information bytes called genes. Each gene encodes a unique protein that performs a specialized function in the cell. The human genome contains more than 25,000 genes.

Cells use the two-step process of transcription and translation to read each gene and produce the string of amino acids that makes up a protein. The basic rules for translating a gene into a protein are laid out in the Universal Genetic Code.

How do you build a protein? It goes through two steps. The first step is to undergo TRANSCRIPTION and make mRNA!!!

Transcription 1st step In the nucleolus the cells machinery copies the gene sequence into messenger RNA (mRNA), a molecule that is similar to DNA. Like DNA, mRNA has four-nucleotide bases-but in mRNA, the base uracil (U) replaces thymine (T).

Creating new strands DNA: GGTATCGATTGG 1st RNA: CCAUAGCUAACC 2nd RNA GGUAUCGAUUGG  

DNA vs. RNA DNA Double strand 5-C sugar deoxyribose Nitrogen bases: ATCG RNA Single strand 5-C sugar ribose Nitrogen bases: AUCG Uracil is complementary to adenine

                                                           

RNA polymerase Binds to a promoter Unwinds and breaks sequence Builds up sequence by pairing up each nucleotide with its complementary base (2 for 1 special)

What is the Role of DNA in this Process? DNA contains information about RNA.  RNA is built by using DNA as a template. The DNA is unzipped and mRNA is created as a complementary strand.   The new mRNA strand is not a copy of  the whole DNA strand, but only contains information about one gene. DNA’s job is to act as a template to make mRNA.

Step 1: RNA polymerase binds to gene’s promoter

Step 2: The two DNA strands unwind and separate

Step 3: Complementary RNA nucleotides are added

Step 4 Reaches terminator and stops

Step 5

Transcription                                                                                                                                                                   

Add INTRONS and EXONS to your vocab list to page 3 Introns: the noncoding sequences called intervening sequences Exons: the nucleotide segments that code for amino acids.

INTRONS and EXONS Transcription copies the DNA code of a gene and converts it to messenger RNA (m RNA). The m RNA will be used at the ribosome to make polypeptides (proteins). However all of the code contained in the m RNA molecule is not needed to produce the polypeptide. The sections of m RNA which do not code for translation of polypeptide are called introns.

INTRONS and EXONS As the m RNA readies itself to leave the nucleus, enzymes cut out and remove the introns. The remaining exons are spliced back together again by a different enzyme. This modified m RNA is what comes to the ribosome to be translated into polypeptides.

RNA 3 TYPES: messenger RNA (mRNA) ribosomal RNA (rRNA) transfer RNA (tRNA) Transcription manufactures 3-types of RNA

mRNA 1st built – in nucleus, leaves nucleus Holds the information from DNA and passes it on to create a protein It’s an RNA copy of a gene used as a blueprint for a protein. When a cell needs a particular protein, a specific mRNA is made.

rRNA Associates with protein to form the ribosome

tRNA – 2nd built, built in the ribosome, code for amino acids Acts as an interpreter molecule, translating mRNA sequences into amino acid sequences

Genetic Code After transcription the genetic material message is ready to be translated from the language of RNA to the language of proteins. The instructions for building a protein are written as a series of 3 nucleotide sequences called codons.

Codons in mRNA

Translation: 2nd Step The protein-making machinery, called the ribosome, reads the mRNA sequence and translates it into the amino acid sequence of the protein. The ribosome starts at the sequence AUG, then reads 3 nucleotides at a time. Each 3-nucleotide codon specifies a particular amino acid. The “stop” codons (UAA, UAG, and UGA) tell the ribosome that the protein is complete.

Overview DNA duplicates itself in replication. DNA produces RNA in transcription. RNA produces proteins in translation.

Drawing TIME!!  Pull out a sheet of paper

Transcribe a DNA sequence into a protein

DNA, RNA, and Proteins                                                                                                                                            

Extra Slides

Transcription Transcription is the process of creating RNA from DNA. Transcription occurs in the cell's nucleus. RNA polymerase is the protein molecule that reads the DNA and creates the RNA intermediary. Transcription requires: DNA, RNA polymerase, ribonucleotides, and some ATP for energy. Uracil (U) is substituted for thymine (T) in RNA. Transcription initiation is the main point of regulation of gene expression.