DNA & Gene Expression Transcription & Translation Structure & Function of DNA DNA Replication Genetic Code & 3 Types of RNA Transcription & Translation

KERATIN GENE EXPRESSION Genetic information is stored in units called genes Genes are arranged end to end on a strand of DNA Each gene is converted into a protein (Gene Expression) KERATIN GENE 1 GENE 2 GENE 3

Transcription The first step of gene expression, in which a particular segment of DNA is copied into mRNA by the enzyme RNA polymerase.

Transcription – Making mRNA Messenger RNA (mRNA) molecules are made by the process called ______________ ***RNA is a single-stranded nucleic acid that temporarily carries genetic information Transcription Transcription occurs in the cytoplasm in prokaryotes, and in the nucleus in eukaryotes. In transcription, a gene is transcribed/copied onto mRNA in order to synthesize a protein.

Transcription 2. Where does transcription occur in each of the following types of cells? Prokaryotic cell: _________________ Eukaryotic cell: __________________ Cytoplasm Nucleus

Transcription 3. Only a small section of DNA called a ________ is transcribed to make a mRNA. Gene

Transcription 4. Only _______ strand of the DNA molecule called the ___________ strand is transcribed to make a mRNA. one template

5. Process of Transcription A. A small section of the _________ molecule called a gene unwinds. DNA B. The two strands of DNA separate. This exposes the __________________ of the DNA molecule. nitrogen base

5. Process of Transcription C. RNA nucleotides floating around in the nucleus pair with the complementary nitrogen bases in only 1 strand, the ____________strand of DNA. They pair up according to the base-pairing rules except that uracil replaces thymine in RNA. Therefore, _______ bonds with _______ and _______ bonds with _______. D. The RNA nucleotides are ___________ together. template A G U C linked

5. Process of Transcription The new mRNA molecule is released, leaves the nucleus, and travels to a ___________________________. The section of the DNA molecule that was transcribed __________ up. ribosome closes

Make the mRNA molecule for the DNA Template DNA Strand A T G C A G A T mRNA Strand T A C G T C T A Non-template DNA Strand

Review questions 1. Where in the eukaryotic cell does transcription occur? _________________________________ 2. What molecule is made by transcription? ___________________________________________ 3. How are the base-pairing rules for transcription different from the base-pairing rules for DNA replication? ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ 4. Show the mRNA strand that will be made by transcribing the section of DNA shown below. DNA template: A T C G C C T A C T A G mRNA strand: DNA  RNA 

DNA & Gene Expression Transcription & Translation Structure & Function of DNA DNA Replication Genetic Code & 3 Types of RNA Transcription & Translation

Translation – Making Proteins The second/final step of gene expression is translation. Messenger RNA (mRNA)—produced by transcription from DNA—is decoded by a ribosome to produce a specific amino acid chain, or polypeptide. The polypeptide later folds into an active protein and performs its functions in the cell.

Protein Synthesis translation 1. The final stage of gene expression is _____________. 2. ____________ is the process by which RNA is used to assemble amino acids into ____________. translation Translation proteins

Protein Synthesis 3. Translation occurs in the ___________ of the cell on a structure called the _________. cytoplasm ribosome

Building a polypeptide Chain 4. A ____________________ is a 3-nitrogen base segment of mRNA that signifies the beginning of the instructions for a chain of amino acids. start codon Start Codon = AUG (like the “start” of school) stop codon 5. A __________________ is a 3-nitrogen base segment of mRNA that signals the end of the instructions for a chain of amino acids. Ex: UGA

Process of Translation Once the messenger RNA (mRNA) leaves the nucleus, it moves through the cytoplasm until it binds to a small ribosomal subunit. A ribosome forms around the mRNA molecule; the mRNA passes through it. tRNA molecules carrying amino acids begin binding to the codons of the mRNA; the tRNA contains a complimentary anticodon. The amino acids form peptide bonds, creating a long polypeptide chain until the stop codon on the mRNA is reached. Once the complete polypeptide detaches from the ribosome, it folds to form a protein molecule.

Process of Translation A. A __________________ molecule binds to a small ribosomal subunit. B. A large ribosomal subunit attaches to the small ribosomal subunit to form a complete ______________________. The mRNA will pass through it. mRNA ribosome

Process of Translation tRNA tRNA C. A ________________________ molecule carrying an amino acid with the anticodon that is complementary to the start codon binds to the start codon on the mRNA. D. A tRNA molecule carrying an amino acid with the complementary ________________ binds to the second mRNA codon, and the first two amino acids are joined together. anticodon

Amino Acids “join together” by forming Peptide Bonds 1 2 4 3

Process of Translation E. The first tRNA molecule ______________ and moves away from the ribosome. Translation continues until a stop codon enters the ribosome. F. The completed amino acid chain is released. It begins to fold and may combine with other amino acids to form a ___________ molecule. detaches protein

Gene Expression 1 2 3 Watch the animation of Gene Expression at: https://www.youtube.com/watch?v=gG7uCskUOrA

GENE EXPRESSION Nucleus Ribosome 1 DNA 3 4 2 Protein transcription mRNA transcription 1 DNA 3 Protein Translation 4 2

Name the Parts of the Diagram:

mRNA: A U G C C U G A U C G G A A A U A G tRNA: -Complete the complementary tRNA anticodon that will match up with the mRNA codon. -Then, use the genetic code to name the amino acid mRNA: A U G C C U G A U C G G A A A U A G tRNA:

Practice identifying the amino acid coded for by each of the following mRNA codons. mRNA Amino Acid AUG UAC CAC ACG GUC UAG

Stages of Protein Synthesis: