How Proteins are Made

How RNA differs from DNA 1st- RNA consists of a single strand of nucleotides instead of the 2 strands found in DNA RNA DNA

How RNA differs from DNA 2nd- RNA nucleotides contain the five-carbon sugar ribose rather than the sugar deoxyribose found in DNA One less Oxygen

How RNA differs from DNA 3rd- RNA has A, C, G, and U- Uracil (U bonds with A because no T in RNA) Example: DNA ATGCATCG RNA UACGUAGC

RNA Nucleotide: Adenine, Guanine DNA Nucleotide: Adenine, Guanine RNA Nucleotide: Uracil, cytosine DNA Nucleotide: Thymine, cytosine

Transcription and Translation The instruction for making a protein are transferred from a gene to an RNA molecule in a process called transcription.

Transcription and Translation Cells then use 2 different types of RNA to read the instructions on the RNA molecule and put together the amino acids that make up the protein in a process called translation.

Transcription: Making RNA Step 1: Transcription begins when RNA polymerases bind to the gene’s promoter (a specific sequence of DNA that acts as a “start” signal for transcription.

Transcription: Making RNA Step 2: RNA polymerases then unwind and separate the 2 strands of the double helix, exposing the DNA nucleotides on each strand.

Transcription: Making RNA Step 3: RNA polymerase adds and then links complementary RNA nucleotides as it “reads” the gene.

Transcription Messenger RNA (mRNA) is a form of RNA that carries the instructions for making a protein from a gene and delivers it to the site of translation. http://10.11.3.62/videos/The%20Language%20of%20Life%20Understanding%20the%20Genetic%20Code/sec7268_300k.asf

Gene Regulation and Structure In eukaryotes, many genes are interrupted by introns (long segments of nucleotides that have no coding information.

Gene Regulation and Structure Exons are the portions of a gene that are translated (expressed) into proteins.

Gene Regulation and Structure The exons that remain are “stitched” back together by the spliceosomes to form a smaller mRNA molecule that is then translated.

Transcription & Codons The RNA instructions are written as a series of three-nucleotide sequences on the mRNA called codons. mRNA: AUGGGGCACAAAUAA Codons: _____ 5

mRNA Codon Chart

****EOC QUESTIONS**** A short chain of DNA has the nucleotide sequence ATA CCG. Its complementary mRNA nucleotide sequence is B. UAU GCC A. TAT GCC C. TUT GCC D. UAU GGC

****EOC QUESTIONS**** What is the maximum number of amino acids that could be coded for by a section of mRNA with the sequence GUCCAGAACUGU? A. 3 B. 4 C. 6 D. 12

****EOC QUESTIONS**** What is the name of the amino acid coded by AGU? ___________________ Serine

Translation: Assembling Proteins Transfer RNA (tRNA) molecules are single strands of RNA that temporarily carry a specific amino acid on one end.

Translation: Assembling Proteins An anticodon is a three-nucleotide sequence on a tRNA that is complementary to an mRNA codon.

****EOC QUESTIONS**** If a codon reads UGU, what is its anticodon? A. TCT B. AGA D. ACA C. UGU

Translation: Assembling Proteins Ribosomal RNA (rRNA) molecules are RNA molecules that are part of the structure of ribosomes.

Steps of Translation Step 1: The ribosomal subunits, the mRNA, and the tRNA carrying methionine bind together. Step 2: The tRNA carrying the amino acid specified by the codon in the A site arrives.

Steps of Translation Step 3: A peptide bond forms between adjacent amino acids. Step 4: The tRNA in the P site detaches and leaves its amino acid behind.

Steps of Translation Step 5: The tRNA in the A site moves to the P site, the tRNA carrying the amino acid specified by the codon in the A site arrives. Step 6: A peptide bond is formed. The tRNA in the P site detaches and leaves its amino acid behind.

Steps of Translation Step 7: The process is repeated until a stop codon is reached. The ribosomes complex falls apart. The newly made protein is released. http://10.11.3.62/videos/The%20Language%20of%20Life%20Understanding%20the%20Genetic%20Code/sec7269_300k.asf

EOC Test Prep 1. Which cellular function does this model represent? A. Transcription B. Translation C. Transformation D. DNA replication

EOC Test Prep 2. Which part of the model represents a codon? F. A G. B *** Codons are associated with mRNA H. C J. D

EOC Test Prep 3.What does the part labeled E represent? A. Ribosome The circles represent amino acids which are what proteins are made up of. B. Growing protein chain C. Messenger RNA D. Transfer RNA

Practice mRNA- U G G A C A U U G C U C G G U C A A tRNA- A C C DNA- A C C T G T A A C G A G C C A G T T mRNA- U G G tRNA- A C C Codon - _____ Amino Acid- Trp A C A U U G C U C G G U C A A U G U A A C G A G C C A G U U 6 Thr Leu Leu Gly Gln