Transcription: Copies the Information of DNA RNA: transcription = making complementary copy of _____ segment (is it an exact copy? Explain why or why not) made inside nucleus leaves nucleus and goes to ribosome in cytoplasm to direct synthesis of protein RNA differs from DNA -one strand -ribose sugar -uracil replaces ________ as fourth nitrogen base -is smaller than DNA three types of RNA: a. mRNA - carries "recipe" for protein to ____________ b. tRNA - carries ______ _______ to ribosomes c. rRNA - in ribosomes mRNA transcribed in nucleus: mRNA leaves nucleus and moves to ribosome to direct protein synthesis Codons Determine Amino Acid Sequence codon = group of three nitrogen b_________ on ______ that codes for an amino acid -also called triplets There can be 2 to 3 different codons for each a.a. (20-22) 1 codon (________) is start codon several stop codons Protein Synthesis Translation: Proteins are Synthesized mRNA moves to c________ and attaches to a r______ mRNA acts as template for protein synthesis tRNA has antic_______ that will match mRNA codons as ribosomes move across mRNA, tRNA brings appropriate a______ a_____ to it a________ acids bond together forming a peptide chain, which forms a polyp______, which, when reaching macromolecular size, it is a p__________ (polypeptide) Practice Questions: 1. Which is a five carbon sugar found in an RNA molecule? a. uracil b. ribose c. adenine 2. Which base is found in DNA but not in RNA? a. adenine b. cytosine d. glucose c. thymine d. uracil 3. The sequence of nucleotides in a messenger RNA molecule is determined by the sequence of nucleotides in a. transfer RNA molecule c. polysaccharide molecule b. protein molecule d. DNA molecule 4. In protein synthesis, the code for a particular amino acid is determined by a. the one gene-many enzyme hypothesis c. multiple alleles b. a sequence of three nucleotides d. the number of messenger RNA molecules 5. If the code for glutamic acid is ATG on the DNA molecule, this code on the transfer RNA molecule may be written as a. ATG b. CTG c. AUG d. GTA 6. To which organelles is messenger RNA attached? a. chloroplast b. ribosomes 3. mitochondria 4. vacuoles 7. During protein synthesis, amino acids are picked up in the cytoplasm and positioned at the ribosomes by a. unattached nucleotide molecules c. molecules of DNA b. polypeptide molecules d. molecules of RNA 8. In protein synthesis, which sequence of bases in transfer RNA will pair up with the sequence GGU found in the messenger RNA? a. CCT b. CCA c. AAC d. UUA 9. Which is the correct sequence of code transfer involved in the formation of a polypeptide? a. DNA, tRNA, mRNA c. mRNA, tRNA, DNA b. tRNA, DNA, mRNA d. DNA, mRNA, tRNA 10. The position of an amino acid in protein molecule is determined by the a. concentration of amino acids in the cytoplasm b. amount of ATP in the cell synthesizing the protein c. sequence of nitrogenous bases in DNA d. sequence of amino groups in the amino acid 11. A sequence of three nitrogenous bases in an mRNA molecule is known as a. codon b. gene c. polypeptide d. nucleotide 12. In the synthesis of proteins, what is the function of mRNA molecules? a. They act as a template for the synthesis of DNA. b. They carry information that determines the sequence of amino acids c. They remove amino acids from the nucleus. d. They carry specific enzymes for dehydration synthesis. 13. A change in the base sequence of DNA is known as a. a gene mutation b. a karyotype c. Nondisjunction d. polyploidy 14. Which nuclear process is represented below? a. recombination b. fertilization c. replication d. mutation Protein Synthesis Protein synthesis is a complex process. You will trace the steps that are involved in the protein synthesis of a part of a molecule of oxytocin. Oxytocin is the pituitary hormone that helps regulate blood pressure, stimulates the uterus to contract during childbirth, and stimulates the production of milk after childbirth. A. Protein synthesis begins with DNA in the nucleus. Below is a DNA sequence that could code for part of a molecule of oxytocin. ● Write the sequence of messenger RNA (mRNA) codons that would result from the transcription of this portion of DNA . The arrow marks the starting point (Nucleus) DNA TRANSCRIPTION: mRNA: (Codon) ACA - ATA - TAG - CTT - TTG - ACG - GGG - AAC - CCC - ATT 1 2 3 4 5 6 7 8 9 10 1 UGU 2 – UAU - 3 4 - 5 – 6 - 7 – 8 - 9 - 10 - B. After transcription (in nucleus), mRNA attaches to a ribosome where translation (in cytoplasm) takes place. Each codon of mRNA bonds with an anticodon of a transfer RNA (tRNA) and each tRNA molecule bonds with a specific amino acid. The table below shows the mRNA codons and the amino acids for which they code. For example, if you were given the codon AGA, you can see from the table that these bases code for the amino acid arginine. DNA triplet AAA GTC mRNA codon UUU UGA tRNA codon AAA Amino Acid Phenylalanine STOP Methionine (START) Use the information on the codon chart to fill in the following table. The first row has been completed to get you started. mRNA 1. UGU 2. UAU 3. 4. 5. 6. 7. 8 9. 10. Use the mRNA sequence from A to write the sequence (1 –10) of amino acids in this part of the oxytocin molecule. Cysteine - Tyrosine – – – – – – - STOP 1. How many amino acids make up this portion of the oxytocin molecule? _____ + 1 stop codon 2. What is the purpose of the UAA codon? C. In order to get another view of the entire process of protein synthesis, label the structures on the diagram below. (ribosome (rRNA), mRNA [codon=3 bases], tRNA [anticodon=3 bases], protein, DNA To complete the chart below, give the name and a brief description of each step in protein synthesis that occurs in the part of the cell shown in the diagram above. PART OF CELL Name of Protein Synthesis Process DNA __________ Nucleus ribosome cytoplasm Description RNA code _____ ______ protein modified polypeptide chains folded to into p_______ Base your answers to questions 1 through 3 on the diagram below showing a joining of two amino acids that occurs within cells. 1. The process represented in the diagram occurs on the cell organelle known as a a. vacuole b. ribosome c. chloroplast d. mitochondrion 2. Which amino acid would be transferred to the position of codon CAC? a. leucine b. glycine c. valine d. histidine 3. The process represented in the diagram is a. lipid digestion b. cell respiration d. protein hydrolysis c. protein synthesis Use the following choices for questions 4 through 7. Types of Nucleic Acid Molecules (1) DNA molecule, only (2) RNA molecules, only (3) Both DNA and RNA molecules (4) Neither DNA nor RNA molecules 4. May contain adenine, cytosine, guanine, and thymine. 5. Carry genetic information from nucleus to ribosomes. 6. Are present in the nucleus of the cell. 7. Consist of chains of nucleotides. 8. What is the process called which uses the information coded in DNA to chemically link amino acids into a chain? 9. The amino acid sequences of three species shown below were determined in an investigation of evolutionary relationships. Species A: Val His Leu Ser Pro Val Glu Species B: Val His Leu Cys Pro Val Glu Species C: Val His Thr Ser Pro Glu Glu Based on these data, which two species are most closely related? Support your answer.
