Transcript RNA
Structure and Function of RNA RNA- ribonucleic acid 1. RNA is a single strand 2. RNA is made up of smaller subunits called nucleotides 3. Nucleotides consist of: A. Sugar-ribose B. phosphate group C. nitrogen base-4 types 1. Adenine-A 2. Uracil- U 3. Guanine- G 4. Cytosine- C 4. Adenine(A) pairs with Uracil(U) and Cytosine(C) pairs with Guanine(G) 5. 3 kinds of RNA A. messenger(m) RNA- carries nucleotide sequence from nucleus to ribosome B. transfer(t) RNA-picks up amino acids in cytoplasm and carries them to ribosome C. ribosomal(r) RNA- found in ribosome, joins mRNA and tRNA Process of transcription 1. Transcription- process that makes RNA (messenger RNA) from DNA 2. DNA unzips into 2 separate strands 3. Free floating RNA nucleotides in the nucleus pair up with these unzipped DNA nucleotides A. Cytosine(C) pairs with Guanine(G) B. Uracil(U) pairs with Adenine(A) 4. After all the pairing is done, a single strand of RNA has been produced. 5. Genetic code from DNA is transferred to mRNA 6. The code obtained from DNA lets the mRNA know which amino acids to pick up A. code is a set of 3 nitrogen bases B. called a codon Section 12-3 Figure 12–14 Transcription Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNA polymerase DNA RNA Go to Section: Process of Translation 1. Translation- conversion of mRNA into amino acid sequence that makes up a protein 2. Occurs at the ribosomes 3. The mRNA leaves the nucleus and enters the cytoplasm 4. Ribosomes attach to mRNA 5. The mRNA is read by ribosomes 3 nucleotides(codon- A G C) at a time 6. As the codons are read, tRNA brings the appropriate amino acids together and they are assembled in a long chain called a protein 7. The genetic code ultimately tells the cell what proteins are made Translation Section 12-3 Figure 12–18 Translation Nucleus Messenger RNA Messenger RNA is transcribed in the nucleus. Phenylalanine tRNA The mRNA then enters the cytoplasm and attaches to a ribosome. Translation begins at AUG, the start codon. Each transfer RNA has an anticodon whose bases are complementary to a codon on the mRNA strand. The ribosome positions the start codon to attract its anticodon, which is part of the tRNA that binds methionine. The ribosome also binds the next codon and its anticodon. Ribosome Go to Section: mRNA Transfer RNA Methionine mRNA Lysine Start codon Figure 12–18 Translation (continued) Section 12-3 The Polypeptide “Assembly Line” The ribosome joins the two amino acids— methionine and phenylalanine—and breaks the bond between methionine and its tRNA. The tRNA floats away, allowing the ribosome to bind to another tRNA. The ribosome moves along the mRNA, binding new tRNA molecules and amino acids. Lysine Growing polypeptide chain Ribosome tRNA tRNA mRNA Completing the Polypeptide mRNA Ribosome Go to Section: Translation direction The process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain. Quiz #4 RNA 1. RNA is single stranded, made up of ___________. a. Proteins b. nucleotides c. thymines d. codons 2. Which nitrogen base for RNA does not belong? a. Uracil b. adenine c. cytosine d. thymine 3. mRNA is made from DNA through a process called _______. a. Replication b. translation c. transcription 4. Proteins are made from mRNA through a process called ____. a. Replication b. translation c. transcription 5. If a sample of DNA is A-C-T-T-G-A, what would the strand of RNA produced be? A. T-G-G-T-A-A B. U-G-A-A-C-U C. T-G-A-A-C-T