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Lecture 37

Lecture 37. Mr. Sover 17 November 2009. Collect Homework. Quiz. Clear off your desks. No talking. Quiz. 1. If the DNA sequence is AGC TTA, what will be the RNA sequence? 2. Instead of Thymine, which nitrogen base is used in RNA? 3. Instead of deoxyribose, which sugar is used in RNA?

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Lecture 37

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  1. Lecture 37 Mr. Sover 17 November 2009

  2. Collect Homework

  3. Quiz • Clear off your desks. • No talking.

  4. Quiz • 1. If the DNA sequence is AGC TTA, what will be the RNA sequence? • 2. Instead of Thymine, which nitrogen base is used in RNA? • 3. Instead of deoxyribose, which sugar is used in RNA? • 4. Is RNA a single or double helix? • 5. If you could be any animal, which would you be and why?

  5. Begin Lecture • Take out your notes!

  6. The DNA Code • What is a gene? • A gene is a segment of a DNA molecule that carries the code for the synthesis of a particular polypeptide. • A polypeptide is made up of many amino acids. • Order of the amino acids is important. • Genes direct this order.

  7. 20 Amino Acids • 20 amino acids exist. • Each set of three bases representing an amino acid is known as a codon. • When considering three nitrogen bases together, 64 combinations arise. • The cell “reads” these codons and links together certain amino acids to form a particular polypeptide (to make a protein).

  8. Three of the codons act as a “stop signals” like periods at the end of sentences. • They show the end of the code for a particular polypeptide.

  9. The DNA code is universal.

  10. Polypeptide Synthesis • As we talked about yesterday, genes code for the synthesis of polypeptides. • (Genes code for polypeptides) • Each gene is a segment of a DNA molecule and consists of a chain of nucleotides. • DNA is located in the nucleus of the cell. • Proteins are synthesized OUTSIDE the cell at the what??

  11. How does the DNA get from the nucleus to the ribosome? • Another type of ribonucleic acid exists in the nucleus as well as the CYTOPLASM.

  12. Structure of RNA • RNA’s structure is similar to that of DNA. • However Three Differences… • 1. • 2. • 3.

  13. Cells synthesize proteins as they are needed. • Near each gene is a section of DNA which is a start signal for the synthesis of each needed polypeptide. • The DNA unzips as an enzyme attaches to it (much like that in DNA replication). • RNA nucleotides join. • Double helix zips back up.

  14. The process of making RNA from DNA is called what?

  15. This RNA is not called just RNA… • It has a special name… • Some DNA codes for other things than polypeptides. • rRNA

  16. Transcription in Eukaryotes • DNA is wound around spools of protein called histones. • The DNA must be unwound from these spools.

  17. After mRNA is formed… • mRNA will break apart and reform together as a shorter strand.

  18. Homework • P. 270 1-4

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