What was so important about DNA anyway?

1. What was so important about DNA anyway?

2. Protein Synthesis : the creation of Protein within a cell Section Objectives • Relate the concept of the gene to the sequence of nucleotides in DNA. • Sequence the steps involved in protein synthesis.

3. Genes and Proteins • The sequence of nucleotidesin DNA contain information. • This information is put to work through the production of proteins. • Proteins fold into complex, three-dimensional shapes to become key cell structures and regulators of cell functions. • Thus, by encoding the instructions for making proteins, DNAcontrols cells.

4. Genes and Proteins • You learned earlier that proteins are long chains of amino acids. • The sequence of nucleotides in each gene contains information for assembling the string of amino acids (building blocks of proteins) that make up a single protein molecule.

5. RNA (ribonucleic acid) • RNA has a different function than DNA • Whereas DNA provides the instructions for protein synthesis, RNA does the actual work of protein synthesis. • They take from DNA the instructions on how the protein should be assembled, then—amino acid by amino acid—they assemble the protein.

6. RNA (ribonucleic acid) Nitrogenous base(A, G, C, or U) Phosphategroup • RNA like DNA, is a nucleic acid • RNA structure differs from DNA structure in three ways. • 1. Has ribose sugar instead of deoxyribose (DNA) • 2. Replaces thymine (T) with uracil (U) • 3. Single stranded as opposed to double stranded DNA Uracil (U) Sugar(ribose)

7. RNA (ribonucleic acid) 3 types of RNA • 1. Messenger RNA (mRNA), single, uncoiled strand which brings instructions from DNA in the nucleus to the site of protein synthesis. • 2. Ribosomal RNA (rRNA), globular form, makes up the ribosome –the construction site of proteins binds (site of protein synthesis); binds to the mRNA and uses the instructions to assemble the amino acids in the correct order. • 3. Transfer RNA (tRNA) single, folded strand that delivers the proper amino acid to the site at the right time

8. DNA compared to RNA RNA • Single stranded • Contains base Uracil • Unable to self replicate DNA • Double stranded • Contains base Thymine • Able to self replicate

9. Protein Synthesis is a 2 step process:Transcription & Translation

10. Transcription • occurs in the nucleus, enzymes make an RNA copy of a portion of a DNA. • The main difference between transcription and DNA replication is that transcription creates a single stranded RNA moleculerather than a double-stranded DNA molecule.

11. Transcription Messenger RNA or mRNA is similar to DNA, except that it is a single strand, and it has no thymine. Instead of thymine, mRNA contains the base Uracil. In addition to that difference, mRNA has the sugar ribose instead of deoxyribose.

12. RNA Processing • Not all the nucleotides in the DNA of eukaryotic cells carry instructions—orcode—for making proteins. • Genes usually contain many long noncoding nucleotide sequences, called introns, that are scattered among the coding sequences. • Regions that contain information are called exons because they are expressed. • The mRNA then leaves the nucleus and travels to the ribosome.

13. RNA Processing • Noncoding segments are called introns are spliced out.

14. Worksheet 1 - Transcription For each of the strands, report the RNA transcript. 1. AGTCCTGAGAACT - DNA - RNA 2. AAAGTGTCTGTTTT - DNA - RNA 3. CCGCGCTTCTCGAG - DNA - RNA Answer the following questions by filling in the blanks 4. DNA Transcription takes place in the ____________________. 5. _______, _______, and _______ are the three types of RNA. 6. Guanine on DNA will link with ______________ in RNA. 7. ______________ on DNA will link with adenine in RNA. 8. Adenine on DNA will link with ______________ in RNA.

15. Genetic information written in codons is translated into amino acid sequences • Transfer of DNA to mRNA uses “language” of nucleotides • Letters: nitrogen bases of nucleotides (A,T,G,C) • Words: codons ~triplets of bases ( ex. AGC) • Sentences: polypeptide chain (a single strand of amino acids). • The codons in a gene specify the amino acid sequence of a polypeptide chain.

16. Translation -from mRNA to Protein • process of converting the information in a sequence of nitrogenous bases in mRNA into a sequence of amino acids in protein is known as translation. • takes place at the ribosomes in the cytoplasm. Involves 3 types of RNA 1. Messenger RNA (mRNA) =carries the blueprint for construction of a protein 2. Ribosomal RNA (rRNA) = the construction site where the protein is made 3. Transfer RNA (tRNA) = the truck delivering the proper amino acid to the site at the right time

17. The Genetic Code • The nucleotide sequence transcribed from DNA to a strand of messenger RNA acts as a genetic message, the complete information for the building of a protein.. • Virtually all organisms share the same genetic code

18. Transfer RNAmolecules serve as interpreters during translation • In the cytoplasm, a ribosome attaches to the mRNA and translates its message into a protein. • The process is aided by transfer RNAs (tRNA). • Each tRNA molecule has a triplet anticodon on one end and an amino acid attachment site on the other • An anticodon base pairs with a codon of mRNA

19. mRNA codon and tRNA anti-codon

20. Worksheet 2 - Translation 1. If the DNA sequence is --- AAA TAT CCG TAG, write the mRNA sequence, tRNA anticodon sequence, and the four amino acids for this protein. DNA: TAG AAA TAT CCG mRNA: _____ _____ ____ _____ tRNA: _____ _____ ____ _____ Amino acids: _____ _____ ____ _____

21. Worksheet 2 – Translation Chart

22. In Summary Ribosome

23. GFP Green Fluorescent Protein is a protein composed of 238 amino acids Martin Chalfie, Osamu Shimomura, and Roger Y. Tsien were awarded the 2008 Nobel Prize in Chemistry on October 10, 2008 for their discovery and development of the green fluorescent protein.