2. DNA vs. RNA

3. DNA DNA – Deoxyribonucleic Acid – Found in a cell’s nucleus – Function: to carry genetic information – Monomer: nucleotide 5 carbon sugar: deoxyribose Phosphate group Nitrogenous base

4. DNA, cont’d Nitrogenous Bases Adenine, Guanine, Cytosine, Thymine Purines: 2 rings in their structure Adenine, Guanine Pyrimidines: 1 ring in their structure Cytosine and Thymine

5. DNA, cont’d Double Helix Shape Sugar Phosphate Backbone: “sides” of the ladder Nitrogenous Base Pairs: “steps” of the ladder Adenine pairs with Thymine Guanine pairs with Cytosine Held together with hydrogen bonds

6. RNA RNA – Ribonucleic acid – Found in a cell’s cytoplasm and nucleus – Function: helps to make proteins using DNA’s genetic code – Monomer: nucleotide 5 carbon sugar: ribose Phosphate group Nitrogenous base – Nitrogenous Bases Adenine, Guanine, Cytosine, Uracil – Shape Single Stranded – There are three kinds of RNA mRNA, rRNA, tRNA

7. mRNA (Messenger RNA) – Carries set of instructions for assembling amino acids from the DNA to the rest of cell – long single strand of nucleotides – Copies DNA into complementary codons A codon is a sequence of 3 nucleotides that are read as a “word” A codon directs a specific amino acid to be used to build a protein

8. ribosomal RNA: takes up the major part of ribosomes; involved in protein synthesis transfer RNA: transfers each amino acid to the ribosome

9. tRNA (Transfer RNA) – Responsible for converting information found in mRNA into a sequence of amino acids, which build a protein – Contains an anticodon A sequence of bases complementary to a particular codon – Transfers each amino acid to the ribosome in a process called translation

10. Comparing DNA and RNA

11. Compare/Contrast RNA and DNA 1. 2. 3. 4. 1. 2. 3. 4. 5. 1. 2. 3. 4. 5. 6. DNA RNA

12. Compare/Contrast RNA and DNA 1. Deoxyribose sugar 2. Double ladder 3. Thymine 4. Replication 1. Ribose sugar 2. Half Ladder 3. Uracil 4. Can leave the nucleus 5. Translation 1. Cytosine 2. Guanine 3. Adenine 4. Phosphate 5. Nucleus of cell 6. Transcription DNA RNA

13. PROTEIN SYNTHESIS (making proteins) – Transcription – the process whereby DNA is copied into mRNA into series of codons Steps: 1.RNA polymerase (notice the ase!) binds to DNA and separates the strands 2.RNA polymerase uses the coding strand to then assemble a single strand of mRNA » Coding Strand: the side of the DNA strand that is used as a template to make the complementary strand of mRNA » Non-Coding Strand: the side of the DNA strand that is not used to make mRNA Translation Movie

14. 1. Transcription Transcription is the process whereby a sequence of DNA is copied into a complementary sequence of RNA.

15. THINK ABOUT IT Definition of TRANSCRIBE (from Miriam Webster Dictionary) a : to make a written copy of b : to make a copy of (dictated or recorded matter) in longhand or on a machine (as a typewriter) c : to paraphrase or summarize in writing d : write down, recordwrite downrecord If you borrow someone’s notes you TRANSCRIBE (copy them). You want to make an exact copy, to get all the info, but you may make minor changes to help you understand it better. TRANSCRIPTION: When copying the DNA a minor change is made THYMINE  URACIL (something the RNA understands better)

16. RNA polymerase starts making the copy of RNA at specific sites in the DNA known as promoters. There are similar places in the DNA that also tell the RNA polymerase to stop. RNA polymerase uses one of the strands to copy the genetic information into a strand of RNA. During transcription, DNA is unwound and separated by an enzyme called RNA polymerase.

17. Some parts of the original DNA strand contained sequences of nucleotides called introns that are not involved in coding for proteins. These must be taken out of the newly made RNA strand. The remaining nucleotides that are involved in coding for proteins are called exons. Now it is ready to go as a mRNA molecule!

18. DNA is “read” by RNA and copied into a complementary strand. That strand tells the cell which amino acids to make. mRNA n A string of amino acids is known as a protein. Different orders of amino acids make different proteins.

19. THINK ABOUT IT Definition of TRANSLATE (from Miriam Webster Dictionary) a : to turn into one's own or another language In your foreign language courses you go back and forth between languages. One does not understand the other, but they have the same meaning. TRANSLATION: the language is changing from that of NITROGEN BASES into that of AMINO ACIDS.

20. 2. Translation 1. RNA is transcribed from DNA and released into the cytoplasm 2. mRNA attaches to a ribosome. 3. Each codon is “read” and an amino acid is brought INTO the ribosome by tRNA. a. The first amino acid to be read is called the “start” codon because it starts the process of translation. i. AUG: methionine b. Each amino acid has its own specific tRNA “carrier.” c. One end of each tRNA has a specific amino acid and the other end has three unpaired bases. These bases are called the anticodon, and are complementary to three bases on mRNA.

21. Translation Steps Cont. 4. The amino acid is strung together to make a protein inside the ribosome by forming a peptide bond between each amino acid and by being removed from the tRNA molecule. 5. This process continues until the ribosome reaches a stop codon on the mRNA molecule. This signals the process of translation to stop and a complete protein is now formed. a. There are three stop codons: UAA, UAG, and UGA

22. DONE!! Now, a protein (chain of amino acids) has been made by using transcription and translation.

23. Transcription Animation! http://www.biostudio.com/demo_freeman_ protein_synthesis.htm

24. mRNA's instructions are called the GENETIC CODE. The genetic code is read three letters at a time, so each “word” is three bases long. Remember that the bases of RNA are A, U, C, and G; the “word” is written from these four letters. The mRNA “word” that is three bases long is called a codon. A codon is three consecutive nucleotides long and specifies a single amino acid.

25. Review…Importance Replication – DNA copies itself before cell division so EACH cell has identical instructions (blueprint) Transcription – Makes the mRNA codons from DNA which describe the specific order of amino acids needed to build a protein Translation – “reads” the mRNA codons and releases amino acids in the correct order to make a protein

26. Questions to Think About… Answer these with either transcription or translation… 1.Which one should happen in the nucleus (if a eukaryote)? (think about this!) 2.Which one makes mRNA? 3.Which one directly makes protein? 4.Which one occurs first? 5.Which one requires RNA polymerase?

27. 12-5 PAP Gene Regulation Only a fraction of genes are expressed in a cell at any given time. Determining whether a gene will be expressed or “silent” depends on several different structures. These different structures are often regulatory sites that are next to the promoter.

28. Prokaryote Gene Regulation Prokaryotes are arranged in groups of genes that are turned off and on together. Operon – group of genes that operate together These genes are turned off by repressors and turned on when RNA polymerase binds to the promoter.

29. On the DNA sequence there is a region where repressors can bind and turn off the gene. Operator – region of the chromosome in an operon to which the repressor binds when the operon is turned off When the repressor is bound the gene is turned off because it blocks RNA polymerase from binding inhibiting transcription

30. Eukaryotic Gene Regulation: Most eukaryotic genes are controlled individually and have regulatory sequences that are more complex than prokaryotic. In eukaryotes, there is a short region of DNA about 30 base pairs long with the sequence TATATA or TATATAA, before the location where transcription is to start. It is called the TATA box and helps position RNA polymerase by marking a point at which transcription begins.

31. The genes in eukaryotes are regulated in a variety of ways by enhancer sequences located before the point at which transcription begins.

32. At these enhancer sequences, different proteins can bind. Some of these DNA binding proteins enhance transcription by opening up tightly packed chromatin or help attract RNA polymerase. Others block access to genes.

33. Why is this regulation important? Eukaryotic gene regulation is complex because of the level of complexity in a multicellular organism. Every cell contains the complete genetic code in their nucleus. Cell specialization requires genetic specialization. Ex. The genes that code for liver enzymes are not going to be expressed in nerve cells.

34. Development and Differentiation When an organism develops, regulation of gene expression is extremely important. Every specialized cell found in the adult develops from the fertilized egg. In embryonic development cells grow and divide and also differentiate. Differentiation – process by which cells become specialized in structure and function

35. Differentiation of cells and tissues in the embryo are controlled by a series of genes called the hox genes. Mutations in these genes can change the organs that develop in specific parts of the body. Ex. Mutations in the hox genes of fruit flies can replace the fly’s antennae with legs growing on its head.

36. The genes that control development are remarkably similar in animals of common ancestors. The common pattern of genetic control exists because all of these genes have descended from the genes of common ancestors. Ex. A gene that controls eye growth in fruit flies is similar to that of the gene that controls eye growth in mice. When a copy of the mouse gene was inserted into the “knee” of the fly an eye grew on its leg. Also, they are similar enough to trade places and still function.