C … ontents and L … anguage I … ntegrated L … earning

2. C…ontents and L…anguage I …ntegrated L …earning

3. CLIL : links https://youtu.be/uIRZWn7-x2Y https://youtu.be/7QOPHRHJvPc https://youtu.be/ssPbrPpuXbI (....ifyouwanttoknowsomething more aboutCLIL……….) 1 2 3

4. “Our”CLILExperience School: Liceo Scientifico “A. Scacchi” Class: 5^ H 2018-19 VehicularLanguage: English Subject : Chemistry Topic : Biomolecules Contents: FunctionsofNucleicAcids Teachers : Antonia Panebianco Elisabetta Casamassima

5. FUNCTIONSOFNUCLEICACIDS • DNA carries information and isexpressedthrough RNA • DNA isusuallycompletelyreplicatedbutonlypartiallytranscribed • RNA transcripts are producedfromgenesthat code forspecificproteins (Central Dogma) • Transcriptionofdifferentgenesoccurs at differenttimes and, in multicellularorganisms, in differentcellsof the body

6. DNA structure and replication • DNAisa purelyinformationalmolecule • DNA information isencoded in the sequenceofbasescarried in itsstrands • DNA can bereproducedexactly • ThisprocessisDNA replication. Itisdonebypolymerization (condensation) usinganexistingstrandas a base-pairingtemplateandspecificenzymes https://www.youtube.com/watch?v=9kp9wiYMQUU https://www.youtube.com/watch?v=8kK2zwjRV0M https://www.youtube.com/watch?v=eM7arWJJ3zk

7. Mechanisms of DNA Damage and Repair • The DNA base sequencerevealsevolutionaryrelationships: howisitpossible? • DNA carrieshereditary information fromone generation to the next, graduallyaccumulatingchanges in its base sequenceover long periodsoftime. • This, in spiteof the mechanismsof DNA repair https://www.youtube.com/watch?v=sX6LncNjTFU

8. DNA Transcription and Translation

9. DNA Transcription • Information coded in the sequenceof nucleotide bases in DNA ispassedtoa sequenceofnucleotide bases in RNA https://www.khanacademy.org/.../transcription.../overview-of-transcription https://www.youtube.com/watch?v=bKIpDtJdK8Q&t=3s

10. Stagesoftranscription 1-Initiation. RNA polymerase binds to a sequence of DNA called the promoter, found near the beginning of a gene. Each gene (or group of co-transcribed genes, in bacteria) has its own promoter. Once bound, RNA polymerase separates the DNA strands, providing the single-stranded template needed for transcription.

11. Stagesoftranscription 2-Elongation.One strand of DNA, the template strand, acts as a template for RNA polymerase. As it "reads" this template one base at a time, the polymerase builds an RNA molecule out of complementary nucleotides, making a chain that grows from 5' to 3'. The RNA transcript carries the same information as the non-template (coding) strand of DNA, but it contains the base uracil (U) instead of thymine (T).

12. Stagesoftranscription 3-Termination.Sequences called terminators signal that the RNA transcript is complete. Once they are transcribed, they cause the transcript to be released from the RNA polymerase. An example of a termination mechanism involving formation of a hairpin in the RNA is shown below.

13. Eukaryotic RNA modifications • In eukaryotes, the transcript of a protein-coding gene is called a pre-mRNAand must go through extra processing before it can direct translation. • Eukaryotic pre-mRNAs must have their ends modified, by addition of a 5' cap (at the beginning) and 3' poly-A tail (at the end). • Many eukaryotic pre-mRNAs undergo splicing. In this process, parts of the pre-mRNA (called introns) are chopped out, and the remaining pieces (called exons) are stuck back together.

14. Eukaryotic RNA modifications • Many eukaryotic pre-mRNAs undergo splicing. In this process, parts of the pre-mRNA (called introns) are chopped out, and the remaining pieces (called exons) are stuck back together. End modifications increase the stability of the mRNA, while splicing gives the mRNA its correct sequence. (If the introns are not removed, they'll be translated along with the exons, producing a "gibberish" polypeptide.) To learn more about pre-mRNA modifications in eukaryotes, check out the article on pre-mRNA processing.

15. Translationprocess Key termsMeaning RNA (ribonucleic acid) Single-strandednucleic acid thatcarries out the instructionscoded in DNA Central dogma ofbiologyThe processbywhich the information in genes flowsintoproteins: DNA → RNA → protein Polypeptide A chainof amino acids Codon A sequenceofthreenucleotidesthat correspondswith a specific amino acid or start/stop signalduringtranslati TranscriptionProcessduringwhich a DNA sequenceof a gene iscopiedtomake a RNA molecule TranslationProcessduringwhichanmRNAmoleculeis usedtoassemble amino acidsintopolypeptide chains Mutation A change in a geneticsequence https://www.khanacademy.org/science/biology/gene-expression-centraldogma/translation

16. Typesof RNA TypeRole Messenger RNA (mRNA) Carries information from DNA in the nucleus to ribosomes in the cytoplasm Ribosomal RNA (rRNA) Structural component of ribosomes Transfer RNA (tRNA) Carries amino acids to the ribosome during translation to help build an amino acid chain

17. The genetic code The four bases of RNA form a language with just four nucleotide bases: adenine (A), cytosine (C), guanine (G), and uracil (U). The genetic code is read in three-base words called codons. Each codon corresponds to a single amino acid (or signals the starting and stopping points of a sequence).

18. Translationprocess In translation, the sequence of the mRNA is decoded to specify the amino acid sequence of a polypeptide. The name translation reflects that the nucleotide sequence of the mRNA sequence must be translated into the completely different "language" of amino acids.

19. Stagesoftranslation • Translation involves “decoding” a messenger RNA (mRNA) and using its information to build apolypeptide, or chain of amino acids. • For most purposes, a polypeptide is basically just a protein (with the technical difference being that some large proteins are made up of several polypeptide chains).

20. Codonsto amino acids • In translation, the codons of an mRNA are read in order (from the 5' end to the 3' end) by molecules called transfer RNAs, or tRNAs. • Each tRNA has an anticodon, a set of three nucleotides that binds to a matching mRNA codon through base pairing. The other end of the tRNA carries the amino acid that's specified by the codon.

21. Stagesoftranslation In an mRNA, the instructions for building a polypeptide come in groups of three nucleotides called codons. Here are some key features of codons to keep in mind as we move forward: • There are 61 different codonsfor amino acids • Three “stop” codonsmark the polypeptide as finished • One codon, AUG, is a “start” signal to kick off translation (it also specifies the amino acid methionine) • These relationships between mRNA codons and amino acids are known as the genetic code

22. Initiation In order for translation to start, we need a few key ingredients. These include: • A ribosome (which comes in two pieces, large and small) • An mRNA with instructions for the protein we'll build • An "initiator" tRNA carrying the first amino acid in the protein, which is almost always methionine(Met) • During initiation, these pieces must come together in just the right way. Together, they form the initiation complex, the molecular setup needed to start making a new protein.

23. Initiation Inside the cells of other eukaryotes, translation initiation goes like this: 1- first, the tRNA carrying methionine attaches to the small ribosomal subunit. Together, they bind to the 5' end of the mRNA by recognizing the 5' GTP cap (added during processing in the nucleus). 2- Then, they "walk" along the mRNA in the 3' direction, stopping when they reach the start codon(often, but not always, the first AUG).

25. Initiation in procariotics In bacteria, the situation is a little different. Here, the small ribosomal subunit doesn't start at the 5' end of the mRNA and travel toward the 3' end. Instead, it attaches directly to certain sequences in the mRNA.

26. Elongation The first, methionine-carrying tRNA starts out in the middle slot of the ribosome, called the P site. Next to it, a fresh codon is exposed in another slot, called the A site. The A site will be the "landing site" for the next tRNA, one whose anticodon is a perfect (complementary) match for the exposed codon.

27. Elongation

28. Elongation • Once the matching tRNA has landed in the A site, it's time for the formation of the peptide bond that connects one amino acid to another. This step transfers the methionine from the first tRNA onto the amino acid of the second tRNA in the A site. • The methionine forms the N-terminus of the polypeptide, and the other amino acid is the C-terminus. • Once the peptide bond is formed, the mRNA is pulled onward through the ribosome by exactly one codon. This shift allows the first, empty tRNAto drift out via the E ("exit") site. It also exposes a new codon in the A site, so the whole cycle can repeat. • And repeat it does...from a few times up to a mind-boggling 33,33,33, comma000000000 times! The protein titin, which is found in your muscles and is the longest known polypeptide, can have up to 33,33,33, comma000000000 amino acids.

29. Termination • Translation ends in a process called termination. Termination happens when a stop codon in the mRNA (UAA, UAG, or UGA) enters the A site. • Stop codons are recognized by proteins called release factors, which fit neatly into the P site (though they aren't tRNAs). Release factors mess with the enzyme that normally forms peptide bonds: they make it add a water molecule to the last amino acid of the chain. This reaction separates the chain from the tRNA, and the newly made protein is released. https://www.youtube.com/watch?v=ocAAkB32Hqs https://www.khanacademy.org/science/biology/gene-expression-central-dogma/translation-polypeptides/v/translation-mrna-to-protein29