2. 1. 5 carbon sugar- deoxyribose 2. Phosphate group 3. Nitrogen bases- A T G C (adenine, thymine, guanine, cytosine)

3. Similar to DNA, except… Sugar is ribose Single stranded Uracil (U) instead of Thymine (T)

4. Messenger RNA (mRNA) – carries copies of instructions for making proteins Ribosomal RNA (rRNA) – makes up ribosomes Transfer RNA (tRNA) – transfers specific amino acids to the ribosome according to instructions.

5. Carries DNA message from nucleus to cytoplasm mRNA reads the message in “triplets” called codons 64 different codons code for 20 different amino acids 1 start codon- AUG 3 stop codons- UUA, UAG, UGA

6. * Responsible for Transcription- copying the DNA code in the nucleus Code- universal to all life= evidence for common ancestry Redundancy or “wobble”- codons for same amino acid can differ in 3 rd base ( a relaxing of the base-pairing rule in the tRNA )

7. * Promotor- initiates transcription- DNA polymerase attaches Terminator- sequence that signals the end of transcriptor The direction of transcription is known as “downstream” and “upstream” Promotor sequence- upstream from terminator The stretch of DNA that is transcribed is the transcription unit

8. 1. Elongation 2. Termination 3. Initiation

9. Start Codon- AUG- methionine Once polymerase is attached to the promoter DNA, the 2 strands unwind, and the enzyme starts transcribing the template strand promotor- start point- extends several dozen nucleotide pairs upstream from start point

10. RNA polymerase continues to move along DNA and untwist the helix, exposing 10-20 DNA base pairs. Adds nucleotides to 3’ end of the growing RNA molecule DNA re-forms and new RNA molecule pulls away from its DNA template About 60 nucleotides/second

11. Transcription ends after RNA polymerase transcribes the terminator (stop codon) Continues past terminator signal (AAU AAA) Cuts loose Stop codons= UAA, UAG, UGA

12. Initiator  Elongation  Termination Promotor Start Codon RNA Polymerase Unzips Copies Zips back up Continues past terminator signal (AAUAAA) Cuts loose

15. The sequence of DNA nucleotides that codes for a eukaryotic polypeptide is NOT continuous! There are non-coding segments that lie between coding segments called intervening segments. ( Introns)

16. *Introns- long segments of non-coding base sequences Exons- coding regions- expressed in protein synthesis. The leader & trailer RNA are not translated Introns are removed & are exons joined before the mRNA leaves nucleus—this is called RNA splicing. Signals for splicing are called sn(RNP’s) or “snurps”

17. *removal of portion of RNA *about 8000 nucleotides & only 1200 needed for avg. sized protein of 400 amino acids *there are long stretches of non-coding nucleotide regions that are not translated & they are mixed between coding segments. Introns- non-coding segments Exons- coding segments Introns are cut out and exons move to cytoplasm for translation

18. snRNP’s- (“snurps”)- small nuclear ribonuclear proteins that are signals for RNA splicing. Spliceosome- responsible for actual splicingof introns & rejoining of exons. Ribozymes- RNA molecule that functions as an enzyme. Functions as a catalyst.

19. Carried out by tRNA They are specific for the amino acids they carry Have a specific base triplet (anti-codon)-that is complimentary to the mRNA codon 61 codons for amino acids can be read from mRNA; but only 45 tRNA molecules. That is where Wobble come into effect Wobble enables 3 rd nucleotide of some tRNA anti-codons to pair w/more than 1 kind of base in a codon.

20. 1 tRNA can recognize more than 1 mRNA codon A modified base inosine (I) is the 3 rd position and can pair w/ U,C,A Example: tRNA CCI anti-codon can bind to mRNA GGU, GGC, or GGA Aminoacyl-tRNA synthetase- joins amino acid to tRNA The phosphate ion is what gives DNA and RNA the acidic property.