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Published byStanley Greene Modified over 9 years ago
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Structure Types of RNA Transcription
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=RiboNucleic Acid
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Polymer Single stranded Monomers Nucleotides
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Monomers made of 3 parts each: Phosphate Group Ribose Sugar 1 of 4 nitrogen bases C, A, G, and U! U = Uracil No Thymine!
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Pyrimidine-why? Pairs with adenine
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1. Messenger RNA (mRNA) “Records” information from the DNA in the nucleus and transports it out of the nucleus to the ribosomes
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2. Transfer RNA (tRNA) Delivers amino acids to site of protein synthesis (ribosomes) 3. Ribosomal RNA (rRNA) Helps with ribosome structure; function not entirely understood We will not go into detail on these second 2 until next week!
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DNA is at risk of being damaged if it leaves the nucleus The info in DNA is copied into mRNA mRNA is able to leave nucleus and travel to ribosomes (site of protein synthesis)
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It brings amino acids to ribosomes to form protein strand.
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Transcription 4 Steps (similar to replication) What is different between transcription and DNA replication?
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1. DNA is “unzipped” (HELICASE) 2. Match correct nucleotides according to base pair rules *On only one side of the DNA (RNA POLYMERASE) *U’s not T’s!
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3. Bonding-covalent bonds form between sugar and phosphates *Why don’t the hydrogen bonds remain? 4. Transcription occurs until a “stop sign” is reached and the mRNA strand is complete Transcription Animation
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3 Nitrogen bases represents 1 CODON = 1 AMINO ACID 64 possible codons 3 “stop” codons 61 code for amino acids (20 possibilities) 1 codes to start = AUG = methionine Code is universal – codons represent the same amino acid in all organisms
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Use your codon chart to answer the following: 1. How many different codons code for valine? 2. The codon CGU is for which amino acid? 3. What are the codons for the three “stops”? 4. What are the first 3 amino acids for this strand of mRNA?
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