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RNA

RNA. Ribonucleic Acid. Ribonucleic Acid (RNA). RNA is much more abundant than DNA There are several important differences between RNA and DNA: - the pentose sugar in RNA is ribose, in DNA it’s deoxyribose - in RNA, uracil replaces the base thymine (U pairs with A)

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RNA

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  1. RNA Ribonucleic Acid

  2. Ribonucleic Acid (RNA) • RNA is much more abundant than DNA • There are several important differences between RNA and DNA: - the pentose sugar in RNA is ribose, in DNA it’s deoxyribose - in RNA, uracil replaces the base thymine (U pairs with A) - RNA is single stranded while DNA is double stranded - RNA molecules are much smaller than DNA molecules)

  3. Structure of RNA • Single stranded • Ribose Sugar • 5 carbon sugar • Phosphate group • Adenine, Uracil, Cytosine, Guanine

  4. Types of RNA • Three main types • Messenger RNA (mRNA) – transfers DNA code to ribosomes for translation. • Transfer RNA (tRNA) – brings amino acids to ribosomes for protein synthesis. • Ribosomal RNA (rRNA) – Ribosomes are made of rRNA and protein.

  5. Transcription • RNA molecules are produced by copying part of the nucleotide sequence of DNA into complementary sequence in RNA, a process called transcription. • During transcription, RNA polymerase binds to DNA and separates the DNA strands. RNA polymerase then uses one strand of DNA as a template from which nucleotides are assembled into a strand of mRNA.

  6. mRNA

  7. How Does it Work? • RNA Polymerase looks for a region on the DNA known as a promoter, where it binds and begins transcription. • RNA strands are then edited. Some parts are removed (introns) - which are not expressed – and other that are left are called exons or expressed genes.

  8. The Genetic Code • This is the language of mRNA. • Based on the 4 bases of mRNA. • “Words” are 3 RNA sequences called codons. • The strand aaacguucgccc would be separated as aaa-cgu-ucg-ccc the amino acids would then be Lysine – Arginine – Serine - Proline

  9. Genetic Codes

  10. Translation • During translation, the cell uses information from messenger RNA to produce proteins. • A – Transcription occurs in nucleus. • B – mRNA moves to the cytoplasm then to the ribosomes. tRNA “read” the mRNA and obtain the amino acid coded for. • C – Ribosomes attach amino acids together forming a polypeptide chain. • D – Polypeptide chain keeps growing until a stop codon is reached.

  11. Protein Synthesis • The two main processes involved in protein synthesis are - the formation of mRNA from DNA (transcription) - the conversion by tRNA to protein at the ribosome (translation) • Transcription takes place in the nucleus, while translation takes place in the cytoplasm • Genetic information is transcribed to form mRNA much the same way it is replicated during cell division

  12. Translation to Protein

  13. Mutations • Gene mutations result from changes in a single gene. Chromosomal mutations involve changes whole chromosomes.

  14. Gene Mutation • Point Mutation – Affect one nucleotide thus occurring at a single point on the gene. Usually one nucleotide is substituted for another nucleotide. • Frameshift Mutation – Inserting an extra nucleotide or deleting a nucleotide causes the entire code to “shift”.

  15. Gene Mutation

  16. Chromosomal Mutations • Deletion – Part of a chromosome is deleted • Duplication – part of a chromosome is duplicated • Inversion – chromosome twists and inverts the code. • Translocation – Genetic information is traded between nonhomologous chromosomes.

  17. Chromosomal Mutations

  18. Mutations

  19. More Mutations

  20. Gene Regulation • In simple cells (prokaryotic) lac genes which are controlled by stimuli, turn genes on and off. • In complex cells (eukaryotic) this process is not as simple. Promoter sequences regulate gene operation.

  21. Review

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