1 / 25

DNA, RNA & PROTEINS

DNA, RNA & PROTEINS. The molecules of life. DNA. Deoxyribonucleic Acid (DNA) is the blueprint for life:. DNA structure. DNA is a polymer of nucleotides Each nucleotide composed of _________________ _________________ _________________. Four DNA bases.

fkruse
Download Presentation

DNA, RNA & PROTEINS

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. DNA, RNA & PROTEINS The molecules of life

  2. DNA • Deoxyribonucleic Acid (DNA) • is the blueprint for life:

  3. DNA structure • DNA is a polymer of nucleotides Each nucleotide composed of __________________________________ _________________

  4. Four DNA bases • Four kinds of nitrogenous bases: • Purine bases • Pyrimidine bases

  5. DNA: Complimentary base pairing • Adenine pairs with ________ A • Cytosine pairs with _________ C

  6. DNA STRUCTURE • DNA is a ________ helix • Discovered by Watson and Crick

  7. DNA REPLICATION (in the nucleus)

  8. RNA structure and synthesis • RNA: RIBONUCLEIC ACID • Is very similar to DNA (repeating subunits, nucleotides). • Difference between RNA and DNA: 1. Each nucleotide contains a different sugar: RIBOSEinstead of deoxyribose. 2. Bases are A, G, C, and U (URACIL) A pairs with U; G pairs with C

  9. RNA 3. RNA is single stranded and shorter

  10. CENTRAL DOGMA transcription DNA RNA Proteins • 3 different RNA molecules involved in protein synthesis: mRNA (messenger RNA) rRNA (ribosomal RNA tRNA (transfer RNA) translation

  11. PROTEIN SYTNESIS • 1 step: Transcription occurs in the nucleus • 2 step: Translation occurs in the cytoplasm

  12. 1st stepTranscription: DNA  RNA • Transcription occurs in the nucleus First: DNA unwinds in a section Next: mRNA (messenger RNA) is formed by base pairing with the parent strand of DNA. This begins transcription. Then: mRNA carries the message about what type of protein to make from the DNA in the nucleus to the ribosome

  13. Transcription • Once mRNA is formed, enzymes in the nucleus remove the Introns (noncoding message) and leave the Exons (good message)

  14. The Genetic Code • Each 3 consecutive bases on the mRNA is a code word, CODON, that specifies an amino acid. • The genetic code consists of 64 codons, • but only 61 code amino acids. • Three codons act as signal to stop the process • One codon, AUG, codes for methionine, and is also the Start signal for translation.

  15. 2nd stepTranslation: RNA  Protein • Translation: synthesizing a code from amino acids, according to the sequences of the nucleotides in mRNA. • Occurs at the ribosome, in cytoplasm of cell • Ribosomal RNA, rRNA, is needed for protein synthesis – helps mRNA bind to the ribosome • tRNA, brings specific amino acids to the ribosome to be assembled as proteins.

  16. Translation • Ribosomes are the sites of ______________

  17. Transfer RNA (tRNA) • Transport molecule that carries specific amino acid to a ribosome • Each tRNA recognizes the correct codon on the mRNA molecule

  18. Translation

  19. Steps in Translation • mRNA leaves the nucleus and migrates to ribosome • mRNA binds to small ribosomal subunit • tRNA brings an amino acid to the ribosome, where anticodon on the tRNA binds to the codon of the mRNA • The amino acid bonds to its adjoining amino acid to form a growing polypeptide molecule • The tRNA without the amino acid is released from the ribosome • Other tRNA’s bring amino acids to the ribosome to complete the protein molecule

  20. Protein translation

  21. Protein synthesis • Occurs in the cytoplasm of the cell

  22. Summary:

  23. Important • Both DNA and RNA have a direction: one end is the 3’ the other is the 5’ end. • Thus, codons are read in one direction only. • Also, note there is redundancy in the genetic code: the different sequences can specify for the same amino acid. Example: _______________= Leucine

  24. When things go wrong… • Mutations: changes in the DNA sequence, that may be passed along to future generations. • Point mutations: a single base substitution THE CAT SAW THE RAT THE CAT SAW THE HAT • Deletion: a small DNA segment is lost • Insertion: a segment of DNA is added • Frame-shift mutation: modification of the reading frame after a deletion or insertion, resulting in all codons downstreams being different.

  25. Somatic Mutations • ___________ mutations: occur in body cells, or cells that do not lead to gametes. • Somatic mutations that occur in leaves, roots or stems are usually not passed on to future generations… • UNLESS the plant reproduces ____________

More Related