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DNA Biology

DNA Biology. Lab 11. Nucleic Acids. DNA and RNA both built of nucleotides containing Sugar (deoxyribose or ribose) Nitrogenous base (ATCG or AUCG) Phosphate group. Nitrogenous Bases. Nitrogenous bases can be double ringed purines or single ringed pyrimidines. Nitrogenous Bases.

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DNA Biology

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  1. DNA Biology Lab 11

  2. Nucleic Acids • DNA and RNA both built of nucleotides containing • Sugar (deoxyribose or ribose) • Nitrogenous base (ATCG or AUCG) • Phosphate group

  3. Nitrogenous Bases • Nitrogenous bases can be double ringed purinesor single ringed pyrimidines.

  4. Nitrogenous Bases • A purine will always pair with a pyrimidine.

  5. DNA • The phosphate group and sugar make up the backbone of the DNA molecule.

  6. The DNA backbone Phosphate groups and pentose sugars The 5' end of each strand has a free phosphate group attached to the 5' carbon of the pentose sugar. The 3' end has a free hydroxyl group attached to the 3' carbon of the pentose sugar. DNA

  7. DNA • DNA consists of two complementarychains connected by hydrogen bonds. • A=T • C=G

  8. DNA • DNA synthesis occurs in the 5' to 3' direction in both strands. • The DNA strands are antiparallel • 5' end of one is associated with the 3' end of the other. • The DNA ladder is twisted into a double helix • Ten base pairs occur per turn.

  9. RNA • RNAexists as a single polynucleotide chain. • Ribose • Uracil

  10. DNA Replication • DNA must replicate itself prior to cell division. • Enzymes are responsible for each step of replication, including proofreading. • The helix unwinds, separates, and each half acts as a template for the formation of a new complementary strand. • Reaction catalyzed by DNA polymerase.

  11. Gene Expression • Gene expression– the use of information in DNA to direct the production of particular proteins. • Transcription– first stage of gene expression. A messenger RNA (mRNA) is synthesized from a gene within DNA. • Translation– second stage – mRNA is used to direct production of a protein.

  12. DNA Coding • DNA codes for the sequence of amino acids in a protein. • A codonis three base-pairs long and is a segment of mRNA that codes for an amino acid.

  13. Transcription • Messenger RNA (mRNA)transcribes the DNA and transports it out of the nucleus.

  14. Transcription • Before leaving the nucleus, segments of mRNA called intronsare removed and the exonsare spliced together. • Exons contain the information coding for the protein that will be synthesized.

  15. Translation • Translationoccurs on ribosomes outside the nucleus. • mRNA attaches to a ribosome and protein synthesis begins.

  16. Translation • Transfer RNA (tRNA)collects free amino acids from the cytoplasm and delivers them to the polysome(mRNA-ribosome complex) where they are assembled into a polypeptide. • tRNA has a triplet – the anticodon– that is complementary to the codon of mRNA.

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