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VII. DNA and Genome Structure A. Search for the Genetic Information

VII. DNA and Genome Structure A. Search for the Genetic Information B. Determining DNA Structure C. Chromosome Structure. VII. DNA and Genome Structure A. Search for the Genetic Information B. Determining DNA Structure C. Chromosome Structure 1. Eukaryotic Chromosomes.

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VII. DNA and Genome Structure A. Search for the Genetic Information

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  1. VII. DNA and Genome Structure A. Search for the Genetic Information B. Determining DNA Structure C. Chromosome Structure

  2. VII. DNA and Genome Structure A. Search for the Genetic Information B. Determining DNA Structure C. Chromosome Structure 1. Eukaryotic Chromosomes

  3. VII. DNA and Genome Structure A. Search for the Genetic Information B. Determining DNA Structure C. Chromosome Structure 1. Eukaryotic Chromosomes a. DNA wrapped around 8 histone proteins = “nucleosome”… form ‘beads on a string’

  4. VII. DNA and Genome Structure A. Search for the Genetic Information B. Determining DNA Structure C. Chromosome Structure 1. Eukaryotic Chromosomes a. DNA wrapped around 8 histone proteins = “nucleosome”… form ‘beads on a string’ b. 6 nucleosomes are coiled into a ‘solenoid’

  5. VII. DNA and Genome Structure A. Search for the Genetic Information B. Determining DNA Structure C. Chromosome Structure 1. Eukaryotic Chromosomes a. DNA wrapped around 8 histone proteins = “nucleosome”… form ‘beads on a string’ b. 6 nucleosomes are coiled into a ‘solenoid’ c. Supercoiling

  6. VII. DNA and Genome Structure A. Search for the Genetic Information B. Determining DNA Structure C. Chromosome Structure 1. Eukaryotic Chromosomes a. DNA wrapped around 8 histone proteins = “nucleosome”… form ‘beads on a string’ b. 6 nucleosomes are coiled into a ‘solenoid’ c. Supercoiling d. Folding to condensed chromosome

  7. VII. DNA and Genome Structure • A. Search for the Genetic Information • B. Determining DNA Structure • C. Chromosome Structure • 1. Eukaryotic Chromosomes • e. Tightly coiled regions stain dark heterochromatin that often lacks genes. • Lightly staining areas are euchromatin and have a higher density of coding sequences. These can be seen in a ‘polytene chromosome’

  8. VII. DNA and Genome Structure A. Search for the Genetic Information B. Determining DNA Structure C. Chromosome Structure 1. Eukaryotic Chromosomes 2. Bacterial Chromosomes

  9. VII. DNA and Genome Structure A. Search for the Genetic Information B. Determining DNA Structure C. Chromosome Structure 1. Eukaryotic Chromosomes 2. Bacterial Chromosomes - ds-DNA with a few associated proteins similar to histones of eukaryotes.

  10. VII. DNA and Genome Structure A. Search for the Genetic Information B. Determining DNA Structure C. Chromosome Structure 1. Eukaryotic Chromosomes 2. Bacterial Chromosomes - ds-DNA with a few associated proteins similar to histones of eukaryotes. - typically a circular chromosome

  11. VII. DNA and Genome Structure A. Search for the Genetic Information B. Determining DNA Structure C. Chromosome Structure 1. Eukaryotic Chromosomes 2. Bacterial Chromosomes - ds-DNA with a few associated proteins similar to histones of eukaryotes. - typically a circular chromosome - tends to be concentrated around the periphery of a cell - nucleoid

  12. VII. DNA and Genome Structure A. Search for the Genetic Information B. Determining DNA Structure C. Chromosome Structure 1. Eukaryotic Chromosomes 2. Bacterial Chromosomes 3. Mt-DNA and Cp-DNA - Mitochondria and chloroplasts have their own DNA that is very similar to bacteria DNA in structure (circular with few proteins) and sequence (no introns, repeats). Mt-DNA from a frog cell mitochondrion.

  13. VII. DNA and Genome Structure A. Search for the Genetic Information B. Determining DNA Structure C. Chromosome Structure 1. Eukaryotic Chromosomes 2. Bacterial Chromosomes 3. Mt-DNA and Cp-DNA 4. Viral Chromosomes ss or ds DNA or RNA small

  14. VII. DNA and Genome Structure A. Search for the Genetic Information B. Determining DNA Structure C. Chromosome Structure D. Genome Structure

  15. VII. DNA and Genome Structure A. Search for the Genetic Information B. Determining DNA Structure C. Chromosome Structure D. Genome Structure 1. viruses

  16. VII. DNA and Genome Structure A. Search for the Genetic Information B. Determining DNA Structure C. Chromosome Structure D. Genome Structure 1. viruses (103 – 106) Small genomes because viruses rely on the metabolism of their host cell; they are cellular/genetic parasites.

  17. VII. DNA and Genome Structure A. Search for the Genetic Information B. Determining DNA Structure C. Chromosome Structure D. Genome Structure 1. viruses (103 – 106) Small genomes because viruses rely on the metabolism of their host cell; they are cellular/genetic parasites. Many viruses have introns – intervening sequences in their genes that are spliced out after transcription. They have been spliced from eukaryotic genomes. They are often transposons, too.

  18. D. Genome Structure 1. viruses 2. Eubacteria/Archaea (105 – 106)

  19. D. Genome Structure 1. viruses 2. Eubacteria/Archaea

  20. D. Genome Structure 1. viruses 2. Eubacteria/Archaea (105 – 106) - again, parasitic forms are generally the smallest - protein genes do not have introns (non-coding sequence in genes) - only t-RNA and r-RNA genes have introns (Archaea); not protein-encoding genes

  21. D. Genome Structure 1. viruses 2. Eubacteria/Archaea 3. Eukaryotes (107 – 1011) Again, organelles and other obligate symbionts have very reduced genomes because they rely on their host’s metabolism.

  22. D. Genome Structure 1. viruses 2. Eubacteria/Archaea 3. Eukaryotes The amount of DNA DOES NOT correlate with the complexity of the organism… this is called the c-value paradox. Why? What does the EXTRA DNA in some simple organisms do??

  23. D. Genome Structure 1. viruses 2. Eubacteria/Archaea 3. Eukaryotes The amount of DNA DOES NOT correlate with the complexity of the organism… this is called the c-value paradox. Why? What does the EXTRA DNA in some simple organisms do?? Actually, it may do nothing – it may be highly repetitive DNA (transposons)

  24. D. Genome Structure 1. viruses 2. Eubacteria/Archaea 3. Eukaryotes Types of DNA: - single copy sequences: functional genes and pseudogenes (vestigial genes) - repetitive DNA ONLY 1-10% of a eukaryotic genome codes for protein; most serves no know function!!

  25. Repetitive DNA: - Highly Repetitive DNA – typically concentrated in heterochromatic regions such as the centromere and telomere.

  26. Repetitive DNA: - Highly Repetitive DNA – typically concentrated in heterochromatic regions such as the centromere and telomere. There are repeated sequences consisting of 2 bases (‘tandem’ repeats) like GGATGGAT that may occur 1000’s of times in a row in these areas.

  27. Repetitive DNA: - Highly Repetitive DNA – typically concentrated in heterochromatic regions such as the centromere and telomere. Tandem repeated sequences are repeated as immediate neighbors like GGATGGAT that may occur 1000’s of times in a row in these areas. - Moderately Repetitive DNA: There are Variable Number Tandem Repeats (VNTR’s) that are within (intronic) and between genes and are 10-100 bp long.

  28. Repetitive DNA: - Highly Repetitive DNA – typically concentrated in heterochromatic regions such as the centromere and telomere. Tandem repeated sequences are repeated as immediate neighbors like GGATGGAT that may occur 1000’s of times in a row in these areas. - Moderately Repetitive DNA: There are Variable Number Tandem Repeats (VNTR’s) that are within (intronic) and between genes and are 10-100 bp long. Short Tandem Repeats (STR’s) are 25 bp long, and have 5-50 repeats. The number of repeats in VNTR’s and STR’s varies among individuals, and is the basis of DNA fingerprinting.

  29. Repetitive DNA: - Highly Repetitive DNA - Moderately Repetitive DNA - Transposons: Short sequences that have millions of copies throughout the genome (not repeated in sequence). Also, they COPY THEMSELVES and insert their copies elsewhere in the genome!

  30. Repetitive DNA: - Highly Repetitive DNA - Moderately Repetitive DNA - Transposons: Short sequences that have millions of copies throughout the genome (not repeated in sequence). Also, they COPY THEMSELVES and insert their copies elsewhere in the genome! i. Short Interspersed Elements (SINE): 100-500 bp, present millions of times. Alu sequence in humans comprises 5% of the genome – more than coding sequence!!

  31. Repetitive DNA: - Highly Repetitive DNA - Moderately Repetitive DNA - Transposons: Short sequences that have millions of copies throughout the genome (not repeated in sequence). Also, the COPY THEMSELVES and insert their copies elsewhere in the genome! i. Short Interspersed Elements (SINE): 100-500 bp, present millions of times. Alu sequence in humans comprises 5% of the genome – more than coding sequence!! ii. Long Interspersed Elements (LINE): 6kb long, present 100,000 times. L1 in humans codes for a reverse transcriptase that makes a DNA copy that is inserted elsewhere. Also called retrotransposons.

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