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Chromosome Structure and DNA Sequence Organization

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Relatively simple DNA molecules. less complex than ... Mitochondria and Chloroplasts ... of sequences independent addition of chloroplasts and mitochondria ... – PowerPoint PPT presentation

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Title: Chromosome Structure and DNA Sequence Organization


1
Chapter 11
  • Chromosome Structure and DNA Sequence
    Organization

2
Viral and Bacterial Chromosomes
  • Relatively simple DNA molecules
  • less complex than eukaryotes
  • Single nucleic acid molecule, no associated
    proteins like histones
  • Little genetic information

3
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4
Viral Chromosomes
  • Either DNA or RNA
  • Single or double stranded
  • Usually contained in a protein head structure
  • Circular dsDNA in bacteriophage ?

5
(No Transcript)
6
Phage T2
  • DNA and viral protein
  • Most of the space in the head is occupied by
    nucleic acid
  • Nucleic acids of viruses are functionally inert
    until introduced back into a host cell

7
Bacterial DNA
  • ds DNA packed into a nucleoid region
  • Relatively simple and doesnt take up the whole
    cell
  • Several DNA binding proteins involved HU and H1
  • positively charged AA bind to the negatively
    charged DNA
  • similar to histones but do not function in
    packaging
  • DNA is active and transcribed and replicated

8
Mitochondria and Chloroplasts
  • DNA similar to bacteria and viruses, different
    than the nuclear DNA in the cell
  • Have own DNA and genetic system to express the
    information
  • remember can influence the phenotype and cause
    disease (Chapter 4)
  • Arose from free-living prokaryotes that did
    aerobic respiration and photosynthesis
  • endosymbiotic theory prokaryotes are engulfed
    by primitive large cell without bioenergetic
    functions, symbiotic relationship occurs and
    eventually loose the ability to live independently

9
mtDNA
  • dsDNA, replicates semiconservatively, no
    chromosomal proteins
  • Size of DNA varies on organism and copies
  • Appear to have no introns or repetitive sequences
  • Use several modification of genetic code
  • Requires nuclear DNA gene products to replicate
    mtDNA

10
Human mtDNA
  • Contains 2 rRNA, 22 tRNA and numerous polypeptide
    genes for cellular respiration remainder comes
    from nuclear DNA
  • Ribosomes are different from cytoplasmic ones,
    usually in S close to bacterial ribosomes
  • Nuclear coded genes for DNA replication and
    transcription
  • DNA/RNA pol, initiation/elongation factors,
    ribosomal proteins, aminoacyl tRNA synthetase
  • distinct from cytoplasmic things
  • pol is sensitive to antibiotics like bacteria

11
Mitochondrial and Cellular Components
12
cpDNA
  • Autonomous genetic system DNA and complete
    protein synthesis apparatus jointly form
    chloroplast and nuclear DNA
  • Much larger than mtDNA, similar in DNA in
    bacteria
  • Circular dsDNA, semiconservative, free of
    associated proteins
  • Many copies in the chloroplast
  • Some gene products function during translation

13
Higher Plant Chloroplasts
  • 2 copies of genes encoding 5S, 16S and 23S rRNA,
    25 tRNA genes, number of ribosome proteins
    specific to cp-ribosomes
  • ribosomes are part cp and nuclear gene products
  • cpDNA has genes for photosynthesis process
    small subunit of ribulose-1-5-bisphosphate
    carboxylase by nuclear DNA and large subunit by
    cpDNA
  • cpDNA has non-coding regions and duplications of
    sequences independent addition of chloroplasts
    and mitochondria
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