DNA and ChromosomesGenes are carried by Chromosomes Two plant cells visualized by light microscope, DNA stained with DAPI Chromosome in Cells DNA (deoxyribonucleic acid) AGTC Human 46 chromosomes 22 homologs, x, or x/yThe Structure and Function of DNA Genetic information is carried in the linear sequence of nucleotides in DNA Genetic information contains instructions to synthesize proteins DNA forms double helix with two complimentary strands holding together by hydrogen bonds between A-T (2 bonds) and G-C (3 bonds) DNA duplication occurs using one strand of parental DNA as template to form complimentary pairs with a new DNA strand. DNA is in nucleus in eucaryotes

1953 Watson and Crick determined the structure of DNADNA and its BuildingNucleotides: Guanine (G), Adenine (A), Cytosine (C), Thymine (T).Polarized strand, 5->3Base inside, sugar outside

DNA PairsA always pairs with T, and G with C,A-T two hydrogen bonds, G-C three hydrogen bondsDNA Double Helix10.4 nucleutides/turn; 3.4 nm between nucleutidesDNA to ProteinGenome: the complete set of information in an organisms DNATotal length of DNA about 2 meters long in a human cell, encoding about 30000 proteins

Cell Nucleus, compartmentalized DNA activityNuclear pores allow communicationNuclear lamina and cytoskeleton mechanically support the nucleus

Chromosomal DNA and its Packaging A gene is a nucleotide sequene in a DNA molecule that act as a functional unit for protein production, RNA synthesis. Introns and Exons Chromosome: single long DNA contains a linear array of many genes. Human genome contains 2.3x109 DNA nucleotide pairs, with 22 different autosomes and 2 sex chromosomes. Chromosomal DNA: replication origins, telomeres, centromeres Histones form the protein core for DNA wrapping Nucleosome: repeating array of DNA-protein particles Modification of Chromatin and nucleosomes: histone H1, ATP-driven chromatin remodeling complexes, and enzymatically catalyzed covalent modification of the N-terminal tails of HistonesHuman Chromosome Complex of DNA and protein is called chromatin 44 homologous chromosomes and 2 sex chromosomes Complementary DNA with different Dyes The arrangement of the full chromosome set is called karyotypeBanding Pattern of human chromosomes Giemsa Staining Green line regions: centromeres

Cell CycleDNA molecule not only carries genetic information, but also undergoes conformational changeChromosomes exist through the cycleMitotic and interphase chromosomeSingle chromosome can only be visible during mitosisDNA Molecules are highly condensed in chromosomesNucleosomes of interphase under electron microscopeNucleosome: basic level of chromosome/chromatin organization Chromatin: protein-DNA complexHistone: DNA binding proteinSummary DNA, Chromosome Centromere, telomere, replication origin Nucleosome, Chromatin, Histone: H1, H2A, H2B, H3, H4 Histone octamer, DNA packaging DNA binding proteins, Histone modificationsA model for the structure of a lampbrush chromosome Chromomeres: highly condensed and in general not expressed until unfolding