Chromosomes and Chromatin – Flashcards

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chromosome
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the vehicle that ensures stable maintenance of the genetic info and facilitates its transmission to the next generation. Contains one double-stranded DNA molecule.
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cell cycle
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series of events that lead to the replication and segregation of chromosomal DNA during cell division.
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chromatin
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protein-DNA complex that packages eukaryotic DNA
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intergenic DNA
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does not contain genes
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ploidy
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how many sets of identical chromosomes a cell contains
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diploid
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contains two copies of each chromosome
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haploid
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contains one set of chromosomes
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homologous
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the copy of each chromosome inherited from the mother is homologous to the copy inherited from the father ( it contains the same genes and gene order but different versions of each gene).
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Polyploid
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cell which contain multiple sets of chromosomes.
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plasmids
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double-stranded, circular DNA molecules
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G1 phase
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(gap phase I), cell growth occurs until cells attain a minimum size that is required to progress to the next phase.
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S phase
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(DNA synthesis) the DNA is copied, thereby duplicating all of the chromosomes.
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sister chromatids
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two identical copies of each chromosome
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G2 phase
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(gap phase 2), the cell prepares for mitosis
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M phase
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Mitotic Phase, sister chromatids are separated and a complete set of chromosomes is delivered to each pole of the cell.
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interphase
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when changes in chromosome and nuclear structures during mitosis are clearly evident int eh microscope.
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cytokinesis
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completes the division of the mother cell into two daughter cells (with the same number of chromosomes)
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nucleoid
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the compacted bacterial chromosome
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histones
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the basic DNA-binding proteins that package DNA into chromatin
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nucleosome
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the fundamental unit of eukaryotic chromatin
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euchromatin
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relatively decondensed regions of DNA
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heterochromatin
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more compacted regions
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telomeres
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special DNA sequences at the ends of chromosomes
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nuclease sensitivity
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heterochromatin is more resistant to digestion by DNase I than euchromatin. This could be because heterochromatin is more condensed or because the nuclease reacts different with DNA bound by specific heterochromatin proteins.
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Origin of replication
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a location in the chromosome at which DNA replication begins
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acetylation
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removes the positive charge from lysine side chains and thereby alters interactions with the negatively charged DNA. Generates sites for the bonding of proteins containing domains known as bromodomains.
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histone modifications
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an important means of modulating any process that involves accessing the DNA. They are reversible.
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Histone acetyltransferases (HATs)
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covalently attach acetyl groups to lysine side chains. Actively transcribed regions in euchromatin contain highly acetylated histones
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Histone Deacetylases (HDACs)
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remove the acetyl group.
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bromodomains
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bind specifically to particular acetyl-lysines. Then recruits other proteins, including nucleosome remodeling complexes or other enzymes that act on DNA
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Histone methyltransferases (HMTs)
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methylate enzymes
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histone demethlylases
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remove methyl groups
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Chromodomains
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bind to specific methylated lysines. typically found in proteins that mediate transcriptional silencing
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ATP-denpendent nucleosome-remolding complexes
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multisubunit enzyme complexes that use the energy provided by ATP hydrolysis to change the positions of nucleosomes on DNA. Can either slide the histone octamer along the DNA or remove the histone octamer entirely and transfer it from one segment of the DNA molecule to another.
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