GEN 3000- Chapter 11 Notes
GEN 3000- Chapter 11 Notes GEN 3000
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This 2 page Class Notes was uploaded by Jomary Arias on Friday February 26, 2016. The Class Notes belongs to GEN 3000 at Clemson University taught by Dr. Kate Tsai in Spring 2016. Since its upload, it has received 61 views. For similar materials see Genetics in Biomedical Sciences at Clemson University.
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Date Created: 02/26/16
Genetics 3000 Kate Tsai Chapter 11: DNA Organization Key Terms Primary Structure- nucleotide sequence (A-T, G-C) Secondary Structure- double stranded helix Tertiary Structure- higher order packing Super coiling- either adding more spins (over rotating) or unraveling DNA and taking away spins (under rotation) Positive Supercoil- add rotations Negative Supercoil- remove rotations Chromatin- complex of DNA and proteins in eukaryotic chromosomes, contain histones Scaffolding Proteins- non-histone, play a role in folding and packing Nuclease- cuts DNA, resulting in multiple fragments identical in size Linker DNA- combines core histones of nucleosome to chromatin known as “beads-on- a-string” Nucleosome- two copies of H2A, H2B, H3, and H4 +DNA Histone tails- targets for binding Acetylation- neutralizes positive charge and relaxes histone hold Methylation and phosphorylation- gives the histone hold strength and becomes heterochromatin Polytene Puff- region of polytene chromosome that is relaxed and pulled out using chromatin remodeling. Allows access to DNA Lampbrush Chromosome- mitotic chromosome, allows crossing over to take place while the DNA is compacted Centromere- region of chromosome where spindle fibers attach CEN region- critical for sequences within the centromere region Telomeres- maintain ends of chromosomes Transcribed regions- TERRA (telomeric repeat-containing RNA) contribute to methylation Prokaryotes - Most DNA is negatively supercoiled - Naked DNA - Separation of strands is easier, occupies less space than relaxed - Bacterial DNA is packaged with proteins not histones Eukaryotes - DNA always interacting with proteins - Half of protein mass is non-histone chromosomal proteins( scaffolding proteins and - DNA replication) Genetics 3000 Kate Tsai Chapter 11: DNA Organization Heterochromatin Euchromatin Highly condensed chromatin, inactive X Chromatin can be transcriptionally active, Ex) Teleomere, centromere functional DNA known as “open” chromatin Chromatin Remodeling - Structure must change to allow access to DNA, allows you to - Involves: Histone Tails, Acetylation, Methylation and phosphorylation - Remodel histone proteins, then use acetylation to allow protein arms to release DNA strand. The positive charge of the arms is neutralized by the negatively charged DNA and the arms relax. Chromosome Banding - Staining of chromosomal regions - Helps identify translocations, inversions, and duplication with in chromosomes - Allows us to name areas on the chromosome (A-T, G-C) - Similar to finger prints. - R banding and Q banding are common types of banding - Chromosomes can also be identified by staining the centromere Centromeres - Necessary for chromosomal segregation - Region of chromosome where spindle fibers attach - Without one, the chromosome is lost - 2 types of centromeres: Point centromere Regional centromere Small, precise centromere region. Very Most plants and animals repetitive within centromere. Telomeres Function: 1. Structural- serves as a cap to blocj unraveling 2. Replication of ends a) Generally does not occur to somatic cells because it degrades over multiple round of replication, it is shortened to death b) Single-celled organism and germ cells do have to deal with this
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