Biology 1100 Lecture 13 And 14 Notes
Biology 1100 Lecture 13 And 14 Notes Bio 1100
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This 4 page Class Notes was uploaded by Kyle Edward Davis on Saturday April 9, 2016. The Class Notes belongs to Bio 1100 at East Carolina University taught by Dr. Rao in Spring 2016. Since its upload, it has received 15 views. For similar materials see Principles Of Biology in Biology at East Carolina University.
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Date Created: 04/09/16
Lecture 13 and 14 notes Chapter 13: Meiosis Chromosomes: Homologous chromosomes: chromosomes that are the same size, have the same genes, and shape but have different version of genes(alleles) Karotypes: Number and types of chromosomes present in organisms Sex Chromosomes: Determine sex of individual Autosomes: Other chromosomes Humans have 46 chromosomes 22 autosome pairs and 2 sex chromosomes Ploidy: Indicates the number of each type of chromosomes present Haploid: One of each type of chromosome Diploid: Two of each type of chromosome o Have paternal and maternal chromosome Polyploid: three or more types of chromosomes Meiosis 1 1. Early prophase: Homologous chromosomes come together to form tetrads or bivalents and a process called synapsis (bringing together of non-sister chromosomes) takes place i. Process forms synaptonemal complex(network of proteins that connect homologous chromosomes) 2. Late prophase: non-sister chromatids(chromatids belonging to homologous chromosomes) separate at many points in length but stay connected at chiasma. a. At chiasma crossing over takes place(paternal and maternal segments exchange) 3. Metaphase: Pairs of homologous chromosomes line up 4. Anaphase: tetrads are broken and homologues go to opposite poles 5. Telophase: same as mitosis except with replicated chromosomes Lecture 13 and 14 notes 6. Cytokinesis: Cell splits and forms two cells with same amount of chromosomes as starting cell Meiosis 2: Same as mitosis How is genetic variation promoted? Crossing over Independent assortment: bivalents can line up in different ways in meiosis 1 and be put in different cells in meiosis 2 Fertilization: Out crossing from different people can make new combinations Zygote: Sperm + egg diploid cell Nondisjunction: When a set of homologs or both sister chromatids separate to the wrong pole Aneuploid Zygotes: Chromosomes with too few or too many chromosomes Trisomony: extra copy of chromosomes Monosomy: lack of chromosome Chapter 14: DNA Replication DNA Structure Made up of sugar phosphate backbone and nitrogen containing base One strand runs from 5 end( has exposed phosphate group) to 3 end ( exposed hydroxyl group) and the other strand is anti-parallel and run 3 to 5 forming a double helix Guanine and cytosine are stronger because they have 3 hydrogen bonds DNA Replication Replication bubbles form when DNA is replicating and replication forks are the y shaped regions o Eukaryotic have multiple bubbles Lecture 13 and 14 notes o Prokaryotic have single Leading strand(Strand with 5-3) goes one replicates that strand in one way in the bubble and lagging strand( strand with 3-5) replicates the other way in the bubble How is the helix opened and stabilized? Helicase: catalyzes the breaking down of hydrogen bonds between bases Single-strand DNA binding proteins(SSBPs): attach to the strands to prevent them from rebinding or closing Topoisomerase: cuts and rejoins DNA downstream of the fork o Relieves twisting forces How is leading strand synthesized? DNA polymerase(enzyme that catalyzes the making of DNA) requires a primer( few nucleotides of RNA added to template) Primase adds these RNA segments going toward the 3 end How is lagging strand synthesized? Short fragments are made called Okazaki fragments and DNA polymerase 1 removes parts to create gaps Okazaki fragments are put together by DNA ligase to form a continuous strand This is why lagging is called the discontinuous strand This multi enzyme machine is called Replisome Replicating the ends of linear chromosomes Made up of telomeres that are short repeating bases that don’t contain any genes In the leading strand telomeres are fine but in the lagging strand telomeres are shortened during DNA replication Caused by primer being removed at end of chromosome leaving a single strand DNA that degrades Lecture 13 and 14 notes How is it prevented? Telomerase adds more bases to the end of the lagging strand catalyzes the synthesis of DNA from a RNA template carried with it Chromosomes of somatic cells continually shorten How is DNA replication so accurate? DNA polymerase proofreads it’s work removing bases if it’s mismatched and correcting it by acting as a exonuclease and removing deoxy ribonucleotides How is DNA repaired? Nucleotide excision repair system recognizes theres an error and removes section of single stranded DNA and uses the other strand as a template to make new DNA
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