EXSC%223:%Week%of%9/12/16%%Notes%from%the%textbook%Ch.%3.10%3.10%The%cell%cycle%consists%of%interphase%and%a%mitotic%phase%• Cell%cycle:%changes%a%cell%goes%through%from%when%it%is%formed%to%when%it%reproduces%• Two%major%periods%for%the%cell%o Interphase:%cell%grows%and%carries%out%normal%activities%§ G1%(gap%1%subphase)%• Metabolically%active%• Synthesizing%proteins%• Growing%rapidly%• Most%variable%in%length,%can%last%minutes%to%years%• Cells%that%permanently%stop%dividing%are%in%the%G0%phase%§ S%phase%• DNA%is%replicated%to%ensure%the%two%future%cells%will%have%identical%copies%of%genetic%material%• New%histones%made%and%assembled%into%chromatin%§ G2%(gap%2%subphase)%• Enzymes%and%other%proteins%needed%for%division%are%synthesized%and%moved%to%their%proper%sites%• By%the%end,%centriole%replication%is%complete%o Nuclear%division%(mitosis):%nucleus%divides%into%two%nuclei%§ Prophase:%nuclear%envelope%dissolves,%chromatin%condenses%into%chromosomes%§ Metaphase:%chromosomes%line%up%at%metaphase%plate%§ Anaphase:%sister%chromatids%are%pulled%apart%§ Telophase:%cleavage%furrow%forms,%nuclear%envelope%reforms%§ CELL%division:%Cytokinesis%%Lecture%Notes%9/12%%Chromosomes%• They%come%in%pairs%in%humans%o diploid%o Two%copies%of%each%gene%(1%from%mom,%1%from%dad)%• Chromatin%vs%chromosomes%o Just%different%states%of%DNA%o Two%sides%of%the%same%coin%Chromatin%Chromosome%Uncondensed%Condensed%Not%visible%under%a%light%microscope%Visible%under%a%light%microscope%Loosely%wound%Tightly%wound%DNA%is%in%this%state%majority%of%the%time%DNA%is%only%in%this%state%during%mitosis%and%meiosis%• Centromere:%point%at%which%two%strands%of%DNA%attach%o It%is%marked%by%a%DNA%sequence%o Present%in%chromatin%and%chromosomes%• Sister%chromatids:%2%strands%of%DNA%connected%by%a%centromere%o In%mitosis,%microtubules%attach%to%kinetochores%which%are%attached%to%centromeres%o Sister%chromatids%are%separated%in%anaphase%• Telomere:%DNA%sequences%found%at%the%end%of%chromatin%o End%caps%o Don’t%code%for%any%genes%o DNA%polymerase%can’t%read%end%sequence%so%DNA%wouldget%shorter%and%shorter,%the%telomeres%prevent%this%degradation%o Telomerase:%enzyme%that%rebuilds%end%caps%o Present%on%both%ends%of%the%DNA%strand%Cell%cycle%• 2%phases%interphase%and%mitotic%phase%• cells%spend%most%of%their%time%in%interphase%• interphase%subphases%o G1:%growth%§ Checkpoint:%make%sure%everything%is%in%its%proper%place%to%advance%in%the%cell%cycle%o S:%DNA%replication%and%growth%o G2:%growth%and%final%prep%for%division%§ Enzymes%and%regulatory%proteins%for%the%mitotic%phase%are%produced%§ Checkpoint:%make%sure%cell%is%ready%for%division%o G0:%cell%stops%in%the%cell%cycle,%never%enters%S%phase%§ Sometimes%called%“post-mitotic”%or%“amitotic”%§ Most%cells%are%always%in%G0%• DNA%replication%in%S%phase%o Helicase%unwinds%the%DNA%and%separates%the%2%strands%o DNA%polymerase:%enzymes%that%work%together%to%read%the%template%and%bring%in%complementary%nucleotides%for%the%existing%strand%(template)%§ There%is%a%DNA%polymerase%on%both%strands%(leading%and%lagging%strands)%• Leading:%DNA%polymerase%works%continuously%• Lagging:%DNA%polymerase%makes%complementary%pieces%in%fragments%(Okizaki%fragments)%o Ligase%comes%and%connects%the%Okizaki%fragments%• Mitotic%Phase%o Mitosis:%a%subphase%of%the%mitotic%phase%§ MITOSIS%IS%THE%DIVISION%OF%THE%NUCLEUS%NOT%THE%CELL%o Cytokinesis=cell%division%§ Can%begin%before%mitosis%is%finished%o Early%vs%late%prophase%§ Early%prophase:%spindles%have%not%yet%moved%to%opposite%sides%of%the%cell%§ Early%prophase:%there%is%still%a%nucleus%• Late%prophase:%the%nuclear%envelope%dissolves%§ Chromosomes%condense%in%early%prophase%§ Late%prophase%• Nuclear%envelope%degenerates%• Spindles%are%on%opposite%sides%of%the%cell%• Microtubules%start%pushing%chromosomes%to%the%center%o Metaphase%§ Very%brief%§ All%chromosomes%lined%up%at%the%center%(metaphase%plate,%equator)%§ Chromosomes%are%still%attached%at%the%centromere%o Anaphase%§ Sister%chromatids%are%pulled%apart%§ Microtubule%structures%attach%to%kinetochore%proteins%o Telophase%§ Nuclear%envelope%reforms%§ Contractile%ring%at%the%cleavage%furrow%forms%§ Cells%start%to%separateàdivide%all%contents%equally%• Cell%cycle%regulated%by%cyclin%and%cdk%o Both%are%proteins%o Work%together%to%produce%MPF%(mitotic%producing%factors)%o Cdk%will%always%be%present%regardless%if%cell%will%go%through%mitosis%or%not%o Cyclins%vary:%sometimes%they%are%prevalent,%sometimes%not%o Regulate%progression%of%the%cell%by%regulating%the%amount%of%cyclin%present%§ Cyclin=cytosolic%protein%§ Produced%in%standard%protein%synthesis%§ Eliminated%by%ubiquitin%proteasome%pathway%%Notes%from%textbook%4.3%4.3%Connective%tissue%is%the%most%abundant%and%widely%distributed%tissue%in%the%body%• Common%characteristics%o Same%origin:%all%connective%tissue%comes%from%mesenchyme%o Degrees%of%vascularity:%some%avascular,%some%highly%vascularized%o Extracellular%matrix:%connective%tissue%largely%composed%of%non-living%extracellular%matrix%in%addition%to%cells%§ Allows%connective%tissue%to%bear%weight,%withstand%high%tension,%endure%abuses%and%abrasion%• Structural%elements%o Ground%substance%§ Unstructured%material%that%fills%space%in%between%cells%and%fibers%§ Composed%of%interstitial%fluid,%cell%adhesion%proteins,%and%proteoglycans%o Fibers%§ Proteins%that%provide%support%§ 3%main%types%• Collagen%• Elastic%• Reticular%o Cells%§ Exist%in%immature%(-blast)%and%mature%(-cyte)%forms%§ Primary%cell%types%for%different%types%of%connective%tissues%• Connective%tissue%proper:%fibroblast%• Cartilage:%chondroblast%• Bone:%osteoblast%• Blood:%hematopoietic%stem%cell%• Types%of%connective%tissue%o Connective%tissue%proper%§ Loose%connective%tissues%• Areolar%• Adipose%• Reticular%§ Dense%connective%tissue%• Dense%regular%• Dense%irregular%• Elastic%o Cartilage%§ Hyaline%cartilage%§ Elastic%cartilage%§ Fibrocartilage%o Bone%§ Osseous%o blood%%Lecture%notes%9/14%%4%types%of%tissue%1. Nervous%2. Muscle%3. Epithelial%4. Connective%• Epithelial%and%connective%are%the%most%likely%to%go%through%mitosis%• Epithelial%tissue:%most%likely%to%develop%cancer%Connective%tissue%• Found%everywhere%in%the%body%•
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