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ANSC 1000 Exam 2 Lecture 3-5

by: Brianna Notetaker

ANSC 1000 Exam 2 Lecture 3-5 ANSC 1000

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Brianna Notetaker

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These notes cover the genetics that have been discussed so far.
Introduction to Animal Sciences
Alese Grey Parks
Class Notes
animal, Science, ANSC
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This 29 page Class Notes was uploaded by Brianna Notetaker on Sunday September 25, 2016. The Class Notes belongs to ANSC 1000 at Auburn University taught by Alese Grey Parks in Fall 2016. Since its upload, it has received 4 views.


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Date Created: 09/25/16
ANSC 1000Exam 2 Lecture 3 Fat Deposition Development& Deposition  Adiposedevelopmentbeginsduringmid-to-latestagesoffetal development  At birthanimalshaveverylittlefat o Example:Pigs have~2% fat at birth o Bodytemperaturecontroliscriticalin piglets  As animalgrows,fat depositionoccursbyenlargementofindividual fat cells,andfor a shortperiodoftime newfat cells develop o Most offat developmentbyhypertrophy(increaseincell size) Deposition  Fat is depositedatspecificlocations,andasthe animalgrows,it developsfurtherfrom theselocations: o Kidney,pelvicandheart fat o Subcutaneousfat o Intermuscularfat o Intramuscularfat  Kidney,pelvic,andheart fat (KPH) – protectsthe organsfrom impacts andworks as insulation o Makes up 3.5% ofcarcass weight (USDA Choice) o Fat surroundskidneyevenin youngcalves o Increases as weight increases o Dairybreedshavehigherkidneyfat thanbeefbreeds even with less bodyfat o Geneticdifference  Subcutaneousfat(underskin)- insulation o Largest quantityoffat in the bodyofhogs o Is depositedinlayersandconnectivetissueseparatesthesefat layers o Composedofseveral layers o Subcutaneousfatiswaste when theyare slaughtered;hogsthat havesubcutaneousfatintheirstomachsis desirable,onthe loin is not  Intermuscularfat(called"seam fat"in the tradeindustry) o Located betweenthe muscles o Largest quantityoffat in cattle– mostof theirbodyfat is located in theintermuscularfat o Intermuscularfatoftensurroundsmovingmuscle parts;fills spaces betweenbone& pointsofmuscle attachment &often cushionsmusclesduringlocomotion o Large depositsofintermuscularfatoftencauses problemsfor the packer andretailerinthe merchandisingofcuts 
  Intramuscularfat(marbling) o Located betweenmuscle fibersand withinmusclefibers;flavor anddesirable o Calledmarbling--indicatorofpalatability  Remember:Maturity(age)and marblingare2 main factors incarcass qualitygrades  An animalthatisrelativelyimmaturewithgood muscling providesa goodqualitymeat o Most depositionisinthe laterstages ofgrowth 2 o First to leaveifanimalis starved o Marketingliveanimalsonfullfeed:  0.4 to 0.5inches B.F. = 60-70% Choice(dependingon breed)  Measuredbetweenthe 12th/13thribs 
 Maturity,Sex,andFat Deposition  Younganimalsgrowrapidlyandmore muscle proteinthanfatis depositedatthisearlystage o As the animalmatures,agreater portionofthe gain is fat  Sex of animalmakesa bigdifference inrate offat depositionasanimal matures: o Intact (noncastrated)malesare normallytheleanest  Cattle:steer normallyleanerthanheifer;Dairycows pull energyfrom fatwhen havinga calf  Hogs: gilts havemore muscle (less fat)thanbarrowsat market weight;don’tknow why Sex andCarcass Composition Sex andFat Deposition  Hormonesplaya majorrole infat deposition 3 o Testosteronestimulatesmuscledevelopmentandhasan inhibitoryinfluenceonfatdeposition;moretestosterone=more muscle andless overallbodyfat o Bullsandrams havemore efficientweight gains plusmore muscular,trimmer carcasses;bullsare castratedtoprevent them from expendingenergyfighting  Testosteronealsoinhibitsintramuscularfat;animalshave to be fed to heavierweights o Estrogensincreaserate ofclosure ofepiphysealplate(growth plate)anddepositsfatearlier  Heifers readyfor market ~150 lb.lighterthansteers Muscle Structure  Contractionismajorfunction o Basisfor locomotion,digestion,breathing,vision,circulationand more  Muscle tissuecontainsuniqueproteinsarrangedinfilamentsthat interactbyslidingpasteach otherto providecontractileforce o Organizedfilaments= Striatedtissue  Skeletal& cardiac o Filamentslackingorganization=Non-striatedtissue  Smooth  Muscles are madeup ofbundlesofmuscles  Muscle bundlesaremade upofindividualmusclecells 4 o Synonyms:myocyte, muscle fiber,myofiber  Myofibrilsarethe basicfunctionalunitofthemuscle fiber contractile system o Made upofmicrofilaments o Actin(thinmicrofilament) o Myosin(thickmicrofilament)  Meat is more tenderin youngeranimalsbecausethereis less connectivetissueandthe muscles havebeen usedless SkeletalMuscle Structure Muscle → muscle bundle → muscle cells / fibers → myofibrils → actin & myosin 5 MuscularSystem Development  Totalmuscle-cellnumbersare geneticallyestablishedbeforebirth  Postnataldevelopmentisanincrease insize o Muscle fibersgrow in diameterinlength o Tendernessdecreasesas the animalagesbecause ofconnective tissue  There becomesmore connectivetissueandmore cross- linkingofthe connectivetissue PostnatalDevelopment  Example:Swine  At 80 daysofage: o ~50% ofmuscle-fibergrowth achieved o Intramuscularfatstartsto increase o Water contentdecreases  At 120 daysofage: o Muscle-fibergrowth ~75% complete o Fat is increasingrapidly  At 150 daysofage: o 95% ofmaximumfiber diameteris attained o Readyfor market o Additionalweightgainis fat AnimalGrowthCurve*(must be ableto draw)  Sigmoidalor S-shaped o Holdsfor allspecies  Increase insize relativeto time 6  Complex!Bodypartsgrowat differentrates  Nutrition,genetics,environmentandherdhealthallinfluencerateof growth  Phases ofthegrowth curve o Relativelylittlegrowthbefore birthandinitialincreasefollowing birthis slow o Early --rapidgrowth ofthe essentialorgans,skin,andbone  Head andlegs are proportionallygreaterthanthetrunk o Furtherdevelopmentofthe organs,skin,andboneplusvery rapidmuscle growth.Some fat is startingtobe deposited  Bodybecomeslonger butstilllacks depth 
  Weight gainsare rapidandefficient,mostlydueto muscle andbonegrowth 
  Bonegrowth is nearlycompletebythe endofthe phase  Some fat is beingdeposited,evenduringthisperiodof leangrowth o Last phase-- increasein growth is nearlyallfat 7 GrowthandDevelopmentofBone, Muscle, andFat ConsideredSeparately 8 ANSC 1000Exam 2 Lecture 4 What is “Genetics?”  Genetics– thescience ofheredityandvariation  Heredity – sharingofgenes betweenindividualsandtheirancestors  Variation–differences amongindividuals  Genes– containedinthechromosomesofevery bodycell  Alleles– differentforms ofgenes on the same location(locus)on pairedchromosomes CellTypes andStructures 9 Chromosomes  Nucleuscontainsrod‐likechromosomes o “coloredbody”(with staining)  Constrictionwherepointofattachmentlies= centromere  Chromosomesarein pairs o Each containsgenes o Whencells divide,chromosomesdoas well Chromosomes–Species Variation(Needto knowchart) Pairs of Chromosomes in Livestock and Poultry Species Number ofPairs Turkeys 41 Chickens 39 Horses 32 Cattle 30 Goats 30 Sheep 27 Humans* 23 Swine 19 *Shown for comparison  Anatomically,swinearethe closestto humans DNA  ChromosomesconsistofDNA o Deoxyribonucleicacid o Two strandsofnucleotidesas“doublehelix”  Segments ofDNA are genes  Sequence ofDNA codes for particularprotein  Locationofgene on chromosome= locus  Contains: o Deoxyribosesugar o Phosphate o One of4 bases
  Thiscombinationiscalleda nucleotide
 10  Nucleotidestogetherform a strandthatishalfoftheDNA molecule DNA Bases  Adenine(A)pairswith Thymine(T) 
  Guanine(G)pairswith Cytosine(C)
  Duringcell division(mitosisandmeiosis),chromosomesreplicateby unwindingtheDNA strandsand forminga new strandalongside o Old strandserves as thetemplatefor creatinga newcopy  A on old,T on new;G onold,C on new  Forms 2 doublestrandedmoleculesfrom1 11 Whatis a Gene?  Basicunitofinheritance  Shortsection ofa chromosome,which is a longstrandofDNA o Segments ofDNA DNA Coding  Genescode for proteins
  Proteinsare made ofaminoacids(20) 
  Aminoacidsare coded byDNA tripletsequence o 3 nucleotides o Ex:TTC andTTT code for lysine
  Analogoustolettersofa word o TripletsequenceofDNA = letter o Aminoacids= lettersofa word o Protein= word 
 RNA  Ribonucleicacid  Three types o TransferRNA (tRNA)  IdentifiesaminoacidandbasetripletinmRNA strands o Messenger RNA (mRNA)  Carries“code” for a particularprotein o RibosomalRNA(rRNA) 12  Requiredfor ribosomalstructureandfunction ProteinSynthesis  Transcription = first step
 o SynthesisofRNA (mRNA andtRNA)from DNA in thenucleusby matchingthe sequencesofbases  Messenger RNA (mRNA) o Similarto DNA butis single‐stranded o Thymine(T)replacedbyUracil (U) o Tripletsequencefor one aminoacidin mRNA= codon o Transcribesencodedmessage andtravelsfrom nucleusto ribosome  Ribosome= siteof proteinsynthesis o RibosomecomposedofrRNA andprotein  tRNA is codedbyDNA in nucleus& moves outto cytoplasm o Identifiesanduniteswithoneaminoacid  Specificunion  ContainsanticodoncomplementarytomRNA  Ex:mRNA’s UUC attachesto tRNA’sAAG  mRNA attachestoribosomefor translationofmessage intoprotein o TripletcodonofmRNA associateswithanticodonoftRNA (specificaminoacid attached) o Begins at oneend ofmRNA andcontinuesalongthelength  Aminoacidsform peptidebonds o Fullyformed proteindissociatesfromribosome 13 Genesand Chromosomes  Chromosomesarein pairs o Containgenesfor the same traits o Homologouschromosomes  Diploidcells= cells thatcontainbothpairsofchromosomes o Non‐sexcells 14  The genes at each locuson onechromosomestrand“matches” (affects the same traitas)a gene at the correspondinglocusonthe homologouschromosome  The transmissionofgenes to offspringdependsentirelyonthe transmissionofthese chromosomestothe offspring 
 Sex Chromosomes  X & Y chromosomesexistas a pair inwhich one doesnotcorrespond entirelyto otherinterms of where the lociare present 
  The Y chromosomeis much shorterthantheX 
 15  Determinethe sex ofan animal  Female hasXX; Male hasXY o The femalecan contributeonlyXs tothe geneticmake-upof the offspring  The malecan contributeeitherX or Y o Male determinessexofthe offspring Sex Chromosomes– Birds  Female determinesthesex ofthe offspring  The chromosomesareidenticalinthe male(XX) butin thefemale are different(XY) Alleles  Genesthatoccupy correspondinglociin homologouschromosomes, butthataffect thesame character in differentways are calledalleles o Alternateformsofthe same gene o Ex:blackor red color  Genesthatare alike andthataffect the character developinginthe same wayare called identicalalleles 16 InheritanceofGenes  Everyindividualgets50% of itsgenes from each parent o Two allelesfor each gene, one per parent o “Paired”(homologous)chromosomescontaingenesforthe same traits  Maybe homozygousor heterozygousfora given trait o Homozygous= two identicalalleles o Heterozygous= two differentalleles  Dominanttraits“mask” the expressionoftherecessive o Dominant= capitalletters o Recessive= lower case letters GenotypeVs.Phenotype  Genotype= the geneticmakeupofan individual o Ex:BB vs.Bb  Phenotype= the physicalmanifestationofananimal’s genes o Ex:Blackvs. Red  Genotypicratio(prevalenceofa specificgenotypein a population) maydiffer from phenotypicratio o Ex:BB andBb = black, whilebb = red  Two genotypesresultin the samephenotype 17 Mitosis  Continuousprocess  Four stages o Prophase o Metaphase o Anaphase o Telophase  Motheranddaughtercells haveexactlythe same geneticcomponents 19 InterphaseandProphase Replication 20 Prophase  Chromosomesbecomecoiledandvisible
  Each chromosomeis seenas a pair ofsisterchromatids 
  The nucleolusdisappears
  Mitoticspindleforms
  The nuclearenvelopedisappearsattheend of prophase Metaphase  Centrosomesareat oppositepoles  Chromosomesbecomearrangedonthe metaphaseplate  Each sisterchromatidis attachedtoa kinetochoremicrotubule
 21 Anaphase  Duplicatedcentromeresofeach pairofsister chromatidsseparate 
  Now‐daughterchromosomesbeginmovingtoward oppositepolesof the cell 
  Bythe end ofanaphase,acompleteset ofchromosomeshas assembledateach poleofthe cell. Telophase  Chromosomesassembleatthetwo poles
  Chromosomesbegintouncoil
  Nuclear envelopereforms,the spindle
disappears,andthenucleolus reforms 
  Cytokinesis–divisionofthe cytoplasm
  Formationofa cleavage furrowasthe cell begins pinchingintotwo newcells 22 TelophaseandInterphase Meiosis  Interphase  MeiosisI o Homologouschromosomesdividedintotwohaploidcells  InterphaseII  MeiosisII o Similarto mitosis o Endresultis four haploidcells 23 CrossingOver – ProphaseII 24 Meiosis Gametogenesis  Productionofsex cells occurs inthe testicleor ovary o Gametesfrom the testicleare sperm (spermatogenesis) o Gametesfrom the ovaryare ova(or eggs – oogenesis)  Each newlyformedgamete containsonlyoneofeach original chromosomepair o Whengametes recombineto form zygotes,original# of chromosomesrestored(not2x normal) 25 
MeiosisandGametogenesis  Meiosisoccurs o In the primordialgermcells near theouterwall ofthe seminiferoustubulesofeachtesticle o Near the surface ofeach ovary  Chromosomesreplicatesothepair is doubled  Each paircomes together throughsynapsis  The cell is thencalled: o Primaryspermatocyte o Primaryoocyte  Steps initiallysimilarforbothmale& female Spermatogenesis  Process in males where each meiosisproduces4equallysizedsperm cells  Cellsfrom testes produceprimaryspermatocyte  Primaryandsecondaryspermatocytesundergodivision  Spermatid o Lose much cytoplasmanddevelopa tail o Matureintosperm byspermatogenesis 26 Oogenesis  The primary(like themale)containsa tetrad 
  The firstmaturationdivisionaftertheprimaryoocyte is formed producesa larger nutrientcontainingcell(secondaryoocyte)anda smallercell (first polarbody) o Each ofthese cellscontainsa dyad 
  The secondmaturationdivisionproducestheovum,andthe second polarbody o Each containstwochromosomes o The firstpolarbodymay alsodivide,butallpolarbodiesdieand are reabsorbed
  The ovum,like the sperm containsonlyhalfoftheoriginal chromosomepair(one chromosome)
 27 Fertilization  Whena sperm andovum unite,each contributesonechromosometo the resultingpairofchromosomes  Ovum is fertilizedandnowcalleda zygote o Fertilizationisthe unionofthe spermand ovumalongwith the establishmentofthe pairedconditionofthe chromosomes o The zygote is termeddiploid o Doubleor pairedchromosomes  Gametesare haploid o One single unpairedchromosome  Gametogenesisreducesthenumberof chromosomesina cell to half the diploidnumber o “Haplo”meanshalf 
  Fertilizationreestablishesthenormaldiploidnumber o “Diplo”meansdouble 28 29


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