This document discusses several key processes of evolution and how they act on different types of genes including DNA, rRNA, mRNA, and tRNA genes. It begins by describing the main types of genetic changes including base substitutions, indels, and inversions. It then discusses how natural selection influences these genetic changes, providing examples like DNA polymerase proofreading. The document goes on to discuss how genetic changes can impact specific gene regions like promoters, exons, introns, and more. Lastly, it discusses mechanisms for maintaining high copy numbers of ribosomal genes, which developed through evolutionary processes like endosymbiosis.
Properties and effects of transposable elementsDr. sreeremya S
The defining property of transposable elements is their mobility; i.e. they are genetic elements that can move from one position to another in the genome.Beyond the common property of mobility, transposable elements show considerable diversity. Some move by DNA intermediates, and others move by RNA intermediates
Properties and effects of transposable elementsDr. sreeremya S
The defining property of transposable elements is their mobility; i.e. they are genetic elements that can move from one position to another in the genome.Beyond the common property of mobility, transposable elements show considerable diversity. Some move by DNA intermediates, and others move by RNA intermediates
Transposable elements (TEs), also known as "jumping genes" or transposons, are sequences of DNA OR Mobile DNA elements that move (or jump) from one location in the genome to another. They are also known as jumping gene.
- Bạn là doanh Nghiệp sản xuất hoặc phân phối độc quyền trong lĩnh vực Bất Động Sản và Mỹ Phẩm.
- Bạn có ý tưởng nhưng chưa có kế hoạch vận hành và truyền thông cụ thể hoặc chưa có kinh nghiệm về quản lý doanh nghiệp.
- Bạn là Doanh Nghiệp Bất Động Sản hay môi giới Bất Động Sản, nhưng bạn đang lo lắng về nguồn khách tiềm năng phát sinh.
- Bạn muốn phát triển thương hiệu, đẩy nhanh doanh số bán hàng....nhưng chưa có định hướng cụ thể,
Công ty CP truyền thông DREAM PARADISE MEDIA - Đơn vị truyền thông – Marketing số 1 tại Việt Nam ra đời với sứ mệnh hiện thực hóa ước mơ và nâng tầm thương hiệu của các doanh nghiệp. Với những chuyên gia và đội ngũ nhân viên kinh nghiệm và sáng tạo, DREAM PARADISE MEDIA tự tin sẽ mang đến cho bạn những giải pháp và chiến lược Marketing – Truyền thông tối ưu nhất, vừa tầm với tiềm lực tài chính của bạn nhất.
Từ khi ra đời DREAM PARADISE MEDIA đã và đang được sự tín nhiệm của các đối tác với các dịch vụ:
• Xây dựng trọn gói Truyền Thông cho Startup – Tiết Kiệm chi phí
• Phát triển hệ thống phân phối cho doanh nghiệp
• Quảng cáo & lập kế hoạch truyền thông tất cả các kênh Digital Marketing
• Cung cấp khách hàng bất động sản tiềm năng theo dự án
Hãy liên lạc với chúng tôi qua hotline 0888129812 hoặc 0916200660 ( Mỹ )
Transposable elements (TEs), also known as "jumping genes" or transposons, are sequences of DNA OR Mobile DNA elements that move (or jump) from one location in the genome to another. They are also known as jumping gene.
- Bạn là doanh Nghiệp sản xuất hoặc phân phối độc quyền trong lĩnh vực Bất Động Sản và Mỹ Phẩm.
- Bạn có ý tưởng nhưng chưa có kế hoạch vận hành và truyền thông cụ thể hoặc chưa có kinh nghiệm về quản lý doanh nghiệp.
- Bạn là Doanh Nghiệp Bất Động Sản hay môi giới Bất Động Sản, nhưng bạn đang lo lắng về nguồn khách tiềm năng phát sinh.
- Bạn muốn phát triển thương hiệu, đẩy nhanh doanh số bán hàng....nhưng chưa có định hướng cụ thể,
Công ty CP truyền thông DREAM PARADISE MEDIA - Đơn vị truyền thông – Marketing số 1 tại Việt Nam ra đời với sứ mệnh hiện thực hóa ước mơ và nâng tầm thương hiệu của các doanh nghiệp. Với những chuyên gia và đội ngũ nhân viên kinh nghiệm và sáng tạo, DREAM PARADISE MEDIA tự tin sẽ mang đến cho bạn những giải pháp và chiến lược Marketing – Truyền thông tối ưu nhất, vừa tầm với tiềm lực tài chính của bạn nhất.
Từ khi ra đời DREAM PARADISE MEDIA đã và đang được sự tín nhiệm của các đối tác với các dịch vụ:
• Xây dựng trọn gói Truyền Thông cho Startup – Tiết Kiệm chi phí
• Phát triển hệ thống phân phối cho doanh nghiệp
• Quảng cáo & lập kế hoạch truyền thông tất cả các kênh Digital Marketing
• Cung cấp khách hàng bất động sản tiềm năng theo dự án
Hãy liên lạc với chúng tôi qua hotline 0888129812 hoặc 0916200660 ( Mỹ )
Avoid Shiny Object Syndrome in Digital MarketingTiffany Starnes
The digital marketplace is constantly changing and remaining relevant means staying ahead of the curve. But, in a cross-channel world with millions of options, how do pick the right ones? First, take a deep breath. Then, let’s talk goals. Set goals with clear metrics for marketing success. Couple that with a keen understanding of your audience and you will create relevant content that goes beyond platforms or channels to reach your core customer. Avoid being blinded by the bling of the coolest new platform and focus on reaching your ideal audience- where they are and with the information they want.
How to troubleshoot wireless connection problemsAlex Robert
Go ahead and reboot your PC, as well as your modem and router. To clear the modem and router caches, wait 60 seconds before you turn them back on again. Turning everything off and back on first ensures that it isn’t a temporary problem. It’s better to reboot now than to waste 30 minutes continuing on when you don’t need to.
Morsca International Limited is a professional fine & fashion jewelry manufacturer for 13 years. "Perfection" is a concept of our brand "Morsca".Each model is well designed by our excellent artist.Each design is unique. Morsca also applies the principle of ergonomics into design, aiming at producing the most comfortable and quality products for our clients. The new net type design avoids the uncomfortable feelings of traditional jewelry of skin scraping. The material we use is 100% complied with the international high standard which will never cause any unwell-symptom, such as allergy.
Our main products are silver 925 rings, earrings, pendants, bracelet bangle & necklace ect, which could be set with diamonds, gemstone, semi-gemstone, crystal glass & cubic zirconia ect.
Below is our company website: we also promote our styles on globalsources.
www.morsca.com
http://www.globalsources.com/morsca.co
Any inquiry you want to know about us, kindly contact us anytime through cutomerservice@morsca.com
w
Describe the role of different types of genomic changes in the evolut.pdfivylinvaydak64229
Describe the role of different types of genomic changes in the evolution of organisms. What are
the potential consequences of each of the following: chromosomal rearrangements; gene
duplications; insertion or deletions of transposons; mutations of homeotic genes or their
homeoboxes; polypoidy.
Solution
Genes are the hereditary units that pass the genetic information from one generation to the other
generation. Evolution is a process of development of new organisms as a result of genomic
modifications of the already existing species. The change in single nucleotide results in point
mutation, which is of different types such as silent mutations, missense mutations, nonsense
mutations, and frame shift mutations.
All mutations are not harmful. Mutations can either be good or neutral also. If the mutations
resulted in a new functional protein, which would be advantageous for the organism, they are
considered as good mutations. Mutation is the basic mechanism of evolution.
1). Chromosomal rearrangements or translocations involve the rearrangement of nonhomologous
chromosomal regions. This may result in viable or nonviable organisms.
For example, robertsonian translocation (ROB) is a type of chromosomal rearrangement (one
arm of chromosome goes to another chromosome and vice versa), which is observed in the five
chromosomal pairs of humans namely chromosome 13, 14, 15 21 and 22. These translocations
result in viable fetus.
2).
Gene duplication involved in the formation of autopolyploids and meiotic errors. Gene
duplication is often followed by divergent evolution. Eg: Duplication of single chromosomes
may cause autopolyploids. The three types of gene duplications are,
1). Duplication of entire genome
2). Duplication of single chromosome
3). Duplication of single chromosome of a group of genes
The proteins of globin superfamily are the example of proteins that exhibit gene divergence after
gene duplication.
3). Transposons are gene sequences (DNA, deoxyribonucleic acid) that can change their position
within the genome. Both prokaryotes and eukaryotes have transposons. In humans, about 45% of
genomes contain transposable elements.
A few mutagens induced into the coding exon region (Transposon insertion:) of gene thereby
insertion of new bases or deletion of the bases. Finally result in generation of truncated protein.
Transposon is a piece of DNA which gets inserted in to the DNA. All transposable elements
insert a staggered break in the DNA strand, means the strands become unequal, one become
large and another become small. The short DNA sequence can be found on both sides of a
transposable element, these are known as flanking direct repeats, and its sequence is
characteristic of each transposable element.
4).
Polyploidy is a state of having more than two paired homologous chromosomes. For example,
fusion of two diploid gametes of the plant or species in their 2n state result in tetraploids, we can
observe this in potato. Bananas and apples also pres.
1. MARK BOTIRIUS
P a g e 1 | 6
1 Two of the three key parts of evolution are: 1. Changes in the genetic material; 2.
Natural selection. Discuss how each of process acts on each of the following:
a. DNA (generally) b. rRNA genes c. mRNA genes d. tRNA genes
1a,1. General changesinDNA happenina varietyof ways. Overall,the mostcommontypes
of changesare base substitutions,indels,andinversions. (Rogers173). Base substitutionsare
furthercategorizedaseithertransitions(apurine orpyrimidine isexchangedforabase of the same
type) or transversions(apurine orpyrimidineisexchangedforone of the opposite type) with
transitionsbeingmore commonthantransversions. Base substitutionsare pointmutationsthat,
due to the redundantnature of the geneticcode,can eitherresultinasynonymousor
nonsynonymousmutation. Synonymousmutations,of course,willhave little ornoeffect(codon
biasnotwithstanding),while the effectof nonsynonymousmutationswill dependonthe properties
of the replacementaminoacidandcanrange fromno effecttoan extremelydeleteriousone.Next,
there are indels. Asitsname indicates,thisisachange in the DNA that resultsinthe additionor
deletionof geneticmaterial. The effectof these mutationscanvaryenormouslydependingonwhat
isbeinginsertedordeleted,andwhere itisinsertedordeleted. Forexample,if the indelisapoint
mutation,itoftencausesa frameshiftthatchangesthe readingframe of the gene thataltersthe
entire aminoacidsequence. Usuallythisproducesanonworkingprotein. Of course,indelsare not
limitedtosingle bases. Forexample,replicative transposons (Pierce 304) can insertlongstretchesof
DNA,oftendisruptinghostgenesinthe process. Also,Indelscanhave noeffectaswell. Much of
eukaryoticDNA isnon-coding. If the insertionordeletionoccursinan area of non-codingDNA that
doesnotalso have some otherfunction(suchasa promoter),oran area of an intronnotinvolvedin
some otheractivity(suchas splicing),thenthe indelcanhave noeffect. Indelscanalsocome froma
prophage leftbehindbyvirusesduringtheirlysogeniccycle thathassince mutated. (Rogers192-196)
I wouldbe negligentif Ididn’tpause here todiscusswhatcouldbe the most importantindel
of all,thatis alsolargelyunique tothiscourse. Thatis,the changesin DNA that isthe directresultof
endosymbioticevolutionarypathways. I wouldgive aspecificcitationhere,exceptthissource of
geneticvariationissoimportantandfundamental tothiscourse Iwouldhave tocite the firstnine
chaptersof Integrated MolecularEvolution. Examplesof thistype of indel are the presence of
mitochondrial andchromosomal genesinthe hostchromosome. These geneswere once apartof
the endosymbiontgenome thathave since moved(inserted) intothe hostchromosome andhave
beensubsequentlylost(deleted) fromthe original endosymbiont. Itshouldbe notedthatexamples
of thistype of indel are notlimitedtobacterial endosymbiontswithineukaryotes. A case in pointis
whena eukaryote hasanothereukaryote asanendosymbiont.
Lastly,there are inversions. Inthisgeneticchange,the DNA formsa loopduring
recombinationwhenone of the strandsbreaksintwoplaces. Whenthe strand isreintegrateditisin
a reverse orientationcausingthe sequence tobe subsequentlyinverted. The effectsfromthis
mutationcan be eitherminimal,apoptotic,orcarcinogenic. (Rogers173) (Iwasa478)
1a,2. Havingdiscussedthe effectsthatgeneticchangeshave onDNA (generally),Inow
turn myattentiontothe effectsof natural selectiononthese changes. Inotherwords,how does
natural selectioninfluence changesatthe level of DNA? One exampleisthe proofreadingfunction
of DNA polymerase. Thisisone instance where the firstchange inthe geneticmaterial discussed
(i.e.base substitutions) encountersanatural selectionprocess. There are manyDNA repair
pathwaysdesignedtocorrectbase substitutions. Forexample,DNA polymerasehasproofreading
capabilitiesduringreplicationanditscorrective capabilitiescanvarydependingonthe type of base
2. MARK BOTIRIUS
P a g e 2 | 6
substitution. Forinstance,if the base substitutionisdue todeamination,DNA polymeraseeasily
corrects the deaminationof cytosinetouracil butdoesnotcorrect the deaminationof 5-
methylcytosine tothymine. The reasonisbecause uracil doesnotbelonginDNA,while thymine
does.Base substitutionsof cytosine touracil are selectedagainst,whilebase substitutionsof 5-
methylcytosine tothymineare not. (Pierce 494) Likewise,transversionscause the DNA helixto
distortmore than translationsbecause purinesconsistof tworingsandpyrimidinesconsistof only
one ring. Asa result,base substitutionsthatare transversionsare alsoselectedagainst,sothat
transitionsare more common. Indelscanalsoexhibitselectioninthatsome typesare more
commonthan others. For example,genomewide repeatsalonecomprise over43% of the human
genome. (Watson206) Genome wide repeatsare causedalmostexclusivelybytransposons,
meaningthatintermsof differenttypesof indels,transposonsare highlyselectedfor. Now thatI
have coverednatural selectionasitaffectsgeneral DNA changes,Ican addressthe more specific
questionof what itmeanswithrespecttoa particulargene,namelyrRNA,mRNA,andtRNA genes.
1b, c, d; 1. All geneshave afewbasicand fundamental partsincommonthatrelate tothe
structure and functionof the moleculestheyproduce. These partsare the promoter,5’UTR (or the
firstexon),exons(e.g.euchromatin),introns(e.g.heterochromatinineukaryotes),3’UTR (the last
exon),andfinallyaterminationsite. All of the geneticchangesIhave discussedsofarhave the
abilitytooccur inany of these fundamental genesegmentsandresultinarange consistingof no
effecttoa deleteriouseffectforreasonsIhave alreadydescribed. Therefore,itismuchmore
efficienttosimplystate whatcanhappenwhenthese regionsare mutated,sinceIhave already
coveredthe typesof mutationsthatcan occur, and thenapplythatto rRNA mRNA,andtRNA genes.
The promoteris the locationonthe gene where transcriptionisinitiated. Changestothe
geneticmaterial of the promotercanresultinthe gene beingupregulated,downregulated,or
silencedaltogether. Thiswouldcorrespondinglyresultinapositive selection(if the genesare up
regulated) toanegative selection(ifthe genesare downregulatedorsilenced).If these genesare
the onescurrentlybeingexamined,the resultsare acorrespondingchange inthe expressionof
rRNA,mRNA,or tRNA genes. Nextisthe 5’ UTR.1
Thisregioncodesforthe 5’ UTR regionof mRNA,
whichiswhere the 5’ cap is added. Thiscap is importantbecause itiswhere capbinding proteins
attach. CBP’sare neededforproperattachmentof the mRNA tothe ribosome. A deleterious
mutationinthispart of the gene couldresultinimproperbindingof mRNA tothe ribosome and
therefore negative selection. (Rogers163) Followingthe 5’UTR regionon the listare the exons. This
isthe regionwhere the aminoacidsare coded. Geneticchangeshere affectthe proteinsthatthe
gene produces. The range of outcomesproceedsfromnone (i.e.asynonymousor othertype of
silentmutation) tobeneficial,(e.g.anaminoacidchange thatproducesa beneficialprotein) tolethal
(e.g.a frameshiftmutationthateliminatesacriticallyneededprotein). The resultingselection
possibilitiescorrespondinglyrange fromstronglyselectedfortostronglyselectedagainst.
Usually,exonsrefertogenesthatcode forproteins. Withregardsto rRNA,andtRNA
however,the codingregionsanalogoustoexonsare the SSU,LSU, 5s, 5.8s, ITS1, andITS2.
Mutationsinthese genescanhave a have a varietyof effects. The functionof the SSU,forexample,
isto transport the mRNA transcriptto the LSU, where itassociateswiththe LSUand properly
positionsthe transcriptinthe ribosome duplex fortranslation. If thisgene hasadeleterious
1In DNA, this is not always stated as a separateregion likeitis for mRNA, however it is always located within
the firstexon downstream from the promoter (in eukaryotes). In other words, the DNA code for the 5’ UTR of
mRNA is located in the firstexon. Likewise, the 3’ UTR is located in the lastexon.
3. MARK BOTIRIUS
P a g e 3 | 6
mutation,thenitispossible thatthe SSUwill notbe able to transportthe mRNA,orwill notbe able
to properlyinteractwiththe LSU resultinginaninabilitytotranslate mRNA toproteins.
The large subunitiswhere the enzymaticfunctionislocated. Itactuallycatalyzesthe reactionthat
joinsthe aminoacidto the growingpeptide chain. Mutationsinthisgene couldresultinalossof
enzymaticfunction,aninabilitytoproperlyassociate withthe SSU,oran inabilitytoproperly
associate withthe mRNA and/orthe growingpeptide chain. All of thiscouldleadtoalossof
translationof the mRNA. Furthermore,mutationsineitherthe SSUor LSU genescoulddistortthe
molecules,makingitimpossible toexitthe nuclearporestotravel tothe cytoplasm, where they
needtobe.
The functionof the tRNA’sisto bringthe amino acidsto the ribosome andtheyalsosetthe
geneticcode. Mutationsinthese geneswill likewise affectthese functions. Changesinthe
anticodonregionof the tRNA couldtherefore change the aminoacidcode forthat tRNA or cause it
to lose the ability tobindtothe tRNA altogether. Inaddition,the tRNA itselfmaylose the abilityto
interactproperlywiththe ribosome. All of these possibilitieswouldresultinanegative selection,
whichiswhythese genesare sostronglyconserved
Nextonmy listare introns. Surprisingly,intronscanbe foundinall three typesof RNA
genes. Changesinthese genescanaffecthow the intronsare splicedorevenif theyare splicedat
all. Withregards to mRNA,thiscould,of course,cause a failure toproduce a neededproteinor
produce a mutatedprotein. Inthe case of rRNAsand tRNAs,thiswouldcause a distortioninthe
shape of the moleculeswhichwouldcertainlyresultinanon-functional molecule.
Lastly,a mutationinthe 3’ UTR regionof the gene that codesfor mRNA couldaffectthe 3’ tail that is
addedat the endof the molecule. The 3’polyA tail functionstoprotectthe mRNA from
degradation. Withoutthistail,the lifeof the mRNA isgreatlyreduced,therebydestroyingits
functionality.
Finally,itwouldbe irresponsible if Ididn’tmentionone lastfacetof selectionongenesin
general,andrRNA,mRNA,andtRNA genesinparticular. Fromthe standpointof evolution,itis
probablyone of the most importantandagain,unique tothiscourse. It isthe selectionthatoccurs
followinganendosymbioticevent. Afteranendosymbioticevent,thereexiststwosetsof genesfor
Figure 1. This is anillustration from a power point presentationfrom Dr. Rogers class depicting the
rRNA, and to a lesser extent, tRNA genes.
4. MARK BOTIRIUS
P a g e 4 | 6
manycellularprocesses. Modernanalysisshows,however,thatthe genesthatfinallywindupinthe
hostchromosome are a mixture of hostandsymbiontgenes. Therefore,althoughitcouldbe due to
purelyrandomevents,itisalsolikelythatthe genesthatultimatelywoundupinthe chromosome
were the resultof selection. Those rRNA,mRNA,andtRNA genesthatbestservedthe organism
were positivelyselected.
2. Ribosomal genes are needed in multiple copies. Explain why. Outline some of the
mechanisms for creating or maintaining copy numbers sufficient for cells and organelles.
Explain how these processes might have developed and been selected for during
evolutionary processes.
The reasonwhy ribosomal genesare neededinmultiple copiescanbe demonstratedwitha
simple mathematical argument. There are an estimated106
proteinsinprokaryotesand109
for each
eukaryote (Rogers76) and the ribosome hasa clockspeedof only20 aminoacidsper second.
(Watson521) Therefore,inordertoproduce the needednumberof proteins,prokaryoteshave
approximately20,000 ribosomes,andeukaryotescontainapproximatelytenmillionormore.The
speedatwhichRNA polymerase cansynthesizearibosome isbetween50to 150 nucleotidesper
second. (Rogers76) UtilizingDr.Rogers’figure of 100 nucleotidespersecondgivesusatotal of one
day andthree hoursfor a single gene toproduce enoughribosomesforaprokaryote,andmore than
30 yearsfor a eukaryote. (Rogers76-77) Clearly,one gene isnotsufficient. Infact,the gene copy
numberpercell istypicallyinthe hundreds.
So howdo cellscreate enoughribosomal genes? Several methodshave beendiscussedin
class. The twoI findthe most interestingare the methodusedbythe protozoan Tetrahymena and
the frog Xenopuslaevis. Oneitherside of the Tetrahymena ribosomal gene are specialsequences
(calledA’andM repeats) thatare recognizedbyan endonuclease. A sectionof DNA containingthe
ribosomal gene iscutout,and telomeresare addedtoall of the endsexceptthe upstreamendof
the excerpt. Thisendcircularizesanda replicationbubble formsthattravelstowardsthe ribosomal
gene. The replicationbubble travelsall the waytothe openendof the excerpt,replicatingthe
ribosomal gene inthe process,andcreatinga DNA segmentthatissymmetrical aboutitscenter.
Figure 2. An illustration from Dr. Rogers’
PowerPoint. The top picture shows howone
end of the excerpt circularizes. The other end is
protectedfrom degradation bya telomere. The
replicationbubble travelsdownstream,
replicating the ribosomal gene inthe process.
The endresult is a DNA segment that contains
two copies ofthe ribosomal gene and is
symmetrical about its center.
5. MARK BOTIRIUS
P a g e 5 | 6
The new,linearDNA segmentcontainsA’-Msitesanditundergoesfurtherroundsof replicationto
produce the neededcopiesof ribosomal genes.
The mechanismforthe frog Xenopuslaevis issimilar. Like Tetrahymena,cutsare made at
signal sequencesflankingthe ribosomal gene. Inthe case of Xenopuslaevis,however,the cutsare
made at one or more ribosomal gene repeatsproducingseveral excerpts. These excerpts
individuallycircularizeandthenundergorollingcircle replicationtoincrease theirnumberto
produce the neededgene copy number.
The reasonI findthese two
mechanismsinterestingisthatthe
specificityof the splicingenzymesmakes
themverysimilartorestriction
endonucleasesfoundinbacteria. In
addition,rollingcircle replicationisalso
foundinbacterial conjugation. This
stronglysuggeststome that these
mechanismsmayhave beenobtainedby
these twoeukaryotesfromtheirbacterial
endosymbiontsinthe course of their
evolution.Thisanswersthe questionof
how these processesmighthave
developedinthe course of the evolution
of these twoparticularorganisms. These
bacterial mechanismswereconduciveto
creatingneededcopiesof ribosomal
genesandwere therefore subjectedtopositiveselectionandretained.
Anothermechanismforincreasingribosomalgene copynumberisprovidedbyamphibian
oocytes. The amphibianoogoniumdividesasymmetrically,withvirtuallyall of the mRNAsand
ribosomesgoingtothe largeroocyte. Thiseffectivelydoublesthe ribosomal numberforthe primary
oocyte therebyproviding the needednumberof ribosomes. One waythismechanismcouldhave
evolvedisbyselective pressuresatthe organismal level. Initially,the divisionof the oogoniumwas
symmetrical,producingzygotesof equivalentfitnessandribosomal numbers. Eventually,some of
the oogoniumproduceddaughteroocyteswithslightlydifferentproportionsof the parental
ribosomes. Those oocytesthatcontainedaslightlylargerproportionof ribosomeswere alittlemore
fit,and sowere positivelyselectedtoaslightdegree. Eventually,timeandnatural selectionresulted
inthe mechanismthatproducedthe fittestzygote,andthatmechanismwasone where the
oogoniumdividesasymmetrically.
Lastly,one of the mostcommonmechanismstoproduce the neededribosomal numberis
presentinplantsall aroundus. Many plantsare polyploidthroughaprocesscalledendomitosis,
where the genome iscopiedwithoutcytokinesis. Inotherwords,insteadof increasingonlythe
ribosomal genes,the entire genome isduplicatedleading toa veryhighC value andtherefore avery
highnumberof ribosomal genesaswell. (Rogers121) How could have polyploidyevolvedinplants?
Personally,Isee afewintriguingcluesinthe characteristicsof the life cyclesof manyplants. In
animals(like humans) ourmulticellularstage isdiplontic. Thatis,whenwe existasa multicellular
organism,ourgenome isdiploid. Plants,onthe otherhand,are not limitedtothisdiploidy. During
Figure 3. Another Dr. Rogers’ PowerPoint slide s howing the
rolling circle replicationmechanism usedby Xenopus laevis
increase ribosomal gene copynumber.
6. MARK BOTIRIUS
P a g e 6 | 6
part of theirmulticellularlife cycle,theyare diploid,likeus. Duringa differentpartof their
multicellularlife cycle,theyare haploid.ThisflexibilityinploidyIthinkiswhateventuallyledtotheir
abilitytobe polypoid,anditalsoexplainswhyanimals,suchashumans,donottolerate polyploidy
(itislethal tous). I thinka possible evolutionaryroute topolyploidyisthatsome ancientplant
ancestorwhose life cycle involved“alternationof generations”failedtoreduce itschromosome
number(N) duringmeiosis. Thisispossiblebecausewe know thatpolyploidyisnormallydue toa
failedreductiondivisioninmeiosis. (Futuyma505) Thisincrease inploidyledtoanincrease in
beneficial andneededgenes,suchasribosomal genes,whichledtoanincrease infitnessand
positive selection.
Works Cited
Futuyma,DouglasJ. Evolution.3rd. Sunderland:SinauerAssociates,2013.Hardback.
Iwasa,J and Marshall,W. Karp'sCell and Molecular Biology.8th. Hoboken:Wiley,2016.Book.
Pierce,BenjaminA. Genetics,A ConceptualApproach.New York:W.H.FreemanandCompany,2012.
Rogers,Scott Orland. Integrated MolecularEvolution.2nd.BocaRaton: CRC Press,2017. Hardback.
Watson,et al. MolecularBiology of the Gene. 7th. Boston:Pearson,2014.