Babs1201 Study Notes At Unsw

Transcript

BABS1201 Study Notes Life Universe = 13.8bya Solar System = 4.6bya Life = 3.8bya 1.8million species identied, thosands more each year, !ith 1"# 1"" million species in total, $ of !hich are arthopods %haracteristics of Life& 'eprodce (ro! and )evelop *etabolise 'espond 'espond to Stimli+nvironmental %han-es ave %ells /or-ani0ational nits 2ossess 2ossess the %hemicals of Life %arbohydrates o most most ab abndan ndant, t, chem chemic ical ally ly sim imp ple oror-anic anic molecles store+transport ener-y /mostly in plants, animals se lipids, strctral components monosaccharides lin to form oli-osaccharides /# 6 or polysaccharides 2roteins o )epe )epend nden entt on amin amino o acid acid se5 se5en ence ce,, lin lined ed by peptide bonds 4 dierent levels of or-anisation /shape# dependent Lipids o fats, oils, !a7es, cholesterol, fat#solble vitamins /, /, ), , 9, 9, mono mono-l -ly yceri ceride des s, didi-lyce lycerrides ides,, phospholipids ener ener-y -y stor storaa-e, e, str strct ctr ral al comp compon onen entt of cell cell membrane :cleic cids o formed by linin- ncleotides store+transfer store+transfer -enetic information ):, ': 2rions /proteinaceos infectios particles are altered proteins that can chan-e other proteins thro-h conformation. )omains )omains /classic /classication ation, , dened dened by %arl ;oese /compar /compared ed ribosomal ':, formed phylo-enetic tree& arya /3< sbdivisions # plantae, fn-i, animalia, <"# 1"" protist in-doms acteria /1> sbdivisions rcha rchaea ea /16 sbdi sbdivis vision ions s # many many are are e7tr e7tremo emophi philes les /halophiles, thermophiles, methano-ens # s!amps+marshes, s!amps+marshes, anaerobic and prodce methane • • • • • •           • • • 2a-e 1 ?liver o-danovsi 2roa 2roaryote ryotes s = bacteria bacteria @ archaeaA archaeaA thrive almost almost any!here any!here,, more in handfl of soil than the nmber of people !ho have ever lived Bacteria/Archaea Eukarya no#memb no#membran rane e aron arond d or-an or-anell elles es membra membrane# ne#enc enclos losed ed or-an or-anell elles es ncles /sally lar-est no ncles or-anelle simple, small /1BmA ".<#>N of livin- thin-s are made %?:, !ith 2OS also abndant, !hich Ioin to form macromolecles& a lar-e molecle formed by the 2a-e < ?liver o-danovsi  Ioinin- of smaller molecles sally by a dehydration reaction. *acromolecles /e7cept for some lipids are polymers of similar or identical sbnits /sally monomers lined by covalent bonds. 2olymer breado!n is hydrolysis as a !ater molecle is added to brea the covalent bond. 2a-e 6 ?liver o-danovsi )acromole cule Subunit Bond E%am&les Stora-e and Strctre Carbohydr ate *onosaccharid es /-lcose, can form disaccharides lie maltose Li&id Eatty cids /Pn G(, three fatty acids each Ioin to a -lycerol by an ester bond, varyin- in len-th, and nmber and positions of  doble bonds (lycosidic ond ster ond Starch /-lcose # stored by plants as -ranles /accessed by hydrolysis (lycogen /branched -lcose # stored by animals in liver and mscle cells /canFt sstain animal for lon- period of time Cellulose /Hippin- -lcose # strctre, component of plant cell !alls Chitin /-lcose !ith nitro-en -rops # e7oseletons in arthropods /insects, spiders, crstaceans ydrophobic /non#polar Satrated # no doble bonds in fatty acids bet!een carbons Unsatrated # 1@ doble bonds in hydrocarbon chain of the fatty acid, casin- ins 2hospholipids are t!o hydrophobic fatty acid tails connected to -lycerol, !hich is connected to a phosphate -rop !hich in trn is connected to a polar -rop lie choline /replacin- one of the fatty acids Energy Storage and !rans&ort # triacyl-lycerols or G(s Structure # phospholipids, sterols Chemical )essengers # steroids /cholesterol, -lycolipids -hotorece&tors # carotenoids Co"erings # !a7es 2a-e K o-danovsi ?liver ll amino acids consist of& central / carbon atom amino -rop /: 3@ carbo7yl -rop /%?? # hydro-en atom / a variable side#chain /' # determines !hether they are non# polar, polar or electrically char-ed /also hydrophilic • • • • • -rotein mino cids /" dierent ones that form polypeptides !hich fold into 3) strctre 2eptide onds Nucleic :cleotides 2hosphodies 2a-e 8 o-danovsi ;hen polymerised they become a bacbone !ith varios side# chains that determine ho! it folds and 3) strctre /primary, secondary, tertiary and 5aternary levels of foldin- determine nal shape Used as strctre /eratin, stora-e /casein, transport /haemo-lobin, hormones /inslin, movement /actin, en0ymes /scrase n0ymes # catalytic proteins selectively speed p chemical reactions !ithot bein- consmed, allo!in- reactions to be fast eno-h for a cell to srvive  /en0yme @ S /sbstrate Q S Q  @ 2 /prodct %atalysis occrs at the active site n0ymes lo!er the activation ener-y /  of  a thermodynamically favorable reaction, bt do not aect the e5ilibrim or free ener-y chan-e /R( # the difference in the ener-y bet!een the reactants and prodcts and cannot mae a thermodynamically nfavorable reaction favorable ): or ':, store hereditary information, polymers also called ?liver ll amino acids consist of& central / carbon atom amino -rop /: 3@ carbo7yl -rop /%?? # hydro-en atom / a variable side#chain /' # determines !hether they are non# polar, polar or electrically char-ed /also hydrophilic • • • • • -rotein mino cids /" dierent ones that form polypeptides !hich fold into 3) strctre 2eptide onds Nucleic :cleotides 2hosphodies ;hen polymerised they become a bacbone !ith varios side# chains that determine ho! it folds and 3) strctre /primary, secondary, tertiary and 5aternary levels of foldin- determine nal shape Used as strctre /eratin, stora-e /casein, transport /haemo-lobin, hormones /inslin, movement /actin, en0ymes /scrase n0ymes # catalytic proteins selectively speed p chemical reactions !ithot bein- consmed, allo!in- reactions to be fast eno-h for a cell to srvive  /en0yme @ S /sbstrate Q S Q  @ 2 /prodct %atalysis occrs at the active site n0ymes lo!er the activation ener-y /  of  a thermodynamically favorable reaction, bt do not aect the e5ilibrim or free ener-y chan-e /R( # the difference in the ener-y bet!een the reactants and prodcts and cannot mae a thermodynamically nfavorable reaction favorable ): or ':, store hereditary information, polymers also called 2a-e 8 o-danovsi Acids 2a-e > o-danovsi ?liver ter onds polyncleotides ?liver Acids ter onds 2a-e > o-danovsi polyncleotides ?liver Cell +ntegrity  Ghe membrane prevents n!anted ntrients and to7ins from enterin-+leavin-, and hence maintains cell inte-rity. Ghere !ere t!o proposed models for the membrane& )avson#)anielli *odel /1>3< # phospholipid bilayer !ith proteins above and belo! Elid *osaic *odel /1>K by Sin-er and :icholson # inte-ral membrane proteins sat inside, peripheral proteins above and belo!, !ith a cytoseleton spportin- itA had sidedness or asymmetrical distribtion of proteins, carbohydrates and lipids /lie cholesterol bet!een each side as many !ere formed inside the cell bt cannot pass to the otside the Hidity refers to the rapid movement of lipids o and proteins laterally # sho!n by& the fsin- of mose and hman cells, and proteins !ere mi7ed, not one#side hman, the other mose microscopy !ith staininE'2 /Horescence recovery after photo# bleachin- # alterin- ): to prodce proteins that lose color after laser beam e7posre to one section of the membrane, and over time color comes bac as this • •    Cell +ntegrity  Ghe membrane prevents n!anted ntrients and to7ins from enterin-+leavin-, and hence maintains cell inte-rity. Ghere !ere t!o proposed models for the membrane& )avson#)anielli *odel /1>3< # phospholipid bilayer !ith proteins above and belo! Elid *osaic *odel /1>K by Sin-er and :icholson # inte-ral membrane proteins sat inside, peripheral proteins above and belo!, !ith a cytoseleton spportin- itA had sidedness or asymmetrical distribtion of proteins, carbohydrates and lipids /lie cholesterol bet!een each side as many !ere formed inside the cell bt cannot pass to the otside the Hidity refers to the rapid movement of lipids o and proteins laterally # sho!n by& the fsin- of mose and hman cells, and proteins !ere mi7ed, not one#side hman, the other mose microscopy !ith staininE'2 /Horescence recovery after photo# bleachin- # alterin- ): to prodce proteins that lose color after laser beam e7posre to one section of the membrane, and over time color comes bac as this area is lled !ith non#0apped proteins *embrane members&   Li&ids  # of !hich "#61 is the theory that the proton -radient created by the respiratory chain /as it pmps protons ot of the mitochondria provides a means of  free ener-y /a proton motive force that can drive the activity of G2 synthase to -enerate G2 /o7idative phosphorylation. Ghis can be sho!n e7perimentally as mitochondria at p 8 that are shifted to p 4 have a brst of G2 synthesis !ithot any respiratory chain activity /no ?  is sed, so it is the protons that matter. Pf the inner membrane is made permeable to protons, no G2 is synthesised as no -radient is prodced. G2 synthase incldes inte-ral membrane proteins /located in mitrochondrial and chloroplast membranes in earyotes, or the plasma membrane in bacteria. G2 synthase has membrane#spannindomains that form a rotor !hich is driven by the movement of protons do!n the  @  concentration -radient /thin of it as electric char-es in a )% motor. 'otatin- the motor shaft in head pieceT cases conformational chan-es in the active sites that bind )2 and 2 i, and provides ener-y for this synthesis.  Ghe mitochondrial membrane is important for G2 synthesis as it is& Hid # allo!s  atoms+electrons+protein components to move and interact asymmetric # monodirectional proton pmps drive G2 synthesis thro-h -radients impermeable to ions # maintains proton -radient Pn total 3"#3 G2 e5ivalents /:) V .<G2, E) V 1.<G2 are prodced from one -lcose, !hich !old only prodce the initial :) and G2 in anaerobic fermentation. • • • /becomes part of 6 2a-e 1> ?liver o-danovsi 'espiration is controlled by allosteric en0ymes. Eor e7ample, phosphofrctoinae /2E9 catalyses the third step in -lycolysis, ho!ever it is inhibited by citrate /from the citric cycle and G2, !hilst bein- stimlated by *2. mino acids from proteins are broen do!n to acetyl#%o or intermediates !ithin the -lycolysis or G% cycle, !hilst carbohydrates and fats are both broen do!n aerobically into acetyl#%o /allo!s for recyclin- of some materials, !hich is !hat occrs !hen eatin- food. Ultimately it !ill form %?   and ? /the prodcts of respiration. Pn cases of lo! ?  spply, sch as intense e7ercise in seletal mscle cells and red blood cells, carbohydrate catabolism involves fermentation, and the -lcose is converted to lactate /lactic acid, !hich cases cell death if o7y-en spply is interrpted. ,rom (ene to ,unction  Ghe -enetic lan-a-e mst be accrately copied and passed on and readily accessed for the information contained. 2roteins had -reater comple7ity and " bildin- blocs, !hilst ): had a re-lar strctre and only 4 bildin- blocs so it !as believed proteins !old the means of inheritance, ho!ever lie binary the simpler lan-a-e still allo!ed for comple7ity. 7perimental data in the 1>4"s#early <"s s--ested that ): may be -enetic material. Eor e7ample, in 1><3 ershey and %hase -re! t!o batches of  bacteriopha-e G /virs that infects bacteria, one !ith radioactive slfr /present in t!o amino acids !hich labelled proteins, the other !ith radioactive phosphors !hich labelled ):. *i7in- these !ith bacteria infected the bacteria !ith the -enetic material of the virs, and pon centrif-in- to separate the bacteria from the virses they fond it !as the ): inserted into the bacteria. Pn 1><3 ;atson and %ric pblished the strctre of ): sin- moleclar models from X#ray diraction patterns, provin- it !as a doble heli7 /they ne! it had the ncleotide bases adenine, thymine, cytosine and -anine !hich stood on s-ars, each lined by a phosphate -rop after an  ? has been taen ot. ): is deo7yriboncleic acid, !hilst ': is riboncleic as it has an e7tra ?. %ombined !ith a phosphate -rop and base, it becomes a ncleotide.  O ( are doble#rin-s /&urines, so an  O ( !old prodce a strand to !ide /to be consistent !ith X#ray data. G O % are sin-le#rin-ed /&yrimadines  # smaller 2a-e " ?liver o-danovsi si0e compensated for by lon-er name, and !old prodce a strand too close for ):. ence one pyramidine had to be paired !ith one prine. Pn addition,  O G have t!o hydro-en bonds, !hilst % O ( have three, so they can only match lie G and %(. Pt forms an alpha heli7 /follo!s ri-ht#hand -rip rle, and bein- a heli7 /not spiral the strands are not evenly distribted bt close then far then close then far, !hich prodces almost a spiral shape !ith the resltin- ribbon /bt as the t!o strands are separate it is not a spiral. ach strand is considered antiparallel /rnnin- in opposite directions # the phosphateFs char-es face opposite directions and the carbons sit on the opposite sides. Ghe   base pairs /m lon-, "."1mm !ide, and this is comple7ed !ith histones /proteins to form ncleosomes, solenoids and eventally chromatin. istones maintain strctre of  the chromosome and help re-late -ene e7pression+activity. Pt is folded, coiled and condensed in preparation for cell division. *itochondria also have their o!n circlar ): !ithin their matri7 /the part inside the folds /cristae, not the tisse itself, !hich codes for proteins essential for normal mitochondrial fnction. NA 'e&lication Eirst, at the origin of re&lication helicase n!inds the strands and forms a small bbble. *ltiple ori-ins are needed to ensre replication occrs as 5icly as possible /in hman cells there are 6 billion base pairs all copied !ithin a fe! hors. ): polymerase then catalyses the addition of ne! ncleotides in opposite directions on each strand /as the t!o strands are anti# parallel. Pncomin- ncleotides have 3 phosphate -rops, and 2s are released to provide ener-y for the reaction /as those are hi-h# ener-y bonds. ): polymerase mst have a 3F ? -rop to add on to, and hence !ill move alon- the template strand from 3F>.>N of the -enome is the same in all people. (enes are not evenly distribted amon-st chromosomes /chromosome 1 has >68, ] has 31. Ghe fnction of  many -enes is still nno!n. Cell i"ision and 'e&roduction Pn proaryotes, cell reprodction occrs by binary ssion, in !hich ): replication commences at the ori-in of replication ntil each chromosome has been completely replicated, and each ori-in becomes separately attached to the plasma membrane. ?nce replication is complete, the plasma membrane -ro!s in!ards to prodce t!o da-hter cells and a cell !all is deposited. Pn hmans there are 1 billion cells+-ram of tisse, all derived from a fertilised e--, so this cycle mst be re-lated precisely. *ost cells replicate bet!een 1"#3" hors /!hilst . coli is "mins. %ell replication has t!o maIor phases /basically n4n /t!o of each individal sin-le chromosomen&   +nter&hase # -ro!th and replication of celllar components, -athers materials and ensres eno-h for replication (1 # -ro!th o S # ): synthesised /replicated+dplicated o (2 # cell components replicated /incldino centrosomes, !hich have perpendiclar centrioles # smaller component )itotic -hase # ncles divides and chromosomes are distribted to da-hter cells /mitsosis and the cytoplasm divides into t!o da-hter cells /cytoinesis o   )itosis # chromosomes condense,   -ro&hase centrosomes separate and form mitotic spindle   -rometa&hase # nclear membrane breas do!n, frther condensin-, centrosomes move to spindle poles !here they anchor, microtbles connect to centromeres /centre of dplicated ): by bindin- to inetochores /also made of microtble   )eta&hase # each chromosome attaches to a spindle pole /e5al pressre each !ay # if  not properly attached one cell !ill have an • •    2a-e < ?liver o-danovsi e7tra copy, the other missin- oneA :?G trisomy, as this isnFt meiosis   Ana&hase # protease che!s thro-h protein holdin- sister chromatids to-ether and they are plled apart casin- cell elon-ation   !elo&hase # nclear membrane reforms and chromosomes decondense o   Cytokinesis # cleava-e frro! /contractin- rin- of  microlaments in animals, cell plate made of  vesicles in plants !hich becomes part of cell !all separates the t!o cells    Go ensre ): is bein- replicated correctly, there are mltiple checpoints& (1 Check&oint # sZcient ntrients, ncleotides, starts choosin- to -et ready for mitosis (2  Check&oint  # checs all ): for mitosis has been replicated properly ) /metaphase Check&oint # ensres all chromosomes are connected to spindles before anaphase commences A&o&tosis is pro-rammed cell death !hich removes n!anted cells /!ebbin- bet!een di-its drin- embryo development, sheddin- of leaves provides protection a-ainst cold and recycles ntrients, removal of dama-ed cells, disinte-ration of  tadpoleFs tail for recyclin-. man somatic cells have 46 chromosomes /n # diploid !hilst -ametes /sperm and ova have 3 /n # haploid so !hen they fse drin- fertilisation they mae n. Ghe process of prodcin- a haploid cell is meiosis, !hich has t!o sta-es, the second of !hich is near identical to mitosis /n4n /a tetrad of each chromosome pairnn&   +nter&hase # as !ith mitosis, ho!ever instead of one dyad /dplicatin- each chromosome a tetrad /t!o dyads is formed )eiosis + -ro&hase + # homolo-os chromosomes /as o dyads come to-ether and synapse /closely apply themselves to each otherA the chromosomes shorten and thicen, and !ithin the tetrad a ladderlie protein strctre /synaptonemal comple7 ali-ns the pair and they cross over to • • • • • 2a-e 6 ?liver o-danovsi • form chiasma /s!aps -enes, increases -enetic diversityA the centrioles move to opposite poles of  the ncles and the nclear membrane breas do!n o   )eta&hase + # chromosomes have nt!ined /are clearly t!o dyads and line p in t!o ro!s, !ith homolo-os pairs ne7t to each other Ana&hase + # homolo-os chromosomes are o plled to opposite sides by inetochore microtbles o   !elo&hase + # chromosome homolo-es are at opposite poles, and be-in to reform a nclear membrane /not e7actly part of meiosis # o   Cytokinesis prodces t!o )P2L?P) cells /basically bac to s5are one, bt !ith crossin- over )eiosis ++ o   +nterkinesis  /Pnterphase PP # no ): replication /ho!ever still centrosome replication -ro&hase ++ # as !ith mitosis /incldes o prometaphase ++ # as !ith mitosis /e7cept each o   )eta&hase chromosome is made of one of each homolo-os pair so splittin- chan-es -enetic diversity, rather than a dplication of each sin-le chromosome and splittin- doesnFt chan-e -enetic diversity as already the same Ana&hase ++ # as !ith mitosis o !elo&hase ++ and Cytokinesis # as !ith mitosis o -C' and +ndi"idual 4ariation Pn ""3, hman -enome proIect completed /based on the ): of several people incldin- Dames ;atson and Center, and mltiple 2a-e K ?liver o-danovsi hman -enomes have no! been flly se5enced.  sin-le -ene is one#millionth of the ):, and a virs may inIect its o!n ): /altho-h in only a fe! ot of millions of cells, so the challen-e is to detect the -ene or viral ): in the presence of billions of bases, and this is completed sin- 2%' /polymerase chain reactions. 2%' re5ires& ): polymerase sin-le#stranded ): template # pattern to synthesise from primers # short pieces of ): to add on to /one for pstream, dierent one for do!nstream free ncleotides # to add to the -ro!in- chain /d:G2s=deo7yribncleotide triphosphate heat # separates ): strands /altho-h can denatre en0yme • • • • • :ote that arro!s !ithot lines !ithin them only cover the e7actly len-th of the -ene. ach cycle /prodction of ne! copies resltin- in a doblin- of molecles /, 4, 8, 16\"\. s ): polymerase is denatred at >" o%, the ): polymerase from the thermophile Thermus aquaticus /Ga5 is sed, !hich is stable at >8 o%, bt optimal at K"o%, allo!in- e7tendin- to be done at a hi-her temperatre than annealin- /no! K o% # dia-ram sho!s for normal ): polymerase. ;e no! have atomated 2%' machines that can do >6 samples at once sin- solid states to rapidly increase and decrease temperatre /as common in a moleclar lab as a photocopier is in an oZce. 2%' is incredibly sensitive and specic, tar-etin- only certain -enes, and the electrophoresis can be applied /as ): is sli-htly ne-ative moves to positive electrode, smaller molecles can move thro-h -el mesh more easily and hence move frther, only those replicated !ill be potent eno-h to see after stainin- !ith Horescent that -lo!s in UC !hen bond to ):. Simple se5ence repeats /SS' are short base pair se5ences that repeat many times, !ith a dierent nmber for dierent people. ;ith arond 1", """ SS's, and each bein- ni5e, it is easy to identify a person by their ):. 2%' is sed to amplify each specic 2a-e 8 ?liver o-danovsi SS' bein- analysed sin- primers desi-ned for those SS's and then these bands are compared /only identical t!ins shold have identical patterns. Usin- this, !e can identify people after disasters /as in >+11, comparin- to in, paternity testin- /particlarly !ith celebrity heirs, dedce crime sspects /13 sed by EP, or prove historical trths /nastasia and the 'omanovs. o!ever, this evidence can only be sed for X%LUSP?:, as yo can prove that the SS's donFt line p. Pf they do line p, inclsion cannot be proved as this may be by happenstance. *itchondria also have their o!n ): !hich comes entirely from the mother, !hich !as sed in cases lie identifyin- if nastasia !as still alive by comparin- to another -reat# -randchild of Ween Cictoria. air cannot be sed /as it is Ist protein, no ):, ho!ever hair follicles can be. )utation  mtation is a chan-e in the ncleotide se5ence of an or-anismFs ):, ltimately creatin- -enetic diversity. Ghey can also occr in virs ): or ':. *tations lead to diversity !hich is critical to the srvival of life. Eor e7ample, the ritish 2eppered *oth had a mtation resltin- in some li-ht, some dar, !hich !ere better at camoHa-e in either lichen#covered trees or soot#covered indstrial areas drin- the Pndstrial 'evoltion of the mid#1> th % !hen polltion !as bein- prodced. Ghey !ill only be inherited in osprin- if they occr in -ametes. *tations can occr as& point mtations /chan-es sin-le base insertions deletions dplications of se5ences chromosomal rearran-ements /lie fsion, ssion, inversion and translocation *tations can be cased by&   errors in ): replication /): polymerase maes 1 error in 1"< bases, leadin- to incorrect base#pairin-, ho!ever ): repair en0ymes redce this to 1 in 1" 1" • • • • • •   mutagens /nicotine, asbestos, free radicals, o   chemicals o7idisin- a-ents, ncleotide analo-es !hich dama-e ): o   radiation /natral radiation lie ranim, nclear !aste+bombs, medical X#rays, UC # ", """ pyrimidine dimers /e.-. G#G+hor+cell are cased at 1pm in SydneyFs Smmer !hich dama-es ):   trans&osable ): /Impin- -enes )ama-ed ): /lie the thymine dimers cased by UC #adIacent thymines that bend to!ards each other thro-h #bonds # !hich cases ): to bcle de to their pll to!ards each other • • 2a-e > ?liver o-danovsi and hence interfere !ith replication can be repaired to ensre transcription is not problematic and -ene e7pression occrs correctly. 'epair is done sin- a nclease en0yme that cts the dama-ed ): at t!o point arond the area of dama-e, and then this is removed. ): polymerase then lls in the remaininncleotides /from the ? of the previos one, and ): li-ase seals this to the follo!in- strand. Xeroderma pi-mentosm /%2 is an inherited defect in a ): dama-e repair en0yme, resltin- in individals that are hypersensitive to snli-ht /canFt correct thymine dimers, !hich can reslt in silencin- tmor sppression -enes and lead to sin cancer. *ost ): chan-es are otside of -enes, !hich often doesnFt have any eect on the nal reslt, ho!ever there are many re-latory -enes otside codin- re-ions and hence they can still have lar-e eects on -ene e7pression. Ghese chan-es can have three otcomes !ithin e7ons& :o eect # reslts in dierent codon that reslts in same amino acid *issense # chan-es amino acid :onsense # chan-es amino acid to stop Erameshift # insertion+deletion of amino acids not a mltiple of  three !ill chan-e all amino acids do!nstream /may introdce missense or nonsenseA if it is a mltiple of three, it is simply the -ain or loss of amino acids. Ghis cold reslt in chan-in- the tertiary strctre of the protein dependin- on the side chain properties of  the amino acid /char-e, shape and ho! dierent this is to !hat it !as beforeA other!ise there may be no chan-e. Ghose that do chan-e may lose some or all fnctionality, or cold -ain a ne! activity. Pf the amino acid is !here the sbstrate or cofactor binds it !ill liely have a -reater eect than if else!here on the protein. Sin-le base chan-es are the most common variants /J8&3&3&1 in dihybrid crosses )echanisms of +nheritance ntin-tonFs disease /neral de-eneration is an e7ample of  an atosomal dominant /<"N of inheritance if one parent has it, aects both sons and da-hters, !hilst an X#lined recessive !old be haemophilia /!hich can only occr in X aXa /rare or X a ], bt never anyone !ith X. *itochondria are maternally inherited or-anelles carryin- their o!n -enes, and an e7ample of a disease is 9earns# Sayre syndrome, !hich cases a short statre and retinal de-eneration. ?ccasionally homolo-os chromosomes donFt separate drinmeiosis /non.dis7unction, resltin- in n#1 or n@1 haploids and aneploidy in the diploids /n#1 or n@1 chromosomes. Eor e7ample, )o!n syndrome /trisomy#1, 9linefelter syndrome /XX]  -enerally fairly normal, the second X bein- trned o as if they !ere female prodcin- a male, and  Grner syndrome /monosomy X  severe in hmans, not so mch in mice. *endelFs second la! of  independent assortment !as formlated !ithot the no!led-e that -enes occr on chromosomes, so if t!o -enes are near each other on the same chromosome, the la! breas do!n /evidenced by a dihybrid testcross of drosophila prodcina phenotypic ratio of <&<&1&1 instead of 1&1&1&1. 'ecombination is Ist the rearran-ement of -enetic material, particlarly by crossinover or articial Ioinin- of ): se-ments.  Ghis ratio occrs becase the loci+-enes are lined on the same chromosome and the closer the loci, the lo!er the chance of recombination. ;e can reverse this 2a-e 3 ?liver o-danovsi /the fe!er recombinants in a testcross, the closer the -enes, !ith the percenta-e of osprin- bein- recombinants bein- the relative distance /in the above e7ample 1KN. Ghe ma7imm recombination is <"N /after !hich point it is more liely the -enes are on separate chromosomes and the complementary percenta-e is the percenta-e of recombination. So a "N chance of recombination means recombinants are impossible, !hilst 