BIOL 3301 - Genetics Ch4B - Gene Interaction St

8/18/2019 BIOL 3301 - Genetics Ch4B - Gene Interaction St

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Gene Interaction


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Color Variants In Chicken

• 1902, Bateson – Dominant white color inchicken

• Is determined by gene I, ___________________________________

• ___________________ to ild ty!e allele I• "hird allele #moky gi$es a grayish

!henoty!e, recessi$e to Dominant white


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%odi&ications o& 'ihybrid Cross

• Gene interaction – (rod)ction o& a ne ___________________

– *!istasis, +stand abo$e – one gene _______________________ the e&&ect o&another gene -e!istatic $s hy!ostatic.

– " o gene !airs can com!lement one another –at least one _______________________ ateach loc)s is re/)ired to e !ress a !artic)lar

!henoty!e


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Gene Interaction

(rod)ction o& ne !henoty!es


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Comb #ha!e In Chicken

( rose single !ea single1 rose !ea2

( rose !ea

1 walnut 2


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*!istasis

Interaction bet een t o or moregenes to control a single !henoty!e3

4ne gene can mask the !henoty!ice !ression o& another –

_____________________________


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%echanisms o& *!istasis

• aa masks B – ____________________ • 56 masks B6 6 ___________________

– 5 gene that masks – e!istatic – 5 gene that is masked 6 hy!ostatic


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7ecessi$e *!istasis

• 56bb and aabb ha$e the __________________

• 2 ratio ______________________


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Coat Color In 7odents

ild ty!e – ago)ti -hair in &)r ha$ealternating bands o& black and yello .albino – hite mice

ago)ti 8 black8 albino


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( ago)ti albino55CC aacc

1 ago)ti5aCc

2 9 ago)ti black : albino

(resence o& cc ill al ays res)lt in ________


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• 5 cross bet een t o black mice that arehetero;ygo)s -BbCc. ill &ollo the la o&

inde!endent assortment3•


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Coat color in mice

56 6 ago)ti= aa – non6ago)ti• B6 6 black, bb – bro n

• non6%endelian 9 : ratio o& !henoty!es .• Recessive

epistasis5B 5b aB ab

5B5b

aB

ab


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• 5ct)ally, three genes – C – allo s !igment &ormation

– cc – !re$ent !igment &ormation – 5 – ago)ti – aa – non6ago)ti

– B – black !igment – bb – bro n !igment(re$io)s cross _____________________


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Coat color in mice biochemical

basis

Gene B Gene 5

(rec)rsor black !igment ago)ti

B6 56


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Coat Color In >abradors

B – black !igment bb – bro n !igment

* – allo s color -___________________.ee – does not allo color - ______________. –

yello

B6*6 black bb*6 bro n66 ee – yello -B6ee – dark nose and li!s.


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Coat Color In >abradors

( BB** bbee12 9 black bro n : yello


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Coat Color In %ammals

• "he 5 gene – ago)ti, band o& yello on the hairsha&t= -5? , 5 t –black and tan.= aa – solid

• "he B gene – – B – ago)ti ith 5= – ith aa – solid black3 – 56bb – cinnamon or bro n= – aaB6 6 solid black= – aabb – solid bro n

• "he C gene – C allele ___________= cc – !re$entscolor – e!istatic to other color genes


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Coat Color In %ammals

• "he ' gene – modi&ier gene= controls theintensity o& !igment s!eci&ied by other color

genes – '6 !ermits &)ll color – 'd – dil)te color to milky a!!earance

• "he # gene – !resence and absence o& s!ots – #6 6 no s!ots= ss 6 s!ots


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'ominant *!istasis

• 56B6 and 56bb ha$e the same !henoty!e• 2 ratio is _____________________


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r)it Color 4& #)mmer #/)ash

• @hite, yello , green( @hite yello hite green yello green

1 hite hite yello@hite 8 yello 8 green@6 hite -@6?6= @6yy.

– allo color ?6 – _______________ yy 6 ________________


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*!istasis In$ol$ing ')!licate Genes• # eat !ea()r!le hite !)r!le6 1 !)r!le hite@hite hite hite

@hite hite all !)r!le ________________ C – allo s color cc – _______________( – !)r!le

!! – ________________')!licate recessi$e e!istasis or com!lementary gene action


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9 A 7atio -Com!lementary Gene 5ction.

Example lo er color in s eet !eaEnzyme Pathway

GeneC

Gene P

*n;yme C *n;yme P Precursor Intermediate Anthocyanin


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The Cross And The Results

Parental Cross Colored &lo ers - CCPP . @hite &lo ers - ccpp .

F Colored lo ers

F ! 9 Colored lo ers A lo ers


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The Genotypes And Their RespectivePhenotypes

Genotype

Flower color Enzyme activities

9 C_P_ lo ers colored= anthocyanin !rod)ced

&)nctional en;ymes &rom both genes

C_pp lo ers hite= no anthocyanin !rod)ced

p en;yme non6&)nctional

ccP_ lo ers hite= no anthocyanin !rod)ced

c en;yme non6&)nctional

1 ccpp lo ers hite= no anthocyanin !rod)ced

c and p en;ymes non6&)nctional

Beca)se both genes are re/)ired &or the correct !henoty!e, this e!istatiinteraction is called complementary "ene action 3


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')!licate 'ominant *!istasis

#he!herd !)rse !lant – &r)it sha!e


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%odi&ied 'ihybrid %endelian 7atios

(rod)ced By Gene Interaction


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• @hen a _____________ is controlled by morethan one gene e!istasis may res)lt

• nderstanding biochemical !ath ays hel!s )s)nderstand e!istasis

*!istasis

B CA 21 DC

A 3

1

D2B


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*!istasis

B CA 21

• I& the gene &or en;yme 1 as knocked o)t, the&lo er o)ld be colorless

B CA 21

X

• Imagine that this !ath ay !rod)ces a red !igment,C, in &lo ers and that 5 is a colorless !rec)rsorand B is a yello intermediate


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*!istasis

B CA 21

• I& the gene &or en;yme 1 as knocked o)t, the&lo er o)ld be colorless

B CA 21

X

• Imagine that this !ath ay !rod)ces a red !igment,C, in &lo ers and that 5 is a colorless !rec)rsorand B is a yello intermediate

• I& the gene &or en;yme 2 as knocked o)t, the

&lo ers o)ld be yello


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*!istasis

B CA 21

• Beca)se en;ymes can cataly;e many reactions in a short !eriod o& time, the !resence o& H)st one co!y o& a gene isty!ically eno)gh to mask the absence o& a bad co!y

• "h)s an indi$id)al hetero;ygo)s &or en;yme 1 co)ld still !rod)ce intermediate !rod)ct B

B CA 21X X

• I& both genes ere knocked o)t, the &lo ers o)ld be colorless


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Gene Interaction

• *ye color in 'roso!hila – one character,eye color, 9 1 ratio

• ( bro n scarlet= 1 – red - ild ty!e.= 2

b c b c bc bc

b c ild ild ild ild

b c ild scarlet ild scarlet

bc ild ild bro n bro n

bc ild scarlet bro n hite


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*ye color in 'roso!hila –

biochemical basis• (igments – droso!terin -red. and

anthommatin -bro n.

• Bro n eye –bb 6 droso!terin !ath ay isinterr)!ted

• #carlet eye – cc – anthommatin !ath ay isinterr)!ted

• 'o)ble recessi$e bbcc 6F


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Jey (oints

• ___________________ may in&l)ence a trait• 5llele is e!istatic to allele o& another gene i& it has

an o$erriding e&&ect _____________________ • 5 gene is !leiotro!ic i& it can in&l)ence many

____________________________________ • "he ratio o& dihybrid cross may change, b)t total

n)mber o& classes _________, can be e !lained by%endel r)les


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4ther &actors In&l)encing

(henoty!es*n$ironmental &actors, e !ressi$ity,

!enetrance


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"em!erat)re e&&ects

• %)tations that are e&&ected by tem!erat)re arecalled

________________________________________ _____________________ - restricti$eK!ermissi$etem!erat)res.

•


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)tritional *&&ects

• )tritional m)tations• %icroorganisms

– (rototro!hs – 5) otro!hs

•


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(henylketon)ria

• (J is determined by a m)tant allele that !rod)ce non&)nctional en;yme – inability to

)tili;e amino acid !henylalanine• Children ith m)tation – die in early age• Can be easily detected by the !resence o&

abnormal en;yme• 'iet ill allo to gro and &)nctionnormally


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• "he !rod)ct o& a genoty!e is generally not arigidly de&ined !henoty!e, b)t a range o&

!henoty!ic !ossibilities, the ################ , that are determined by theen$ironment3 – In some cases the norm o& reaction has no breadth

-&or e am!le, blood ty!e.3• orms o& reactions are broadest &or !olygenic

characters3

– or these multi$actorialcharacters , en$ironmentcontrib)tes to their/)antitati$e nat)re3

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings


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(enetrance and * !ressi$ity

• (enetrance – ______________________________ that

sho at least some degree o& a m)tant !henoty!e

• * !ressi$ity – _____________________

• Genetic backgro)nd – !resence o& s)!ressorgenes= !osition e&&ect


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(* *"75 C*

• the !ro!ortion o& indi$id)als ith a s!eci&icgenoty!e ho mani&est that genoty!e at the

!henoty!ic le$el3• (enetrance L 130 -100M. hen all homo;ygo)s recessi$e indi$id)als e !ress

the recessi$e &orm o& the allele, and all homo;ygo)s dominant indi$id)als andhetero;ygo)s indi$id)als e !ress the alternate &orm o& the allele3

• (enetrance N 130 i& OnotO all homo;ygo)s recessi$e indi$id)als e !ress therecessi$e allele3

*P5%(>*#• Brachydactyly -short digits. in h)mans• e)ro&ibromatosis in h)mans -disease ca)ses t)mor6like gro ths to a!!ear all

o$er the s)r&ace o& the body, i& it is &)lly e !ressed. 3


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*P(7*##IVI"?

• is _____________ to hich a !artic)largenoty!e is e !ressed in the !henoty!e o& a

!artic)lar indi$id)al3• *P5%(>*#

– (olydactyly – (iebald s!otting in beagles dogs ho ha$e the

same genoty!e &or the !iebald loc)s o&tene !ress $ario)s !atterns and total co$erage o&

hite &)r !atches


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(olygenic Inheritance


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• Contin)o)s $ariation $s discontin)o)s$ariation

• Q)antitati$e traits• %)lti!le &actor or m)lti!le gene hy!othesis

– _____________, each indi$id)ally

beha$ing in %endelian &ashion, contrib)teto the !henoty!e in a c)m)lati$e or/)antitati$e ay - additi$e alleles.

5 b 5 BbC i di$id) l


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• 5 cross bet een t o 5aBbCc indi$id)als-intermediate skin shade. o)ld !rod)ceo&&s!ring co$ering a ide range o& shades3 – Indi$id)als ith

intermediate skin shadeso)ld be the most likely

o&&s!ring, b)t $ery lightand $ery dark indi$id)alsare !ossible as ell3

– "he range o& !henoty!es&orms a normaldistrib)tion3

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings


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The $ormula that predicts the num%er o$ "enotypes$rom the num%er o$ "enes is & n -n is the n)mber o&genes3.

"he &ollo ing is the n)mber o& genoty!es &or a selectedn)mber -n. o& genes hich control an arbitrary trait3

' o$ Genes ' o$ Genotypes1 3

2 9

5 243

10 59,049


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'ogs


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'e&inition o& a


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*ye Color * !lained

• "here is no single gene &or an eye color b)t the biggest e&&ect is 4C52 gene

• "his gene controls the amo)nt o& melanin !rod)ced – acco)nts &or abo)t A:M o& total $ariation

• 4C52 is in&l)enced by other genetic com!onents –e !ression o& 4C52 is linked to three singlen)cleotide !olymor!hisms -# (s.

• I& it is "G" in all three locations, U2M o& !eo!le are bl)e6 eyed= one "G" – 21M, no "G" – A3 M

BIOL 3301 - Genetics Ch4B - Gene Interaction St

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