Question

6. In goats, beards are produced by an autosomal allele that is expressed differently in males and females: The bearded allele (Bº) is dominant over the beardless allele (B") in males, but recessive in females. Therefore, males only need one copy of the bearded allele to be bearded, but females need two copies of the bearded allele to be bearded. Another independently assorting autosomal allele determines coat color: black coat (L) is completely dominant over white coat (1). For each of the following crosses, give the phenotype ratios you'd expect to see in the offspring (there are 8 possible phenotype classes: bearded black males, bearded white males, beardless black males, beardless white males, bearded black females, bearded white females, beardless black females, and beardless white females). Show your work. a) Bºb" Ll male X B"B" Ll female b) B"B" Ll male X B'Bli female c) B"B" Lil male X B'Bºll female

Answer 1

B^B is dominant over Bⁿ allele in males .

therefore B^BB^B male = bearded male and also B^BBⁿ male = bearded male and only BⁿBⁿ male is beard less male

but B^B is recessive in females

therefore B^BB^B female = bearded female , and B^BBⁿ female = beard less female , also BⁿBⁿfemale = beard less female .

black coat ( L ) is completely dominant over white coat (l) therefore LL genotype = black coat, Ll genotype = black coat , and only ll genotype= white coat

a) B^BBⁿ Ll male cross with B^BBⁿ Ll female

a) por (Bearded Ll black male mate) x B 8h Ll female (Beardless black female) gamets I gamets. Bol, Bre, &ul, bre 8L sre, BL, pre Bearded, black Bearded, black BB, le B Brel BB kr Le BB Bull EPL SPELL DELL HE'LL BE"le ਵਾਹ EL CELL OPE'LL SE'LL APPLE En e pepe L L cBe'll Bence This is a dihyderid cross. i) B² BB LL = Bearded belack (Both male, female) ii) BB Br LL = Bearded black male and beard less belack 1 RB Br Le Bearded black male and beard less black female in en Br LL = Beard less black (Both male, female) v pngh Le - Beard less black (Both male, temale) vi B B B ll & Bearded white (Both male, female) & Bearded .) BB Brll male white and Beard less white female Vill) BBB Le - Bearded belack (Both male, temale female (only feased on external cherecto

total bearded black male = 9 among 16 ( there are total 16 genotype we assume that there are one male and one female of each genotype i.e there are total 32 offspring among which 16 are male and 16 are female of same genotype  ) , total bearded white male = 3 among 16, total beard less black male= 3 among 16, and beard less white male =1 among 16 .

and total bearded black female= 3 among 16 , total bearded white female = 1 among 16 , total beard less black female= 9 among 16 and beard less white female = 3 among 16  

phenotypic ratio will be such as follow

bearded black male: bearded black female : beard less black male : beard less black female : Bearded white male : bearded white female : beardless white male : beard less white female = 9: 3: 3: 9: 3: 1: 1:3   

b) BⁿBⁿ Ll male cross with B^BB^B Ll female

x 8" 8h Le male guante gamets BhL, srl Bege e female. gamets B&L Bel BYL Bre BⓇL Beg" LL BE 8 Le Be e Bene Bell . Bn. n B²B LL = Black Black Bearded beard less male female male female Beer Le = Black, black Bearded beard less = Bearded Beard less White White male female. BB ll

it is also a dihybrid cross but only 4 types of phenotypic charecter will be seen and here we also assume that each genotype is carried by one male and one female there fore

total bearded black male = 3 among 4 ( 12 among 16) and , beardless black male = 0 among 4 (0 among 16) , bearded white male = 1 among 4  ( 4 among 16 ) and beard less white male = 0 among 4 ( 0 among 16 )

and black bearded female 0 among 4 ( 0 among 16 ) black beard less female = 3 among 4 ( 12 among 16 ) , white bearded female = 0 among 4 ( 0 among 16 ) and beard less white female = 1 among 4 ( 4 among 16) there fore the phenotypic ratio will be

bearded black male : bearded black female: bearded white male : bearded white female : beard less black male : beard less black female : beard less white male : beard less white female = 3: 0: 1 : 0 : 0: 3 : 0: 1

c) B^BBⁿ Ll male cross with B^BB^B ll female

Bn B B ll female B B gamets Bel Le male & ! Bre, & L, 8l x gamets Bel & B B B B B B n. B B L l B B ll BBL el BB ll. B B Le = Black bearded (Both male, female - BB B B ll Bn BB" Le (Both male, female male temale White, bearded Black bearded black beard less = Bn B Blu White bearded white, beard less male female ley one male and among 4 e o pe will Carried one female Cassume) Total Black beareded male = 2 Total Black bearded female = 1 black beard less male = 0 black beard Total female = less 1 bearded white a male s white beard less male Total White bearded temale = 1 Total white beard les temale I among a among a among 4 among a Total Total among a 3) among a

there fore the phenotypic ratio will be 2:1:0:1:2:0:1:1