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In Guinea pigs, black hair (B) is dominant over white (b), rough coat texture (R) is dominant over smooth (r), and short hair (S) is dominant over long hair (s). Assuming these genes are on separate chromosomes, draw the Punnett square for a cross between a heterozygous BLACK, ROUGH, SHORT haired with another heterozygous BLACK, ROUGH, SHORT haired guinea pig. What is the PHENOTYPIC RATIO of the offspring

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marianaegarciaperedo

Answer:

Phenotypic ratio: 27:9:9:9:3:3:3:1

Explanation:

Available data:

  • black hair (B) is dominant over white (b)
  • rough coat texture (R) is dominant over smooth (r)
  • short hair (S) is dominant over long hair (s)
  • genes are on separate chromosomes
  • Cross: heterozygous BLACK, ROUGH, SHORT haired with another heterozygous BLACK, ROUGH, SHORT haired guinea pig

Parentals) BbRrSs    x     BbRrSs

Gametes) BRS, BRs, BrS, Brs, bRS, bRs, brS, brs

                BRS, BRs, BrS, Brs, bRS, bRs, brS, brs

Punnett square)

         BRS         BRs          BrS         Brs         bRS         bRs         brS         brs

BRS BBRRSS  BBRRSs  BBRrSS  BBRrSs  BbRRSS  BbRRSs  BbRrSS  BbRrSs

BRs  BBRRSs  BBRRss  BBRrSs   BBRrss  BbRRSs   BbRRss  BbRrSs   BbRrss

BrS   BBRrSS  BBRrSs   BBrrSS    BBrrSs   BbRrSS  BbRrSs   BbrrSS    BbrrSs

Brs   BBRrSs   BBRrss    BBrrSs    BBrrss    BbRrSs   BbRrss   BbrrSs    Bbrrss

bRS BbRRSS  BbRRSs  BbRrSS  BbRrSs   bbRRSS  bbRRSs  bbRrSS  bbRrSs

bRs  BbRRSs   BbRRss  BbRrSs   BbRrss   bbRRSs  bbRRss  bbRrSs   bbRrss

brS  BbRrSS    BbRrSs   BbrrSS    BbrrSs   bbRrSS   bbRrSs   bbrrSS   bbrrSs

brs  BbRrSs     BbRrss    BbrrSs    Bbrrss    bbRrSs   bbRrss    bbrrSs   bbrrss

F1)  Phenotype

     27/64 B-R-S-  

     9/64 B-rrS-

     9/64 B-R-ss

     9/64 bbR-S-

     3/64 B-rrss

     3/64 bbrrS-

     3/64 bbR-ss

     1/64 bbrrss    

Note: The symbol "-" represents either dominant or recessive alleles.

Phenotypic ratio: 27:9:9:9:3:3:3:1

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