In rats, gene B produces a black color if the genotype is B-, but the black pigm
ID: 55795 • Letter: I
Question
In rats, gene B produces a black color if the genotype is B-, but the black pigment is not produced if the genotype is bb. At an independent locus, gene D produces a yellow pigment if the genotype is D-, but no pigment is produced when the genotype is dd. Production of both pigments results in a brown color. If neither pigment is produced, coat color is cream. Determine the genotypes of parents of litters with the following phenotype distributions.
Enter your answers separated by a comma. ( for example, for BBDD and BbDd, enter BBDD,BbDd)
1. 9 Black and 9 Cream.
Explanation / Answer
In rats, gene B produces black coat color if the genoptye is B -, but black pigment is not produced if the genotype is bb .
At an independent locus, gene D produces yellow pigment if the genotype is D -, but no pigment is produced when the genotype is dd .
Production of both pigments results in brown coat color. If neither pigment is produced, coat color is cream.
.a. 1 brown: 1 black: 1 yellow: 1 cream -For gene B:
1 parent must be Bb and the other bb -For gene D:
1 parent must be Dd and the other dd
b. 3 brown: 3 yellow: 1 black: 1 cream
CROSS BETWEEN PARENTS OF ALLELS BbDd x bbDd
.
If a rat is BB or Bb, it will have a black coat unless it also is DD or Dd (in which case it will be cream), and the same reasoning allows us to figure out what a bb rat's coat color will be... So, rats with black coats are...
BBDD = Brown coat
BBDd = Brown coat
BBdd = black coat
BbDD = Brown coat
BbDd = Brown coat
Bbdd = black coat
bbDD = yellow coat
bbDd = yellow coat
bbdd = cream coat
Basically, if there's a bit B and a big D, it's brown. A big B but no big D means it's black. A big D but no big b means it's yellow. And a little b and a little d means it's cream.
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