Question

1. in horses, coat color black (b) is dominant over chestnut (b). the trotting gait is dominant (t) over the pacing gait (t). if a homozygous black pacer is mated to a homozygous chestnut, heterozygous trotter, what will be the genotypes and phenotypes of the offspring? show your work in the form of a punnett square and write your answers as a phenotypic ratio.

Explanation:

Step1: Identify parent genotypes

Homozygous black pacer: $BBtt$; Homozygous chestnut heterozygous trotter: $bbTt$

Step2: List gametes for each parent

Gametes from $BBtt$: $Bt$; Gametes from $bbTt$: $bT, bt$

Step3: Fill Punnett Square

	$Bt$	$Bt$	$Bt$	$Bt$
$bt$	$Bbtt$	$Bbtt$	$Bbtt$	$Bbtt$
$bT$	$BbTt$	$BbTt$	$BbTt$	$BbTt$
$bt$	$Bbtt$	$Bbtt$	$Bbtt$	$Bbtt$

Step4: Count genotypes and phenotypes

Genotypes: $BbTt$ (8), $Bbtt$ (8); Phenotypes: Black trotter ($BbTt$), Black pacer ($Bbtt$)

Step5: Calculate phenotypic ratio

Ratio of black trotter to black pacer: $\frac{8}{16}:\frac{8}{16} = 1:1$

Answer:

Genotypes of offspring: $BbTt$, $Bbtt$

Phenotypic ratio: 1 Black trotter : 1 Black pacer