Chapter 5.1, Problem 21AQP

Summary Introduction

To examine:

The cross between black and bronze plumage.

Introduction:

Plumage refers to the colored pattern or the layer of father that cover a bird, including the arrangement of the feathers. In different species or subspecies of birds the pattern and color of plumage are varied. The colors of plumage include black and bronze. The alleles for the black color is ${\text{B}}^{\text{L}}$, and the allele for the bronze color is ${\text{B}}^{\text{R}}$. The allele ${\text{B}}^{\text{L}}$ is dominant over ${\text{B}}^{\text{R}}$.

Explanation of Solution

A cross between the ${\text{black (B}}^{\text{L}}{\text{B}}^{\text{L}}{\text{) × bronze (B}}^{\text{R}}{\text{B}}^{\text{R}}\text{)}$ plumages:

	$B^R$	$B^R$
$B^L$	$\begin{array}{l}{\text{ B}}^{\text{L}}{\text{B}}^{\text{R}}\\ \text{(Black)}\end{array}$	$\begin{array}{l}{\text{ B}}^{\text{L}}{\text{B}}^{\text{R}}\\ \text{(Black)}\end{array}$
$B^L$	$\begin{array}{l}{\text{ B}}^{\text{L}}{\text{B}}^{\text{R}}\\ \text{(Black)}\end{array}$	$\begin{array}{l}{\text{ B}}^{\text{L}}{\text{B}}^{\text{R}}\\ \text{(Black)}\end{array}$

A cross between ${\text{black (B}}^{\text{L}}{\text{B}}^{\text{L}}{\text{) × bronze (B}}^{\text{R}}{\text{B}}^{\text{R}}\text{)}$ gives all black color plumage because ${\text{B}}^{\text{L}}$ allele for black color is dominant over the ${\text{B}}^{\text{R}}$ allele of the bronze color.

Summary Introduction

To examine:

The cross between black and black plumage.

Introduction:

The colors of plumage include black and bronze. The alleles for the black color is ${\text{B}}^{\text{L}}$, and the allele for the bronze color is ${\text{B}}^{\text{R}}$. The allele ${\text{B}}^{\text{L}}$ is dominant over ${\text{B}}^{\text{R}}$. Plumage refers to the colored pattern or the layer of father that cover a bird, including the arrangement of the feathers.

Explanation of Solution

A cross between the ${\text{black (B}}^{\text{L}}{\text{B}}^{\text{R}}{\text{) × black (B}}^{\text{L}}{\text{B}}^{\text{R}}\text{)}$ plumages:

	$B^L$	$B^R$
$B^L$	$\begin{array}{l}{\text{ B}}^{\text{L}}{\text{B}}^{\text{L}}\\ \text{(Black)}\end{array}$	$\begin{array}{l}{\text{ B}}^{\text{L}}{\text{B}}^{\text{R}}\\ \text{(Black)}\end{array}$
$B^R$	$\begin{array}{l}{\text{ B}}^{\text{L}}{\text{B}}^{\text{R}}\\ \text{(Black)}\end{array}$	$\begin{array}{l}{\text{ B}}^{\text{R}}{\text{B}}^{\text{R}}\\ \text{(Bronze)}\end{array}$

The obtained genotypic ratio is 3:1.

The obtained phenotypic ratio is 3:1.

A cross between ${\text{black (B}}^{\text{L}}{\text{B}}^{\text{R}}{\text{) × black (B}}^{\text{L}}{\text{B}}^{\text{R}}\text{)}$ gives the 3:1 ratio, which suggests that ¾ offspring are black and ¼ offspring is bronze. Both the parents are present in heterozygous condition in which ${\text{B}}^{\text{L}}$ allele for black color is dominant over the ${\text{B}}^{\text{R}}$ allele.

Summary Introduction

To examine:

The cross between black-bronze and black-bronze plumage.

Introduction:

The allele for the bronze color is ${\text{B}}^{\text{R}}$ The alleles for the black color is ${\text{B}}^{\text{L}}$, and the alleles for the black bronze is $bb$ Plumage is the layer of feathers with different colored patterns that cover a bird, including the arrangement of the feathers.

Explanation of Solution

A cross between the $\text{black-bronze (bb) × black-bronze (bb)}$

	$b$	$b$
$b$	$\begin{array}{l}\text{ bb}\\ \text{(Black-bronze)}\end{array}$	$\begin{array}{l}\text{ bb}\\ \text{(Black-bronze)}\end{array}$
$b$	$\begin{array}{l}\text{ bb}\\ \text{(Black-bronze)}\end{array}$	$\begin{array}{l}\text{ bb}\\ \text{(Black-bronze)}\end{array}$

A cross between $\text{black-bronze (bb) × black-bronze (bb)}$ gives all black-bronze color plumage. A black-brown color is expressed by a homozygous recessive allele.

Summary Introduction

To examine:

The cross between black and-bronze color plumage.

Introduction:

Plumage is the layer of feathers with different colored patterns that cover a bird, including the arrangement of the feathers. The alleles for the black color is ${\text{B}}^{\text{L}}$, and the allele for the bronze color is ${\text{B}}^{\text{R}}$. The allele ${\text{B}}^{\text{L}}$ is dominant over ${\text{B}}^{\text{R}}$.

Explanation of Solution

A cross between the ${\text{black (B}}^{\text{L}}{\text{b) × bronze (B}}^{\text{R}}\text{b)}$

	$B^R$	$b$
$B^L$	$\begin{array}{l}{\text{ B}}^{\text{L}}{\text{B}}^{\text{R}}\\ \text{ (Black)}\end{array}$	$\begin{array}{l}{\text{ B}}^L\text{b}\\ \text{ (Black)}\end{array}$
$b$	$\begin{array}{l}{\text{ B}}^R\text{b}\\ \text{ (Bronze)}\end{array}$	$\begin{array}{l}\text{ bb}\\ \text{(Black-bronze)}\end{array}$

The obtained genotypic ratio is 1:1:1:1

The obtained phenotypic ratio is 1:2:1 (bronze:black:black-bronze)

A cross between ${\text{black (B}}^{\text{L}}{\text{b) × bronze (B}}^{\text{R}}\text{b)}$ gives ½ black offspring, ¼ bronze, and ¼ black-bronze. The parents are present in heterozygous condition that contain one recessive allele of the black-brown color.

Summary Introduction

To examine: The cross between bronze and-black-bronze plumage.

Introduction:

In different species or subspecies of birds the pattern and color of plumage are varied. The colors of plumage include black and bronze. The alleles for the black color is ${\text{B}}^{\text{L}}$, and the allele for the bronze color is ${\text{B}}^{\text{R}}$. The allele ${\text{B}}^{\text{L}}$ is dominant over ${\text{B}}^{\text{R}}$.

Explanation of Solution

A cross between the ${\text{bronze (B}}^{\text{R}}\text{b) × black-bronze (bb)}$ plumage

	$b$	$b$
$B^R$	$\begin{array}{l}{\text{ B}}^R\text{b}\\ \text{ (Bronze)}\end{array}$	$\begin{array}{l}{\text{ B}}^R\text{b}\\ \text{ (Bronze)}\end{array}$
$b$	$\begin{array}{l}\text{ bb}\\ \text{(Black-bronze)}\end{array}$	$\begin{array}{l}\text{ bb}\\ \text{(Black-bronze)}\end{array}$

The obtained genotypic ratio is 1:1

The obtained phenotypic ratio is 1:1 (bronze : black-bronze)

A cross between ${\text{bronze (B}}^{\text{R}}\text{b) × black-bronze (bb)}$ gives ½ bronze offspring and ½ black-bronze. These offspring are derived from a heterozygous and homozygous recessive parents.

Summary Introduction

To examine:

The cross between bronze and bronze plumage.

Introduction:

The colors of plumage include black and bronze. The alleles for the black color is ${\text{B}}^{\text{L}}$, and the allele for the bronze color is ${\text{B}}^{\text{R}}$. The allele ${\text{B}}^{\text{L}}$ is dominant over ${\text{B}}^{\text{R}}$. Plumage refers to the colored pattern or the layer of father that cover a bird, including the arrangement of the feathers.

Explanation of Solution

A cross between the $bronze(B^{R}b)\times bronze(B^{R}b)$ plumages

	$B^R$	$b$
$B^R$	$\begin{array}{l}{\text{ B}}^{\text{R}}{\text{B}}^{\text{R}}\\ \text{ (Bronze)}\end{array}$	$\begin{array}{l}{\text{ B}}^R\text{b}\\ \text{ (Bronze)}\end{array}$
$b$	$\begin{array}{l}{\text{ B}}^R\text{b}\\ \text{ (Bronze)}\end{array}$	$\begin{array}{l}\text{ bb}\\ \text{(Black-bronze)}\end{array}$

The obtained genotypic ratio is 1:2:1

The obtained phenotypic ratio is 3:1 (bronze : black-bronze)

A cross between $bronze(B^{R}b)\times bronze(B^{R}b)$ gives 3/4 bronze offspring, and 1/4  black-bronze. These offspring are derived from the heterozygous parents with a recessive alleles.

Summary Introduction

To explain:

Whether these differences in plumage arise from incomplete dominance or not.

Introduction:

When one of the paired alleles does not completely express itself for a particular phenotype is called incomplete dominance. Plumage refers to the colored pattern or the layer of father that cover a bird, including the arrangement of the feathers.

Explanation of Solution

Incomplete dominance is the phenomenon in which one of the alleles for specific phenotype is not completely expressed. These differences in plumage arise from the incomplete dominance because the allele for the bronze color (${\text{B}}^{\text{R}}$) is not expressed completely over its paired allele.

Symbols for alleles:

$B^R$ for bronze color.

$B^L$ for black color

$b$ for black-bronze color.

Genotype of turkeys:

Cross 1: ${\text{The genotype is black (B}}^{\text{L}}{\text{B}}^{\text{L}}{\text{) and bronze (B}}^{\text{R}}{\text{B}}^{\text{R}}\text{)}$

Cross 2: ${\text{The genotype is black (B}}^{\text{L}}{\text{B}}^{\text{R}}{\text{) and black (B}}^{\text{L}}{\text{B}}^{\text{R}}\text{)}$

Cross 3: $\text{The genotype is black-bronze (bb) and black-bronze (bb)}$

Cross 4: ${\text{The genotype is black (B}}^{\text{L}}{\text{b) and bronze (B}}^{\text{R}}\text{b)}$

Cross 5:${\text{The genotype is bronze (B}}^{\text{R}}\text{b) and black-bronze (bb)}$

Cross 6: ${\text{The genotype is bronze(B}}^{\text{R}}{\text{b) and bronze(B}}^{\text{R}}\text{b)}$

Conclusion

Hence, the result of cross 1 shows that all plumages are of black color. The result of cross 2 shows that black is dominant over bronze color in the ratio of 3:1. The result of cross 3 shows that all plumages are of black-brown color. The result of cross 4 shows that ½ offspring are black, ¼ offspring are bronze, and ¼ offspring are black-bronze. The result of the cross 5 shows that half of the offsprings are bronze and half are black bronze. The result of cross 6 shows that ¾ offspring is bronze and ¼ fourth are black-bronze.