AVIAN GENETICS

AVIAN GENETICS

SEX-LINKED AND AUTOSOMAL GENE COMBINATIONS

Most breeding crosses are made between parents containing multiple mutations. In this section, I will address a cross involving both a sex-linked mutation and an autosomal mutation.

PLEASE NOTE

The X and Y portrayed in the Punnett squares below represent the sex chromosomes and any allele in superscript is sex-linked. The autosomal allele is not written in superscript - it is written in normal script. The autosomal genes are not attached to the sex chromosomes but rather are grouped with the respective sex chromosome during gamete formation.

The following presents a worst case scenario (i.e., requires the most calculations) for a sex-linked and autosomal mutation cross. A Normal Male heterozygous for Opaline and Pied (X^op,X⁺,+,r) is crossed to a hemizygous Normal Female heterozygous for Pied (X⁺,Y,+,r). The four possibilities of gametes the male can produce are as follows:

X^op, r and X⁺, +

X^op, + and X⁺, r

The four possibilities of gametes the female can produce are as follows:

X⁺, r and Y, +

X⁺, + and Y, r

In this case there are four different crosses that would have to be performed to derive the expected outcome. These crosses are as follows:

	Male		Female
Case 1	X^op, r and X⁺, +	crossed to	X⁺, r and Y, +
Case 2	X^op, r and X⁺, +	crossed to	X⁺, + and Y, r
Case 3	X^op, + and X⁺, r	crossed to	X⁺, r and Y, +
Case 4	X^op, + and X⁺, r	crossed to	X⁺, + and Y, r

Figures 11 through 14 work through each case. Since each case has the same probability of occurrence, the expected total outcome (i.e., the summation of Figures 11 through 14) of this breeding can be summarized as follows:

1/16 Pied /opaline Males

1/8 Normal /pied Males

1/8 Opaline /pied Females

1/16 Normal Females

1/8 Normal /pied/opaline Males

1/16 Normal Males

1/16 Opaline Pied Females

1/8 Normal /pied Females

1/16 Pied Males

1/16 Opaline Females

1/16 Normal /opaline Males

1/16 Pied Females

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