How do we know that specific genes are located on the s chromosomes rather than

Question

How do we know that specific genes are located on the s chromosomes rather than on autosomes? Drag the terms on the left to the appropriate blanks on the right to complete the sentences. normal reciprocal monohybrid similarities mutant trihybrid X Y differences The sex of the parent carrying a allele influenced the results of crosses when compared to a cross. When correlated with the sex chromosome between males and females, a model placing a gene on the chromosome was supported. Since the chromosome lacks homology with almost all genes on the chromosome, these alleles present on the chromosome of the males will be directly expressed in the phenotype.

Explanation / Answer

The sex of the parent carrying a mutant allele influenced the results of crosses when compared to a reciprocal cross.

When correlated with the sex chromosome, differences between males and females, a model placing a gene on the X chromosome was supported.

Since the Y chromosome lacks homology with almost all genes on the X chromosome, these alleles present on X chromosome of males will be directly expressed in the phenotype.

In humans, the sex and location of specific genes are found by XX/XY sex determination system. In this system, females have two same kinds of chromosomes i.e XX. and males have two different kinds of chromosomes i.e XY. The X and Y chromosomes are different in shape and size from each other. Y chromosomes do not have the copies of most genes that are found on the X chromosome. Therefore, X chromosomal based genes exhibit patterns of inheritance that are completely different from the inheritance patterns of autosomal genes.
In 1910, Thomas H. Morgan demonstrated the fist case of X-linkage in Drosophila melanogaster. The inheritance pattern of eye color was related to the sex of the parent by performing reciprocal crosses. He showed that when a white-eyed male (mutant type allele) is crossed with a red-eyed female (wild-type allele), only red-eyed offspring are produced but a cross between a red-eyed male and a white-eyed female, white eyed male offspring and red eyed female offspring are produced. This cleared that white eye allele was sex-linked (i.e this allele was present on the X-chromosome rather than on autosomes) and recessive. This means that phenotypic changes are dependent on the white eye allele (mutant allele).

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