Additional deletion in sex-determining region of human Y chromosome resolves paradox of X,t(Y;22) female

Article Abstract:

The inheritance of the Y chromosome determines if an embryo becomes male. The male-determining function has been localized to a segment of deoxyribose nucleic acid (DNA) known as interval 1A on the Y chromosome. There are males who have inherited two X chromosomes, which would normally make them female. However, these individuals have also inherited interval 1A. Therefore, they have descended testes and normal male external genitalia, but they are sterile. A female was discovered whose chromosomes had undergone a reciprocal translocation, a segment of a Y chromosome was interchanged on chromosome 22. However, the Y chromosome had a deletion of a part of the 1A segment, which indicates that this segment is responsible for determination of maleness. The portion of interval 1A was identified in four males who had two X chromosomes. The portion of interval 1A in these four individuals was not the same as observed in the masculinized female. Further study showed that a second deletion occurred in the masculinized female which was the same as in the XX individuals. This segment of DNA may contain more than one genetic element that contributes to the sex-determining function of maleness. The masculinized female that was studied did not have Turner's syndrome, an inherited disease, where females are missing one X chromosome. This subject had the ZFX gene, but not the ZFY gene, genes which are thought to cause Turner's syndrome. Therefore, it was concluded that the ZFX and ZFY genes do not cause Turner's syndrome. (Consumer Summary produced by Reliance Medical Information, Inc.)

Turner syndrome

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What makes a man a man?

Article Abstract:

In 1959, it was shown that the Y chromosome determined if an organism became male. In 1966, the region of the Y chromosome that contained the male determining factor was localized to the short arm of the Y chromosome. Studies with men who had two X chromosomes and only a segment of the Y chromosome allowed the identification of a sequence of deoxyribose nucleic acid (DNA) that is known as the testis-determining sequence. Further analysis allowed localization of the important sequences in that region. These sequences were cloned and the genes were analyzed. The gene coded for a protein, known as a zinc-finger-containing protein, which has a particular shape and is similar to other proteins that bind to DNA and are involved in the regulation of gene expression. However, males were found that did not have this zinc-finger-protein, but did have the sequence of DNA where the zinc-finger-protein was located. This indicated that another gene was responsible for testis determination. A gene called SRY (sex-determining region of the Y chromosome) was found, which has homology with a protein required for mating in yeast and with other identified nuclear proteins that function as transcription factors. Transcription factors bind to DNA and are involved in gene expression. Four other genes have been identified in the mouse, which have a similar DNA sequence as SRY. These genes are expressed in the mouse embryo. Further study will show if SRY is indeed the gene that determines testis formation. (Consumer Summary produced by Reliance Medical Information, Inc.)

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A gene from the human sex-determining region encodes a protein with homology to a conserved DNA-binding motif

Article Abstract:

The inheritance of the Y chromosome determines if an embryo will be male. Genes that determine maleness include those that induce development of the testis and the subsequent sexual differentiation from the production of hormones by the testis. The gene that encodes a factor that determines testis development is known as the testis determining factor (TDF). The location of the TDF gene has been narrowed down to a certain sequence on the Y chromosome. A gene from this region has been identified, and it has been suggested that it may be the TDF. The gene is called SRY (sex-determining region of the Y chromosome), and is similar in many different species of mammals. SRY resembles nuclear proteins that function as transcription factors and is similar to a protein that is required for mating in yeast. Transcription factors bind to deoxyribose nucleic acid (DNA) and are involved in the gene expression. It was shown that this gene is expressed only in tissues of the testis. Further study will show if SRY is indeed the gene that determines the formation of the testis. (Consumer Summary produced by Reliance Medical Information, Inc.)

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