46. Baldness of male is due to-
(1) X- linked (2) Y-linked
(3) Autosomal (4) Multifactorial
Male baldness, particularly male pattern baldness (androgenetic alopecia), is best described as a multifactorial trait influenced by multiple genes, including a key gene located on the X chromosome, making option (4) Multifactorial the most accurate. This means that while the androgen receptor (AR) gene on the X chromosome plays a significant role, genes on autosomes and other factors also contribute to baldness.
Explanation of Each Option
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X-linked: Male pattern baldness is strongly associated with the AR gene on the X chromosome, inherited from the mother. However, baldness is not solely determined by this gene, so it is not purely X-linked.
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Y-linked: Baldness is not linked to the Y chromosome; no major baldness genes have been identified on the Y chromosome.
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Autosomal: Several autosomal genes contribute to baldness risk, affecting hair follicle biology and hormone metabolism, but baldness is not exclusively autosomal.
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Multifactorial: Baldness arises from the combined effects of many genes (including both X-linked and autosomal), as well as environmental factors and hormonal influences such as sensitivity to dihydrotestosterone (DHT). This broad inheritance pattern makes baldness a multifactorial trait.
Introduction:
Male baldness, or androgenetic alopecia, is a common form of hair loss influenced by multiple genetic and environmental factors. Although a key gene on the X chromosome, the androgen receptor (AR), significantly contributes to baldness risk, genes on autosomes and hormonal effects play crucial roles. This multifactorial inheritance pattern explains why baldness cannot be traced to a single cause or chromosome alone.
Detailed Explanation
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X-linked Role: The AR gene on the X chromosome influences hair follicle sensitivity to hormones like DHT, which leads to hair follicle shrinkage and baldness. Men inherit their X chromosome from their mother, explaining patterns of inheritance through maternal lineage.
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Autosomal Contribution: Numerous autosomal genes regulate hair follicle development, hormone metabolism, and immune responses affecting baldness susceptibility. These genes act in combination with the X-linked gene.
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Why Not Y-linked: No evidence supports major baldness genes on the Y chromosome, and hair loss is not transmitted via paternal Y chromosome inheritance.
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Multifactorial Nature: Baldness results from gene-gene and gene-environment interactions, hormone sensitivity, and other biological pathways. This complexity is why baldness shows variable onset and severity even within families.
This comprehensive view aligns with genetic studies showing baldness has strong heritability from both X chromosome and autosomal gene variants, classifying androgenetic alopecia as a multifactorial genetic condition.
Hence, the correct answer is (4) Multifactorial.
