Forums Science Assignment Help Biology What happens if there is a mutation in the sex-determining region of the Y?

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    ankita
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    What happens if there is a mutation in the sex-determining region of the Y? Describe in detail the several ways mutations can affect the sex (or apparent sex) of an individual.

    #16127
    ankita
    Member

    Answer:

    The thought of Y-CHROMOSOME as blank in wasteland theory is disproved and it was found that Y-CHROMOSOME has at least 75 genes whereas X-chromosome is considered to have 900-1400genes.

    Y-CHROMOSOME consist(pars) pseudo autosomal regions which are homologous with X-CHROMOSOME for recombination at the time of miosis.

    The region which does not synapse or recombine is called NRY (Non-Combining region of Y-CHROMOSOME and now is called (MRY) (Male -specific region of Y).

    The division of MSY is equally by the euchromatin and heterochromatin that code for functional gone and no gene at all respectively.

    SRY (Sex -determining the region of Y-CHROMOSOME) adjacent to PRA (Pseudo autosomal regions) are the crucial gene which influences the sex of an individual. The TDF (Testis Determining Factor) is protein coded by this (SRY)gene which causes the differentiation of gonadal tissue into Testis.

    TDF act as the main factor and is found that it is DNA binding protein and works as a transcription factor that also helps in the expression of other related genes. The TDF causes the activation of. MIS (Mullerian Inhibiting Substance) which causes the inhibition of the Mullerian ducts all the female reproductive parts.

    Other genes which are activated and initiated by TDF are the cascade of certain genes like SOX9 gene and WTI gene. These genes are present on chromosome 11. Metabolism of steroid hormones are regulated by the expression of another gene called SF1 which is present in both the male and female but after the testes formation is permanent, this gene exp become lost in females but remain in males.

    The male-specific region (MSY) consists of three regions and these are:

    i) X – transported region
    ii) X – degenerative region
    iii) Amplicon region

    i) X – transported region – It’s most of the region almost about 99% is same as the X – chromosome of human and identical to Xq21 region.

    ii) X- degenerative region – Containing 27 single copy genes it also contains pseudogenes (non – functional) genes. Genes on this region have homologous regions on X – chromosome in which 14 of them are capable of transcription and SRY gene is one of this gene but it’s expression limited only to the testis formation while the other have their effect on all the other parts of the body.

    iii) Amplicon region – This covers about 80% of the region of the Y- chromosome and all affect testis development, lacking their homologous sequences on X chromosome, have 60 transcription units which are present in multiple copies divided in a 9-gene family. They have sequences called palindromes which help in the occurrence of mutation in the Y – chromosome by recombination between sister chromatids.

    So, the mutation in all these genes the Y – chromosome can lead to the sterility and infertility and other diseases. One of the disease due to a mutation in SRY gene is the campomelic dysplasia in which the sex of the diseases remains undetermined and there is the presence of external genitalia.

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