Question

Is everyone's paternal gene silenced because of imprinting in that section of chromosome 15 that causes angelman syndrome? (when the other parents gene is silenced and now there is no back up because of imprinting caused by methylation) I'm asking if every typical person has this imprinting for angelman syndrome and vice versa maternally for Prader-willie syndrome I'm getting confused while writing a report.
(I need help as soon as possible because I'm writing a report for tomorrow). Thank you! I give thumbs up.

Answer 1

To answer your first of all lets understand what is genomic imprinting

When an embryo is formed by fusion of male and female nucleus than all the genes from sperm nucleus and egg nucleus is not functionally equivalent.Some of gene of maternal side and some of paternal side are activated other genes are inactivated or silenced by methylation in cytosine residue ofDNA so basically genomic imprinting is Inactivation of gene

In everyone pair of chromosome present in which half chromosome comes from paternal father side and half chromosome comes from mother maternal side.so basically every child has two copy of single gene but not both copy are functional one copy either from paternal side or maternal side is Inactivated by methylation in cytosine residue as we have discussed above its called genomic imprinting

Hence for Normal development of embryo single copy of every gene is normal and other is inactivated or silenced

Now coming to the question Prader wili and angelmon syndrome is caused due to some deletion or mutation in the region of chromosome 15

As you know due to genomic imprinting some gene of chromosome15 of paternal side will be activated and other will inactivated silenced in the same way some gene of maternal side chromosome 15 will be activated and other inactivated or silenced

Genes of maternal side which is activated is silenced in paternal side and vice-versa for maternal side hence only one copy of single funtional gene is present

In chromosome 15 some gene are activated from paternal side and maternal side gene are inactivated silenced by imprinting but when there is deletion or mutation on region of paternal side chromosome 15 than genes of that area will not be expressed and causes Prader willi syndrome in which child has small stature ,small hand and feet and is mentally retarded.

In the same way some genes is activated on maternal side chromosome 15 and paternal side genes on chromosome 15 is inactivated silenced so if there is deletion or mutation of that specific genes on maternal side chromosome 15 than it will cause Angelman syndrome in which there is uncontrolled muscle movement, feeding issues and frequent laughter ( Always smile).

In both cases other copy of paternal or maternal side chromosome is normal but as it is turned off by imprinting so it cannot fill the gaps hence the presence of a second good copy of the gene on the methylated, tightly packed copy of chromosome 15 is of no use in correcting the defect.

So your query that everyone's paternal gene silenced because of imprinting in that section of chromosome 15 that causes angelman syndrome and vice-versa for prader-willi syndrome

Yes it is true In prader willi syndrome and angelman syndrome one copy of gene of paternal side or maternal side is defected but other copy of maternal side or paternal is Normal but they are silenced due to imprinting that is methylation on cytosine residue of DNA and it cannot be activated

Hence In every person that paternal gene section of chromosome 15 that causes angelman syndrome is silenced due to imprinting and vice-versa for prader-willi syndrome

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