In the chicken ovary cells that surround the growing egg cel

In the chicken ovary, cells that surround the growing egg cell begin to produce high levels of estrogen during oogenesis. Liver cells respond to estrogen by producing large leases vitellogenin into the bloodstream where it will eventually be absorbed by the cells in the ovary and used to create three different yolk proteins to be placed into the developing egg. Explain how this system provides an example of \'epigenetic inheritance\' in roosters Explain how the production of vitellogenin in the liver as described above provides an example of environmental effects in hens.

Solution

Answer- Epigenetic inheritance is a process in which chromosome changes occur without changing genetic sequence in DNA sequence.It occurs due to the switching off and on specific gene .

As we know DNA is a hereditary molecule in all living beings which defines the phenotype by means of genotype.

DNA contain many different genes which are responsible for individual phenotype and function.

Each gene is responsible for specific character.If we compare 2 identical twins,the genetic map we can find almost 99% gene are same in both individual but still they are different phenotypically.

This difference are due to the switching off and switching on gene in both of them. Although both of them contain same gene but due to switching on and switching off of gene some gene express in one individual while some remain switched off and thus they both are different from each other.

These differences occur due to the epigenetics.

Epigenetics occur due to modification in chromosome by DNA methylation and histone modifications.

DNA methylation involves addition of methyl group at specific position of cysteine and adenine.

Histone is a specific protein component of chromatin which serve as spool around which DNA wind. Histone modifications is also the results of methylation.which causes DNA to either stretch out or contract.During transcription Histone protein removed from the contracted DNA and loosen it. This loosen DNA is able to switch off its gene to produce required protein.

As the example given in question chicken female cells around egg produce estrogens because genes code for estrogens are switched on .Liver producing other protein vitellogenine in response to estrogens which is absorbed by cells around egg and produce 3 different protein in to the yolk of developing egg.

For all these protein to produce ,need switching on the gene code for them in egg laying female.

Rooster ( young male chicken) is unable to produce these protein because of the switching off the related genes.

Which is due to the histone modification which does not open /loosen DNA and thus gene to Produce egg specific protein.