Which of the following is primarily responsible for the maternal effect? A. Sper

Question

Which of the following is primarily responsible for the maternal effect?

A. Sperm cells

B. Nurse cells

            C. Placenta

Mendel’s work with single-factor crosses resulted in the development of which of the following?

            A. Law of Segregation

            B. Theory of natural selection

            C. Law of biological evolution

            D. All of the answers

Expression of _ would inhibit X-inactivation.

            A. Xic

            B. Xist

            C. All of the answers

            D. None of the answers

Explanation / Answer

* Maternal effect is the process in which the phenotype of an organism is determined by the environment and genotype of its mother also, apart from other factors. In drosophila, oocyte develops in an egg chamber along with a set of cells called nurse cells which have an incomplete cytokinesis. Some of the genes like bicoid, dorsal, gurken are expressed in nurse cells and not in oocyte. The correct answer is B. Nurse cells.

* Mendel's work with single-factor crosses resulted in "Law of segregation." The correct answer is option A. He worked with purebred white flower pea plants and purple flower pea plants the crossing of which resulted in a purple flowered plants and the result was not a blend of the colours. From his observations of single-factor crosses, he developed the theory of law of segregation.

* X-inactivation center (Xic) on the X chromosome controls the silencing of X chromosome. X-inactive specific trnascript (Xist) acts as an effector of the X inactivation process. Both these components are involved in X-inactivation. Hence, the correct answer is option D. None of the answers.

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