Molecular Basis of Inheritance — BIOLOGY STD 12 Science — Question

Write the mode of pollination in Vallisneria and water lily. Explain the mechanism of pollination in Vallisneria.

Name and explain the surgical method advised to human males and females as a means of birth control. Mention its one advantage and one disadvantage.

Explain in detail about pollen-pistil interaction.

During reproduction, the chromosome number (2n) reduces to half (n) in the gametes and again resume the original number (2n) in the offspring, what are the processes through which these events take place?

Eco RI is used to cut a segment of foreign DNA and that of a vector DNA to form a recombinant DNA. Show with the help of schematic diagrams.

1. The set of palindronic nucleotide sequence of base pairs the Eco RI will recognise in both the DNA segments. Mark the site at which Eco RI will act and cut both the segments.
2. Sticky ends formed on both the segments where the two DNA segments will join later to form a recombinant DNA.

Mention the role of (i) selectable marker, (ii) Ori and (iii) rop in E.coli cloning vector, pBR 322.

Construct an ideal pyramid of energy when 1,000,000 joules of sunlight is available. Label all its trophic levels.

What will be the ploidy of the cells of the nucellus, microspore mother cell, the functional megaspore and female gametophyte?

Match Column I with Column II.

S. No.	Column I	S. No.	Column II
A.	Cleavage	1.	Outer layer of the blastocyst that attaches to the endometrium during implantation.
B.	Implantation	2.	Mitotic divisions of the zygote in quick succession.
C.	Inner cell mass	3.	Embedding of the blastocyst in the endometrium of uterus.
D.	Trophoblast	4.	Release of secondary oocyte from the ovary.
E.		5.	Group of cells attached to one end of trophoblast that differentiate into embryo proper.

Correct the following statements:

1. Surgical methods of contraception prevent gamete formation.
2. All sexually transmitted diseases are completely curable.
3. Oral pills are very popular contraceptives among the rural women.
4. In E. T. techniques, embryos are always transferred into the uterus.