Evolution — BIOLOGY STD 12 Science — Question

Unless the vector and source DNAs are cut, fragments separated and joined, the desired recombinant vector molecules cannot be created.

1. How are the desired DNA sequences cut?
2. Explain the technique used to separate the cut fragments.
3. How are the resultant fragments joined to the vector molecule?

Discuss the process of translation in detail.

a. Describe the process of double fertilisation in angiosperms.
b. Trace the development of polyploidal cell that is formed after double fertilisation in a non-albuminous seed and albuminous seed.

The following diagrams are the age pyramids of different populations. Comment on the status of these populations.

Show that Darwin's natural selection is based on theoretical factual observations, with an example for each.

During the reproductive cycle of a human female, when, where and how does a placenta develop? What is the function of placenta during pregnancy and embryo development?

A. Cryptorchidism is a condition in which the testes fail to descend into the scrotum. It can also lead to compromised Sertoli cell function and has an impact on Leydig cell function.
(i) Identify at least 3 parameters of male fertility which get affected due to cryptorchidism.
(ii) Which process will be affected if mature spermatids are not released from Sertoli cells?
(iii) Name and explain one assisted reproductive technology (ART process) in which the sperm/semen is used to assist fertilization.
(iv) Name and explain the assisted reproductive technology that should be used to complete the development of embryos I and II shown in the figure given below.

Draw and explain a logistic curve for a population of density (N) at time (t) whose intrinsic rate of natural increase is (r) and carrying capacity is (k).

What are the advantages and disadvantages of cross-pollination?

(i) Write the causes of cancer.
(ii) Explain cancer detection.
(iii) Draw a schematic diagram of the lymphatic system.