131.

According to fossil records, the earliest fossils of liverworts are found in the late Devonian, of mosses in the early Cretaceous, and vascular plants in the last Silurian/ early Devonian. Anthoceros (hornworts) fossils have not been discovered. Reading fossil records we would say that vascular plants appeared first, then mosses and then liverworts.

  

However, phylogenetic relationships (shown in the figure) suggest otherwise. It may be that:

(A) evolutionary history can be read directly from the fossil record.

(B) the moss lineage goes back to at least early Silurian/ early Devonian.

(C) fossils can only set a maximum age for a lineage.

(D) fossils can only set a minimum age for a lineage.

(E) the divergence between liverworts and the rest of land plants goes back to at least the early Ordovician.

Which of the following statements is correct?

• (A), (B), (C), (E)

• (B), (D), (E)  

• (A), (B), (D), (E)

• (B), (C), (E)

Northern Elephant seals had been reduced to about 20 individuals in the 1800s. Biologists studied variation in proteins in the species. They found no genetic differences in the protein among different individuals. This lack of variation is due to:

• The fact that elephant seals live in a constant environment where there is no need for genetic variation.

• Population bottleneck and genetic drift.   

• Natural selection resulting in a single best genotype.

• A very low rate of mutation

There are ‘n’ number of alleles for a given locus in a diploid population. The proportion of all homozygotes in the population (i) if all alleles are equally abundant and (ii) if all alleles are not equally abundant, will be:

• (i) 1/ n   (ii) < 1/ n

• (i) 1/ n  (ii) > 1/ n   

• (i) 1/ n²   (ii) < 1/ n²

• (i) 1/ n²   (ii) > 1/ n²

Which of the following is a prediction of the neutral theory of molecular evolution that is supported by data?

• Humans and chimps differ more in DNA sequences of pseudogenes than in coding regions of functional genes.  

• Humans and chimps differ more in DNA sequences of coding regions of functional genes than of pseudogenes.

• Humans have a faster evolution of most of their DNA sequences than chimps.

• The more advanced species have more number of functional genes.

In hymenopteran insects, males are haploid and females are diploid. All fertilized eggs give rise to females and unfertilized eggs give rise to males. As a result, if a female mates with a single male, the females in the progeny are related to each other by 75%. But if the mother had mated with many males, the mean genetic relatedness of female progeny is correctly represented by:

In a Radio-immunoassay (RIA) for glucocorticoid hormone, radioactive glucocorticoid (tritiated) is added to the RIA cocktail. When the amount of bound hormone was measured no counts were observed. The following explanation (s) were proposed:

A. The radioactive hormone was insufficient.

B. The radioactive tag to the hormone completely dissociated during storage.

C. The antibody was not added to the cocktail.

D. The specific activity of the tritium was low.

Choose the correct option (s):

• (A) only

• (C) only

• (B) and (C)

• (A) and (D)

Which of the following curves correctly represents the process of antibiotics production by Streptomyces species.

For the generation of transgenic plants in crop improvement, one important gene X was expressed in a crop plant. Out of 30 transgenic rice plants generated, 22 showed high levels of gene X expression. However, rest 8 lines displayed low levels of expression. One explanation of such observation may be:

• suppression effect of the transgenic

• knock-down effect of the gene X.

• gene silencing effect

• co-suppression effect of the transgene

Ten different mouse strains were primed with whole Keyhole limpet hemocyanin (KLH). KLH was broken into ten peptides for in vivo stimulation. The splenocytes from ten different primed mouse strains were restimulated with each of these ten peptides and the responsiveness to these peptides. When the peptide 3 responder was mated with peptide 4 responder, the splenocytes of F₁ offspring responded to both the peptides. Which of the following is most appropriate?

• Mouse strains responding to peptide 3 or peptide 4 have different MHC haplotypes.

• Mouse strains responding to peptide 3 or peptide 4 have either of these T cell receptors.

• Mouse strains responding to peptide 3 or peptide 4 cannot process KLH.

• Mouse strains responding to peptide 3 or peptide 4 did not express MHC class-I molecule.

Stem cells are widely used for their regenerative property and capacity to differentiate into different lineages. A person with a damaged liver approaches a stem cell therapist. Which of the following therapeutic strategies would be the safest?

• procuring adult liver cells from a healthy donor and grafting them into the patient.

• transforming skin cells from the patient into iPS cells and using them for further differentiation and grafting in the liver.

• injecting embryonic stem cells into the damaged liver.

• injecting cord blood cells into the liver directly