Human chorionic gonadotropin (hCG) is known to facilitate attachment of blastocyst to uterus. In women with a mutation in the hCG gene, biologically inactive hCG was formed but implantation occurred. When hCG was immuno-neutralized in the uterus of a normal woman, implantation failed. This suggests that for implantation in humans:
biologically active circulating hCG is not required.
blastocyst can produce the required hCG, which helps locally in uterine attachment.
trophoblastic cells do not require hCG for the invasion of the uterus.
extra-embryonic tissue is not responsible for the attachment of the embryo to the uterus.
B.
blastocyst can produce the required hCG, which helps locally in uterine attachment.
The implantation in humans takes place in the blastocyst. It can produce the required levels of hCG which will help locally in uterine attachment.
If an Arabidopsis plant, mutated in lycopene biosynthetic pathway is grown in a sunny tropical climate in the presence of oxygen:
it would accumulate higher biomass due to higher rate of photosynthesis
there will not be any influence of this mutation on the rate of photosynthesis and plant growth.
it would show reduced biomass due to photo-oxidative damage
the leaves would be bluish-purple in color because of the higher accumulation of xanthophylls.
Segmentation genes in Drosophila are divided into three groups (gap, pair-rule, and segment polarity) based on their mutant phenotype. below are some of their major genes expressed in a sequential manner (with respect to the groups) affecting segmentation pattern.
(A) hairy → paired → tailless → patched hunchback → even-skipped → Fushi tarazu → wingless
(B) hunchback → even-skipped → Fushi tarazu → wingless
(C) odd-skipped → giant → paired → wingless
(D) tailless → hairy → Fushi tarazu → gooseberry
Which of the above sequence(s) of genes expressed from early to late embryo is/ are correct?
(D) only
(A) and (B)
(C) and (B)
(B) and (D)
Which of the inferences (A-D) given below would you draw from the following tissue transplantation experiments performed with the early and late gastrula stages of the newt?
| Host regions | Donor regions | Differentiation of donor tissue | |
| EARLY GASTRULA | |||
| (i) | Prospective neurons | Prospective epidermis | Epidermis |
| (ii) | Prospective epidermis | Prospective neurons | Neurons |
| LATE GASTRULA | |||
| (i) | Prospective neurons | Prospective epidermis | Neurons |
| (ii) | Prospective epidermis | Prospective neurons | Epidermis |
(A) Cells of early newt gastrula exhibit conditional development.
(B) Cells of early newt gastrula exhibit autonomous development.
(C) Cells of late newt gastrula exhibit conditional development.
(D) Cells of late gastrula exhibit autonomous development.
The correct inferences are:
(A) and (D)
(B) and (C)
(A) only
(D) only
During fertilization in mammals, sperm-egg interaction is mediated by zona pellucida (ZP) membrane proteins and their receptors present in the sperm membrane. ZP3 has been identified to be the principle ZP protein whose post-translational modification is important for sperm-egg interaction. In a competitive inhibition assay the sperm is saturated with either active ZP3 or its modified forms, before studying sperm-egg interaction. Which of the following experiments will NOT inhibit sperm-egg interaction?
Saturate sperm with ZP3 protein prior to use.
Deglycosylate the ZP3 protein and use it for saturation of sperm.
Phosphorylate the ZP3 protein and use it for saturation of sperm.
Dephosphorylate the ZP3 protein and use it for saturation of sperm.
Polyspermy results when two or more sperms fertilize an egg. It is usually lethal since it results in blastomeres with different numbers and types of chromosomes. Many species therefore, have two blocks to polyspermy: the fast block and the slow block.
In case of sea urchins:
(A) the fast block is immediate and causes the egg membrane resting potential to rise which does not allow the sperm to fuse with the egg and is mediated by an influx of sodium ions.
(B) the fast block is immediate and causes the egg membrane resting potential to rise which does not allow the sperm to fuse with the egg and is mediated by an efflux of sodium ions.
(C) the slow block or cortical granule reaction is mediated by calcium ions.
(D) the slow block or cortical granule reaction is mediated by potassium ions.
Which of the above statements are true?
(A) and (C)
(A) and (D)
(B) and (C)
(B) and (D)
In an experiment, the cells that would normally become the middle segment of a Drosophila leg were removed from the leg forming area of the larva and were placed in the tip of the fly's antenna. Based on the "French flag" analogy for the operation of a gradient of positional information, which of the following statements is true?
The transplanted cells retain their committed status as leg cells, but respond to the positional information of their environment by becoming leg tip cells-ie., claws.
The transplanted cells are determined as leg cells and therefore would form a complete limb instead of an antenna.
The transplanted cells would intermingle with the cells present in the new environment and develop accordingly to give rise to an antenna.
The transplanted cells retain their committed status as leg cells and would develop to form a chimeric structure having a proximal region made of an antenna and the distal region ending in a complete leg.
Dendritic cells (DC) from BALB/c mice were treated with 1L-10or IFN-γ. Similarly, dendritic cells from β2-microglobulin-deficient mice were also treated with 1L-10 or with IFN-γ. These cells were co-cultured with CD8+ T cells from hen egg lysozyme (HEL)-specific T cell receptor transgenic mice in the presence of the HEL peptide. five days later, CD8+ T cells were assayed for target cell lysis. Which one of the following combinations will have the highest target cytotoxicity?
DC (BALB/c)IL-10 × CD8+T
DC (BALB/c)IFN-γ × CD8+T
DC (β2-microglobulin-deficient)IL-10 × CD8+T
DC (β2-microglobulin-deficient)IFN-γ × CD8+T
During reproductive development in plants:
(A) male and female gametes are produced as a result of two mitotic division after meiosis.
(B) vegetative cell sin pollen contribute to pollen development.
(C) antipodals provide nourishment to developing embryos.
(D) pollen tube ruptures and releases both the male gametes in on of the degenerated synergids.
Which of the above statements are true?
(A) and (B)
(B) and (D)
(B) and (C)
(A) and (D)
According to the current model of alternative oxidase regulation, the following factors cause induction of alternative oxidase:
(A) significant increase in the ubiquitin pool in the cytosol.
(B) presence of α-keto acids (like pyruvate and glyoxylate).
(C) cold stress.
(D) increase in cytosolic ATP concentration.
Which one of the following combinations of above statement is true?
(A) and (D)
(B) and (C)
(A) and (B)
(A) and (C)
