Which one of the following changes will occur in the cell membrane of nodal tissue of heart, which results in an increased heart rate due to the stimulation of sympathetic nerves?

• Opening of sodium channels is facilitated.

• Potassium conductance is increased.

• Opening of L-calcium channels are facilitated.   

• ‘h’ channels are inhibited.

The respiratory chain is relatively inaccessible to experimental manipulation in intact mitochondria. Upon disrupting mitochondria with ultrasound, however, it is possible to isolate functional submitochondrial particles, which consists of broken cristae that have resealed inside out into small closed vesicles. In these vesicles the components that originally faced the matrix are now exposed to the surrounding medium. This arrangement helps n studying of electron transport and ATP synthesis because:

• It is difficult to manipulate the concentration of small molecules (NADH, ATP, ADP, Pi) in the matrix of intact mitochondria.     

• In broken cristae, the enzymes and other molecules responsible for electron transport aremore active.

• Intact mitochondria are more unstable than broken cristae.     

• Purification of intact mitochondria is not possible.

The lac operon in E.coli, is controlled by both the lac repressor and the catabolite activation protein CAP. In an in vivo experiment with lac operon, the following observations were made:

(A) cAMP levels are high         

(B) Repressor in bound with allolactose.

(C) CAP is interacting with RNA polymerase.

Which one of the following conclusions is most appropriate based on the above observations?

• Glucose and lactose are present.

• Glucose is present and lactose is absent.      

• Both are absent.

• Glucose is absent and lactose is present.  

The pattern of embryonic specific to a species is determined by two major parameters.

(A) The amount and distribution of yolk protein within the cytoplasm.

(B) The factors in the egg cytoplasm that influence the angle of mitotic spindles and the timing of its formation.

Which of the following statements is true?   

• Species having telcolecithal egg follow a holoblastic cleavage.

• Species having isolecithal follow a holoblastic cleavage.    

• Species having centrolecithal eggs follow a holoblastic cleavage.      

• Species having isolecithal egg follow a meroblastic cleavage.

35.

The fate of a cell or a tissue “specified” when it is capable of differentiating autonomously on being placed in a neutral environment with respect to the developmental pathway. An embryo will show a developmental pattern based on its type of specification:

Based on the above facts it can be said that the potency of a cell is:

(A) equal to its normal fate in regulative development.                 

(B) greater than its normal fate in regulative development.

(C) equal to its normal fate in mosaic development.

(D) greater than its normal fate in mosaic development.

Which of the above statements are true?

• (B) and (C)   

• (A) and (D)

• (A) and (C)

• (B) and (D)

The stereocilia of auditory hair cells are arranged in rows but the heights of stereocilia are not the same in all rows. Though the height of stereocilia is the same within a particular row, the heights increase in subsequent rows. When the stereocilia of shorter rows are mechanically pushed towards the taller rows, the hair cells are depolarized but a push on opposite direction hyperpolarizes them. The significance of this graded height of stereocilia is:

(A) Each row of sterecilia may be displaced independently of other rows in physiological conditions.

(B) The tip of the taller stereocilia will show greater displacement as compared to shorter ones when all the rows are moving in the same axis.

(C) The hair cells will be depolarized or hyperpolarized in different grades when the axis of displacement is changed.

(D) The taller stereocilia are involved with depolarization and shorter ones are responsible for hyperpolarization.

Which one of the following is correct?

• (A) only

• (B) only

• (B) and (C)  

• (A) and (D)

Which of the following statements regarding aquaporins or water channel is NOT correct?           

• Aquaporins are found in both plant and animal membranes.

• Aquaporins cannot transport unchanged molecules like NH₃.    

• Phosphorylation and calcium concentration regulate aquaporin activity.

• The activity of aquaporin is regulated by pH and reactive oxygen species.

A cell undergoing meiosis produces four daughter cells, two of which are aneuploids, while two are haploid. This can occur due to:

• Non-disjunction during the first meiotic division only.

• Non-disjunction during the second meiotic division only.

• Non-disjunction during either first or second meiotic division.

• Non-disjunction during both first and second meiotic division.

Identify a, b and c in the figure:

• a – mitochondria; b – multicellularity; c – chloroplast

• a – mitochondria; b – chloroplast; c – multicellularity

• a – chloroplast; b – multicellularity; c – mitochondria

• a – chloroplast; b – multicellularity; c – mitochondria

The rates of mutation in E.coli from lac are determined using a medium containing lactose, as the only source of energy. The principle of spontaneity of mutations can be said to be violated if:

• The rate of mutation increases during starvation.

• In the presence of lactose, the rate of mutation from lac^- to lac⁺ is increased but the overall rate of mutation is not.   

• The rate of mutation in the lac gene is always greater than that in other genes.

• The rate of mutation in the lac gene is always then that in other genes.