Question

QUESTION 1

What letter corresponds to the phase in which voltage-gated Na+ channels are open?

action potential.pdf

A.

B.

C.

D.

E.

QUESTION 2

Which of the following statements is true about the mRNA whose structure is depicted in the diagram shown below? mRNA schematic.pdf

A.This could be a primary transcript from a prokaryote.

B. This could be a primary transcript from a eukaryote but not a prokaryote.

C. This could be a mature mRNA from a eukaryote but not a prokaryote.

D. This could be a mature mRNA from either a prokaryote or a eukaryote

E. This could be a primary transcript from either a prokaryote or a eukaryote.

QUESTION 3

Which of the following events are shared between mitosis and meiosis?

A. Homologous chromosomes align

B. Random assortment of homologous chromosomes occur in metaphase of mitosis and metaphase of meiosis II

C. Sister chromatids separate in anaphase of mitosis and anaphase of meiosis II

D. Both mitosis and meiosis have one round of replication and two rounds of cytokinesis

QUESTION 4

Choose the best answer below that describes components of transcription as they are found in prokayotes and eukaryotes.

A. Sigma factor is in both, promoters are in both, and promoters are made of DNA.

B. Sigma factor is only in prokaryotes, promoters are only in prokaryotes, and promoters are made of DNA.

C. Sigma factor is only in prokaryotes, promoters are in both, and promoters are made of DNA.

D. Sigma factor is only in prokaryotes, promoters are in both, and promoters are made of protein.

E. Sigma factor is in both, promoters are in both, and promoters are made of protein.

QUESTION 5

Which of the following always occurs when a ligand binds to its receptor?

A. A signal is transduced.

B. A conformational change occurs in the receptor

C. Second messengers are activated

D. A and C

Answer 1

Q1. The options are not given. The voltage gated Na+ opens when the voltage reaches -55mV ( resting membrane potential is -70mV)  This leads to influx of positively charged sodium ions and leads to rise in potential +30 mV causing depolarisation of the membrane.

Q2.again the question is incomplete and the diagram is not available. I will tell you the characteristic features of mRNA at different stages. Please try to solve it yourself or upload this question with a diagram again.

primary transcript from a prokaryote will not have introns or a 5'cap. The transcription and translation happens in one chamber - cytoplasm and thee is no need for capping.

primary transcrip from eukaryotes will have a poly A tail, 5' cap and introns.
mature mRNA from a eukaryote will retain its 5'cap and polyA tail whereas mature mRNA from prokaryote has no cap.

Q3. In both the cases homologous chromosome align on the metaphase plate. It happens at metaphase stage in mitosis and metaphase II in meiosis.

Q4. The correct answer is C. Sigma factor is found in prokaryotes .transcription factors in eukaryotes are different and numerous.
In both prokaryote an eukaryote the transcription factors binds to promoter and this promoter is a DNA sequence.

Q5. It is not necessary that a signal will be transducer on binding of a ligand to a receptor. It can simply change the conformation of the receptor. Also, activation of second messaged is not compulsory in every ligand receptor interaction. What is compulsory is a change in conformation of the receptor on binding with a ligand. This change is responsible for further actions such as signal transduction and activation of second messenger which may or may not occur. Hence correct answer is B .