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51.

Which of the following is wrong about diplotene?(a) Endoplasmic vesicles increase in the number(b) Nucleolus condenses(c) Chromatid body is seen(d) Chromosomes rotate by 180 degree to terminalizeThis question was posed to me by my school teacher while I was bunking the class.Query is from Meiosis Prophase 1 : Diplotene and Diakinesis topic in division Chromosomal Changes During Meiosis of Cytogenetics

Answer»

The CORRECT OPTION is (b) Nucleolus condenses

Explanation: The nucleolus disintegrates rather than condensing. It is on the WAY of disappearance of nucleolus. However, the other options are TRUE.

52.

What is the stretch of DNA remaining unreplicated during pachytene?(a) 200bp(b) 1000bp(c) 104bp(d) 10 kbThis question was addressed to me in my homework.Question is from Meiosis Prophase 1 : Pachytene in division Chromosomal Changes During Meiosis of Cytogenetics

Answer» RIGHT OPTION is (a) 200bp

Best explanation: In pachytene stage short stretches of DNA remains unreplicated. This is as short as 200bp. In ZYGOTENE stage the unreplicated chromosomes are about 104 bp.
53.

In an experiment you introduce a pair of unpaired homologous chromosomes into pachytene stage, what will you expect to observe?(a) Pairing and subsequent recombination(b) Pairing will occur but no recombination(c) No pairing will occur but recombination will take place(d) Neither pairing nor recombinationI have been asked this question in an internship interview.I would like to ask this question from Meiosis Prophase 1 : Pachytene topic in chapter Chromosomal Changes During Meiosis of Cytogenetics

Answer»

The CORRECT choice is (d) Neither pairing nor RECOMBINATION

Easiest explanation: There is no ADDITIONAL pairing or synaptonemal complex formation at the pachytene stage. Thus, the introduced chromosomes will neither pair, and in ABSENCE of it no recombination will OCCUR.

54.

The fibers of the lateral filament are called____________(a) Synaptomes(b) Synaptomere(c) Synaptic clefts(d) SynaptososomeI have been asked this question during an internship interview.My question is from Meiosis Prophase 1 : Synaptonemal Complex topic in division Chromosomal Changes During Meiosis of Cytogenetics

Answer»

Right answer is (b) SYNAPTOMERE

The explanation: The lateral filament of synaptonemal complex consists of FIBERS called synaptomere. It is SLIGHTLY WIDER than 10 NM.

55.

Nuclear envelope breaks down finally in _____________(a) Prophase(b) Pro metaphase(c) Metaphase(d) AnaphaseThis question was posed to me during an online interview.This is a very interesting question from Meiosis 1 Metaphase, Anaphase & Telophase topic in section Chromosomal Changes During Meiosis of Cytogenetics

Answer»

Right CHOICE is (B) Pro metaphase

Best explanation: In the prometaphase the chromosome compaction reaches its maximum, recombination is COMPLETE, now the nuclear ENVELOPE breaks down and spindle fiber attaches to CHROMOSOMES.

56.

What is the normal number of chiasma seen in diplotene chromosomes?(a) 2(b) 4(c) 8(d) 16The question was asked in an online interview.My question is based upon Meiosis Prophase 1 : Diplotene and Diakinesis in section Chromosomal Changes During Meiosis of Cytogenetics

Answer»

The CORRECT option is (b) 4

Explanation: The number of chiasmata is VARIABLE ALTHOUGH it is usually 4, MAXIMUM number of chiasma may be 13-14. While some cells may have 1 chiasma other may have many more, 4 being the average.

57.

If the pairing starts at terminal and proceeds towards centre it is known as ________________(a) Procentric(b) Proterminal(c) Random(d) AcrocentricI have been asked this question in an online interview.The query is from Meiosis Prophase 1 : Zygotene topic in portion Chromosomal Changes During Meiosis of Cytogenetics

Answer»

The correct answer is (b) Proterminal

The explanation: In pro-terminal LENGTHWISE pairing the pairing BEGINS at the terminal and then it proceeds towards the CENTRE. The reverse CASE is known as procentric.

58.

What is the bivalent shape in diakinesis?(a) X shaped(b) O shaped(c) Y shaped(d) Star shapedI had been asked this question in an interview.My question is from Meiosis Prophase 1 : Diplotene and Diakinesis in division Chromosomal Changes During Meiosis of Cytogenetics

Answer»

Right choice is (b) O SHAPED

Easiest explanation: The chromosome in diakynesis STAGE is O shaped as it is only connected in the TERMINAL end and rest of the parts REPEL. The chromosome is also in its most condensed stage in this phase.

59.

The pairing of the chromosome is mediated by _______________ interactions.(a) Hydrophilic(b) Hydrophobic(c) Covalent(d) ElectrostaticI got this question during an interview.This intriguing question comes from Meiosis Prophase 1 : Synaptonemal Complex topic in portion Chromosomal Changes During Meiosis of Cytogenetics

Answer» CORRECT OPTION is (d) ELECTROSTATIC

The best I can explain: The tails of TWO opposite zygosomes are oppositely charged. This brings about pairing by electrostatic interaction.
60.

The formation of synaptonemal complex is ______________ DNA replication in zygotene.(a) Before(b) Simultaneous(c) After(d) Unrelated toI got this question in quiz.My question is from Meiosis Prophase 1 : Zygotene topic in chapter Chromosomal Changes During Meiosis of Cytogenetics

Answer»

The correct choice is (c) After

The best I can EXPLAIN: The replication of DNA in ZYGOTENE is mandatory for a synaptonemal complex formation to OCCUR. These regions are ALSO the first to get paired.

61.

Pairing of chromosome is initiated by hydrodynamic force.(a) True(b) FalseI have been asked this question during an interview for a job.My query is from Meiosis Prophase 1 : Zygotene in chapter Chromosomal Changes During Meiosis of Cytogenetics

Answer» CORRECT option is (a) True

To EXPLAIN I would say: Due to vibrations in the CYTOSOL the CHROMOSOMES PAIR. This pairing is mainly due to hydrodynatic force. Another theory for pairing is via electrostatic force.
62.

Which of the following is true?(a) Zygotene is the phase preceding diplotene(b) DNA replicated in zygotene is incorporated in chromosome 5-6 days later(c) Synaptonemal complex formed is longer than the physical length of chromosomes itself(d) The pairing of chromosomes forces the DNA to replicateThis question was posed to me in an international level competition.Origin of the question is Meiosis Prophase 1 : Zygotene topic in portion Chromosomal Changes During Meiosis of Cytogenetics

Answer»

The correct OPTION is (b) DNA replicated in zygotene is incorporated in chromosome 5-6 days later

The explanation is: DNA replicated in zygotene phase is not immediately incorporated in the chromosome but it takes 5-6 days. While zygotene is followed by pachytene and the synaptonemal COMPLEX is shorter than the chromosome itself. The PAIRING FOLLOWS replication and not vice VERSA.

63.

The point where the synaptonemal complex is attached to nuclear envelope is called _______________(a) Bouque stick(b) Meiotic point(c) Fixation point(d) TelomerinI had been asked this question in exam.The query is from Meiosis Prophase 1 : Pachytene topic in chapter Chromosomal Changes During Meiosis of Cytogenetics

Answer»

The correct CHOICE is (c) Fixation point

Best explanation: The alignment of the homologous CHROMOSOMES is made easier by the fact that the telomeres of the chromosome are frequently attached to the nuclear envelope. At these points of ATTACHMENT, the SCs are LINKED by an electron dense thickening CALLED the fixation plate.

64.

Chromosomal compaction is brought about by________(a) Cohesin(b) Thrombin(c) Condensin(d) SequrinThis question was posed to me in exam.The doubt is from Mitosis Stages Overview in division Chromosomal Changes During Meiosis of Cytogenetics

Answer»

The CORRECT choice is (c) Condensin

Explanation: The condensing MOLECULE has two parts where each BIND to two coils of a chromosome and bring them close. This results in chromosome compaction. Cohesin brings two chromosomes TOGETHER during SYNAPSIS.

65.

What is a negative regulator of Cdc-20?(a) M-Cdk(b) Mad-2(c) Mdm(d) Hct1This question was posed to me during a job interview.My doubt stems from Overview of Cell Reproduction in chapter Chromosomal Changes During Meiosis of Cytogenetics

Answer»

Correct ANSWER is (b) Mad-2

The BEST explanation: Mad 2 bind to unbound KINETOCHORES, which leads to inactivation of Cdc-20. This is a checkpoint that makes sure anaphase only occurs when all the centromeres are bound to spindle. M-Cdk and HCT1 promote activity, while Mdm is not directly LINKED to its activity.

66.

Which of the following is an activation process?(a) Wee1 kinase(b) APC(c) Cdc25(d) p27 bindingThe question was posed to me during an interview.I want to ask this question from Overview of Cell Reproduction topic in portion Chromosomal Changes During Meiosis of Cytogenetics

Answer»

Right option is (c) Cdc25

Best explanation: Cdc25 is a phosphatase that REMOVES the INHIBITORY phosphate of the Cyclin-Cdk that PREVENTS its activity- Thus, it ACTIVATES Cyclin-Cdk. Other processes are inhibitory.

67.

Eggs in female stay in ______________ phase for extended duration.(a) S(b) G1(c) G2(d) MThis question was addressed to me in final exam.Enquiry is from Overview of Cell Reproduction topic in chapter Chromosomal Changes During Meiosis of Cytogenetics

Answer» RIGHT answer is (d) M

For explanation I would say: Eggs are stored for long in the ovary in the diplotene STAGE of meiosis 1 KNOWN as dichtyotene. Then the chromosomes are paired ACCORDING to the homologous pairing.
68.

In haploid organism meiosis takes place in _____________(a) Somatic cell(b) Zygote(c) Gamete(d) EggI had been asked this question in class test.My question is from Meiosis Prophase 1 : Leptotene in portion Chromosomal Changes During Meiosis of Cytogenetics

Answer» RIGHT option is (B) Zygote

Easy explanation: In haploid organisms the zygote is DIPLOID which undergoes meiosis to give a haploid individual. Here, egg and other GAMETE are haploid as is somatic cell, so no meiosis is required by it.
69.

Is it true that a cell can keep on replicating forever?(a) True(b) FalseI have been asked this question at a job interview.I need to ask this question from Mitosis Stages Overview topic in division Chromosomal Changes During Meiosis of Cytogenetics

Answer»

Right choice is (b) False

Best explanation: A REPLICATING cell, ESPECIALLY a somatic cell, has a limit called Hayflick’s limit. This is due to the shortening of the TELOMERE with EVERY cycle of replication that ultimately results in stopping of the replication when telomere is too SHORT.

70.

We know that caffeine helps to overcome M-Cdk activation checkpoint. What will be the fate of the cell treated with hydroxyl urea and caffeine in G1 phase?(a) Cell will not divide(b) Cell will become smaller in size(c) Cell will divide with improper chromosome number(d) Cell will undergo lysisI have been asked this question in an international level competition.The above asked question is from Overview of Cell Reproduction in division Chromosomal Changes During Meiosis of Cytogenetics

Answer»

Right OPTION is (c) CELL will divide with improper chromosome number

Easy EXPLANATION: Hydroxyurea prevents DNA replication. When this is coupled with CAFFEINE that helps overcome M-Cdk CHECKPOINT it leads to improper chromosome distribution among the daughter cells.

71.

In an experiment you increase the concentration of Cln3. What will be its effect on proliferating yeast cells?(a) Cells will be smaller in size(b) Cells will still have normal size(c) Cells will increase in size(d) Cells will die offI had been asked this question in class test.This question is from Overview of Cell Reproduction topic in chapter Chromosomal Changes During Meiosis of Cytogenetics

Answer»

Right option is (a) Cells will be smaller in SIZE

For explanation I WOULD say: Cln3 in yeast INDUCES REPLICATION. If replication is more than cell growth, it will lead to gradual decrease in cell size.

72.

Which of the following will prevent cell cycle from progressing in case of DNA damage?(a) P53(b) G1 cyclin(c) P10(d) Bcl-2I have been asked this question during a job interview.I'd like to ask this question from Overview of Cell Reproduction topic in portion Chromosomal Changes During Meiosis of Cytogenetics

Answer»

The correct option is (a) P53

To elaborate: In case of DNA DAMAGE P53 SENSES the damage in DNA and blocks the further progression of the cell cycle UNLESS the damage is repaired. This can EVEN lead to apoptosis if the damage stays as it is.

73.

If a permanent cell re enters cell cycle it is ______________(a) Differenciation(b) Redifferenciation(c) Dedifferenciation(d) ApoptosisI have been asked this question in exam.The doubt is from Mitosis Stages Overview topic in portion Chromosomal Changes During Meiosis of Cytogenetics

Answer»

The CORRECT answer is (C) DEDIFFERENCIATION

The explanation: While differenciation is the process by which a mitotic CELL becomes permanent, dedifferenciation is the REVERSE. On the other hand re-differenciation is the differenciation of the de-diffenenciated cell.

74.

In cells the DNA replication takes place in _____________ phase.(a) G0(b) G1(c) S(d) G2I have been asked this question in unit test.The origin of the question is Overview of Cell Reproduction topic in division Chromosomal Changes During Meiosis of Cytogenetics

Answer»

The CORRECT option is (c) S

To explain I would say: In CELLS the DNA is replicated in the S phase. In G1 and G2 phase mainly the proteins REQUIRED for mitosis is INCREASED in QUANTITY.

75.

The concentration of which of the following varies during the cell cycle?(a) Cdk(b) Cyclin(c) SCF(d) ProteosomeThis question was posed to me in a job interview.The doubt is from Overview of Cell Reproduction topic in portion Chromosomal Changes During Meiosis of Cytogenetics

Answer»

The correct option is (b) CYCLIN

Explanation: The concentration of cyclin changes in a cyclic way during the CELL CYCLE leading to various events; this regulates the phosphorylation and ACTIVATION of the remaining PARTICIPANTS bringing about cell cycle.

76.

The cells before permanently differentiating enters into ______________ phase.(a) G1(b) G2(c) G0(d) SThe question was posed to me in a national level competition.I want to ask this question from Overview of Cell Reproduction in section Chromosomal Changes During Meiosis of Cytogenetics

Answer»

The correct answer is (c) G0

To elaborate: Before PERMANENT differentiation the CELLS enter into G0 PHASE where they don’t continue with the CELL cycle. This immediately follows G1 phase.

77.

Cdc20___________________ anaphase.(a) Promotes(b) Prevents(c) Slows(d) Unrelated toThe question was posed to me in examination.My enquiry is from Mitosis Stages Overview topic in chapter Chromosomal Changes During Meiosis of Cytogenetics

Answer»

Correct option is (a) Promotes

The best explanation: CDC20 is a cell cycle component that promotes anaphase by DECREASING the M-Cdk level and ALSO LEADING to breakdown to cohesion.

78.

Which of the following true about Rb in the cell cycle?(a) Phosphorylation of Rb will lead to its inactivation(b) Phosphorylation of Rb will also lead to inactivation of E2F(c) Phosphorylation of E2F will promote cell cycle progression(d) E2F is directly affected by RbThe question was posed to me by my school principal while I was bunking the class.This is a very interesting question from Overview of Cell Reproduction topic in chapter Chromosomal Changes During Meiosis of Cytogenetics

Answer»

Right choice is (B) Phosphorylation of Rb will also LEAD to inactivation of E2F

The explanation is: Rb BINDS E2F and prevents cell CYCLE PROGRESSION. If Rb is phosphorylated it will lead to release of E2F leading to continuation of the cell cycle.

79.

Meiosis is called reduction division.(a) True(b) FalseI have been asked this question during a job interview.The query is from Meiosis Prophase 1 : Leptotene topic in division Chromosomal Changes During Meiosis of Cytogenetics

Answer»

The correct choice is (a) True

For EXPLANATION: In meiosis there is a reduction in chromosome number to half that is PRESENT in normal CELL. THUS, meiosis is called reduction division.

80.

_________________ follows __________________(a) Karyokinesis, mitosis(b) Cytokinesis, Karyokinesis(c) Mitosis, Karyokinesis(d) Karyokinesis, CytokinesisI had been asked this question by my college director while I was bunking the class.The question is from Mitosis Stages Overview topic in section Chromosomal Changes During Meiosis of Cytogenetics

Answer»

The correct choice is (B) CYTOKINESIS, Karyokinesis

The best I can explain: Karyokinesis is the DIFFUSION of the nuclear materials which takes place before the cytoplasmic SEPARATION. Thus, cytokinesis follows karyokinesis.

81.

If you use colchicines, which of the cell division phases is prevented?(a) DNA replication(b) Prophase(c) Anaphase(d) TelophaseI got this question in an interview for internship.I want to ask this question from Mitosis Stages Overview in section Chromosomal Changes During Meiosis of Cytogenetics

Answer» CORRECT choice is (c) Anaphase

Easy explanation: Colchicine disrupts the microtubule structure which leads to the ABSENCE of anaphase. While DNA replication is not prevented, so colchicines can EFFECTIVELY lead to chromosomal DOUBLING.
82.

Anaphase is brought about by the change in which cytoskeletal element?(a) Tubulin(b) Actin(c) Myosin(d) DyaninThe question was asked during a job interview.The query is from Mitosis Stages Overview in portion Chromosomal Changes During Meiosis of Cytogenetics

Answer»

The correct answer is (a) TUBULIN

The best EXPLANATION: Tubulin is the subunit of the microtubules that form the SPINDLE FIBRES that help separate the chromatids.

83.

The inactivation of M-Cdk is through the Cdc20-APC activity, what activates Cdc-20-APC?(a) G1-Cdk(b) G1-S-Cdk(c) S-Cdk(d) M-CdkThe question was asked in final exam.This intriguing question comes from Overview of Cell Reproduction in chapter Chromosomal Changes During Meiosis of Cytogenetics

Answer»

Right answer is (d) M-Cdk

To elaborate: M-Cdk itself promotes the ubiquitine lygase that MARKS M-cyclin for DESTRUCTION, THEREBY inactivating M-Cdk. This HELPS in ANAPHASE.

84.

P53 requires ________________for its activity.(a) Mdm(b) MCM(c) Securin(d) CdtThis question was addressed to me during an interview.I would like to ask this question from Overview of Cell Reproduction in section Chromosomal Changes During Meiosis of Cytogenetics

Answer»

Right choice is (a) MDM

The best explanation: P53 prevents cell cycle progression during DNA damage. This is mediated with the help of Mdm which helps it to INDUCE transcription of P21 that helps prevent a CONTINUATION of cell cycle.

85.

Which of the following doesn’t take place in prophase if mitotic cell?(a) Chromosome starts to contract(b) The nuclear membrane breaks down(c) The nucleolus disappears(d) The chromosomes pair up with their homologueThe question was asked in a job interview.My question is from Mitosis Stages Overview topic in division Chromosomal Changes During Meiosis of Cytogenetics

Answer» RIGHT answer is (d) The chromosomes pair up with their homologue

To elaborate: Chromosomal PAIRING is a CHARACTERISTIC of meiotic cell not MITOTIC cell. Most of the steps in PROPHASE of meiosis and mitosis being the same we observe the rest of the steps in mitotic prophase.
86.

If your chromosome is submetacentric, what will be the anaphase shape while separation?(a) I(b) J(c) L(d) VThis question was posed to me during an internship interview.Question is from Mitosis Stages Overview topic in chapter Chromosomal Changes During Meiosis of Cytogenetics

Answer» CORRECT option is (c) L

The best I can explain: During anaphase separation the chromatins are under a FORCE, they tend to formL SHAPED structure if they are metacentraic. I, J and V STRUCTURES are formed by telocentric, acrocentric and metacentric CHROMOSOMES respectively.
87.

Which one of the following doesn’t help in degrading cohesion?(a) Cdc20(b) M-Cdk(c) Securin(d) SeparaseI have been asked this question during an interview.My question comes from Mitosis Stages Overview in chapter Chromosomal Changes During Meiosis of Cytogenetics

Answer»

The correct choice is (C) Securin

For explanation I would SAY: Securin binds to separase unless it’s BROKEN down by Cdc20. This separase BREAKS down cohesion. The degradation of cohesion is also assisted by M-Cdk as it activates Cdc20. So, among these only securing PREVENTS Cohesin degradation.

88.

The reduction division of mitosis is _________________(a) The 1^st division(b) The 2^nd division(c) The G2 phase(d) The telophaseThis question was addressed to me in a job interview.The query is from Meiosis Prophase 1 : Leptotene topic in portion Chromosomal Changes During Meiosis of Cytogenetics

Answer»

The correct answer is (a) The 1^st division

Best explanation: In the 1st division the chromosome number is reduced to half as the homologous pair separates to OPPOSITE POLE. On the other HAND in 2^nd division the number of chromosome is CONSTANT just the chromatids separate like NORMAL mitosis.

89.

Mitosis occurs in _________(a) Nephron(b) Hair follicles(c) Neurons(d) OvaryThe question was posed to me during an interview.Question is taken from Mitosis Stages Overview topic in division Chromosomal Changes During Meiosis of Cytogenetics

Answer»

Right choice is (b) Hair follicles

To EXPLAIN I would SAY: Mitosis OCCURS in proliferative somatic cells. This doesn’t occur in ovary where OOGENESIS is via meiosis, and nephron and neurons don’t proliferate. Mitosis occurs in a hair follicle.