This set of Cytogenetics Multiple Choice Questions & Answers (MCQs) focuses on “Overview of Cell Reproduction”.
1. In cells the DNA replication takes place in _____________ phase.
a) G0
b) G1
c) S
d) G2
View Answer
Explanation: 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.
2. The cells before permanently differentiating enters into ______________ phase.
a) G1
b) G2
c) G0
d) S
View Answer
Explanation: Before permanent differentiation the cells enter into G0 phase where they don’t continue with the cell cycle. This immediately follows G1 phase.
3. Eggs in female stay in ______________ phase for extended duration.
a) S
b) G1
c) G2
d) M
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Explanation: 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.
4. Which of the following will prevent cell cycle from progressing in case of DNA damage?
a) P53
b) G1 cyclin
c) P10
d) Bcl-2
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Explanation: 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.
5. 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 off
View Answer
Explanation: Cln3 in yeast induces replication. If replication is more than cell growth, it will lead to gradual decrease in cell size.
6. 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 Rb
View Answer
Explanation: 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.
7. The concentration of which of the following varies during the cell cycle?
a) Cdk
b) Cyclin
c) SCF
d) Proteosome
View Answer
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.
8. Which of the following is an activation process?
a) Wee1 kinase
b) APC
c) Cdc25
d) p27 binding
View Answer
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.
9. 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 lysis
View Answer
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.
10. P53 requires ________________for its activity.
a) Mdm
b) MCM
c) Securin
d) Cdt
View Answer
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.
11. 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-Cdk
View Answer
Explanation: M-Cdk itself promotes the ubiquitine lygase that marks M-cyclin for destruction, thereby inactivating M-Cdk. This helps in anaphase.
12. What is a negative regulator of Cdc-20?
a) M-Cdk
b) Mad-2
c) Mdm
d) Hct1
View Answer
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.
Sanfoundry Global Education & Learning Series – Cytogenetics.
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