Cell Cycle Cell Division Flashcards
What is cell cycle?
Events in which cell duplicates its genome and other contents and eventually divides into daughter cells.
Duration of cell cycle in
1️⃣Bacteria
2️⃣Yeast
3️⃣Human cells
Bacteria = 20min
Yeast =90min
Human cell = 24hrs
Duration of interphase is
Almost 95% of the total duration of cell cycle.
Which is the intense phase related to growth
Interphase.
Events that occur in G1 phase are:
Most Organelles duplicate.
Cell is metabolically active and grows continuously.
Events that occur in S phase are
DNA 🧬 replication .
Histone protein synthesis
Centriole replication
Sub-units for kinetochore are synthesized.
Duration of G1 phase in humans is ______, S phase is _____ and G2 phase is
G1 phase= 10hrs
S phase= 9hrs
G2 phase= 4hrs
Events that occur in G2 phase are
Proteins and RNA synthesis continues.
Tubulin protein is synthesized.
Final preparation for M-phase occurs.
Events in Go- phase are
Cell is metabolically active but no longer proliferates.
Cell decides to enter Go phase in M-phase.
Name the 4 stages of karyokinesis?
Prophase Metaphase Anaphase Telophase (Prof. Mehmood ah. Tak)
Events of early prophase are
Chromatin condensation occurs
Centriole pair start separating
Chromosome ends are not clearly visible.[spireme stage]
Viscosity increases.
Events in mid prophase
Centriole pair moves farther apart.
Chromatin condensation occurs.
# Aster formation starts.
Events in late prophase are
Spindle formation is ‘almost’ completed.
Aster formation ‘almost’ complete.
Chromosomes are fully condensed.
Events that occur in pro-metaphase
Aka 5th phase
Aster formation completed.
Spindle formation completed.
Mitotic apparatus (spindle & aster) is formed.
Events in metaphase are
▪️Congression metakinesis ( process of bringing of chromosomes from different locations towards equator).
▪️Chromosomes are fully condensed.
▪️Only metaphasic plate or equatorial plate is formed.
Chromosomes are attached with spindle fibres with the help of ___________
Kinetochores.
Events of anaphase are
Centromeric division occurs = Separation of sister chromatids = now called Chromosomes
DOUBLING OF CHROMOSOME NUMBER.
Best stage to study the shape of chromosomes are
Anaphase
Best stage for studying chromosome morphology is
Metaphase.
Match the following: 1️⃣Metacentric I 2️⃣Sub-metacentric. J 3️⃣Acrocentric L 4️⃣Telocentric V
Metacentric = V shaped
Sub metacentric = L shaped
Acrocentric = J shaped
Telocentric = I shaped
Rate of anaphasic movt. Of chromosomes is
0.2 - 5 μm/min
Number of ATP molecules used by a chromosome to reach the pole is
25ATP
Events that occur in telophase are
Chromosomes start de condensation .
Spindle and aster disappear.
Viscosity dcereases.
At the end, 2 nuclei are present in the same cell.
In animal cells cytokinesis occurs by ______method.
Cleavage forrow method.
To explain this method contractile ring theory was given by Dauglas Marshland.
Invagination in contractile ring theory is ________.(centripetal/centrifugal type)
Centripetal type( towards centre).
Cytokinesis in plants occurs by ________ method.
Cell plate method.
Cell plate method is
a) Centripetal type
b) Centrifugal type
c) Niether a) nor b)
Centrifugal type.
Initial signs for cytokinesis are observed in _______ phase
Late anaphase.
_______ gives rise to middle lamella formation (by cell plate method).
Mainly Golgi apparatus.
Sometimes ER.
What is phragmoplast?
In cell plate method, vesicles sent by golgi are trapped at the centre by spindle and the complex thus formed is called phragmoplast.
Which of them is/are mitotic poison: 1️⃣Ribonuclease 2️⃣Azide & cyanide 3️⃣Mustard gas 4️⃣Chalones
All of them. ▪️Ribonuclease = inh. at prophase ▪️Azide & cyanide = inh. at prophase ▪️Mustard gas = agglutination of chromosomes ▪️Chalones = these are glycoproteins.
Match the following:
▪️Ribonuclease agglutination of chromosomes
▪️Azide & cyanide these are glycoproteins
▪️Mustard gas inh. at prophase
▪️Chalones inh. at prophase
▪️Ribonuclease = inh. at prophase
▪️Azide & cyanide = inh. at prophase
▪️Mustard gas = agglutination of chromosomes
▪️Chalones = these are glycoproteins.
Which of them is correct:
1) Meiosis always occurs in diploid cell.
2) Meiosis always occurs in haploid cell.
3) Meiosis can occur in either haploid or diploid cell.
Only statement 1) is correct.
Meiosis always occurs in diploid cell but not in haploid cell.
Which cells undergo meiosis?
Only cells of sexually reproducing organisms undergo meiosis.
* Some special cells (gonad cells) switch rom mitosis to meiosis in certain stage of their life.
Meiosis involves ______ cycles of karyokinesis and _______ cycles of DNA replication.
2 cycles of karyokinesis
1 round/ cycle of DNA replication
Interphase of meiosis has longer \_\_\_\_phase and short or no \_\_\_\_\_phase. 1️⃣s phase , G2 phase 2️⃣M phase , S phase. 3️⃣G1 phase ,M phase 4️⃣G2 phase, S phase
Opt 1
Longer s phase and short or no G2 phase.
Chromatin condensation starts in
Leptotene or leptonema aka Bouquet stage.
Synapsis occurs in
Zygotene or synaptotene or zygoneme.
What is synapsis or syndesis?
Pairing of homologous or maternal and paternal chromosomes is c/d synapsis or syndesis.
Formation of tetrad or bivalent occurs in
Zygotene.
Synaptonemal complex is formed due to
Involvement of nuclei proteins or synaptonemal complex proteins(SCP) e.g, SCP-1, SCP-2, SCP-3. # it was first observed by Moses.
Crossing over or recombination occurs in
Pachytene
What’s crossing over or recombination?
Exchange of chromatin segments b/w non-sister chromatids of homologous chromosomes is c/d crossing over. # first observed by Morgan in Drosophila.
Chiasma is observed in
Diplotene.
What is chiasma or chiasmata?
Homologous chromosomes start separating from each other except at cross- over point c/d chiasma.
What is dictyotene?
In vertebrates and invertebrates, diplotene is metabolically active and is extended (duration very high), and is called dictyotene. # extending cell can range from months upto years. # observed in primary oocytes.
Separation of homologous Chromosomes is called
De-synapsis. #occurs in diplotene.
Terminalisation of chiasma occurs in
Diakinesis
Events in diakinesis are
Terminalisation of chiasma.
At the end, chromosomes are fully condensed.
Spindle and aster formation is completed.
What is dyad?
Two cells formed after meiosis-1 are called dyad.
What is disjunction?
The separation of homologous chromosomes is called disjunction.
Why is meiosis-1 called as reductional division?
Meiosis 1 is called as reductional division because chromosomes are reduced to half in dyad cell.
Events that occur in metaphase-1 are
Bivalents are arranged at equator.
2 metaphasic plate are formed.
Maternal and paternal chromosomes are arranged randomly on equator.
Stages of prophase-1, in order, are
- Leptotene
- Zygotene
- Pachytene
- Diplotene
- Diakinesis
