XI: Chapter 10- Cell cycle and cell division Flashcards
In the 24 hours duration of human cell cycle how long does cell division proper last?
One hour
In which phase do the centrioles duplicate?
S phase
What occurs in G2 phase?
Protein synthesis
Which is the most dramatic period of cell cycle?
M phase
When do centrioles move towards the opposite poles?
In prophase
Asters are made of
Microtubules
What forms the mitotic apparatus?
Asters along with the mitotic spindle
In which phase of cell cycle is morphology of chromosomes best studied?
Metaphase
What serves as site for attachment of spindle fibres?
Kinetochores
Where does the wall formation start during cytokinesis in cell?
From the centre towards the periphery
What is the precursor of cell wall?
Cell plate
Cell plate represents
Middle lamella
Synapse formation in meiosis occurs in which phase?
Zygotene of meiosis I
Bivalents are formed in which stage of meoisis?
Zygotene of meoisis I
Bivalents are visible clearly in which phase of meiosis?
Pachytene of meiosis I
What marks the beginning of diplotene?
Dissolution of synaptonemal complex
Chiasmata formation occurs in which phase of meiosis?
Diplotene
When is a dyad of cells formed in meoisis?
Telophase I
Who discovered amitosis?
Flemming
What happens to nuclear membrane during amitosis?
It remains intact
In which phase does atp synthesis occur in mitosis?
G1
When does histone doubling occur in cell cycle?
S-phase
When does tubulin synthesis occur?
G2
How many check points are present in cell cycle?
Three- G1 checkpoint, G2 checkpoint, Metaphase-anaphase checkpoint
When is CDK (Cyclin-dependent kinase) activated?
G1 checkpoint
What are chalones?
Tissue specific suppressant, inhibitor of cell cycle
What are the three types of spindle fibres?
Continuous/interpolar fibre (from one pole to another)
Internodal (between two centromere)
Tractile (between pole and centromere)
Which is the best material to study meiosis?
Pollen mother cell
What change occurs in number of chromosomes at the end of meiosis I ?
Chromosome number reduces to half
What change occurs in dna content at the end of meiosis I ?
DNA content remains the same as parent
At the end of meiosis II what happens to dna and chromosomal content?
Dna content reduces to half and chromosome number remains same as meiosis I
Following DNA replication in S-phase, the DNA content becomes 4c and a pair of sister chromatids are formed from each chromosome. What is the number of chromosomes? Why?
The number of chromosomes is 2n before and after DNA replication because a pair of sister chromatids is counted as one chromosome.
So even when DNA content doubles leading to the formation of sister chromatids in each chromosome, chromosome number remains the same.
The chromosome number in a diploid cell (2n) remains the same (2n) even after replication of DNA in S-phase, then how do the two cells formed at the end of mitosis have 2n chromosomes each?
When DNA replicated each chromosome develops a pair of sister chromatids. The chromosome is still counted as a single chromosome (with a pair of sister chromatids). When the cell undergoes M phase, the sister chromatids separate and so each daughter cell has 2n ploidy.
How many chromatids does diploid cell (2n) have?
2n
How many chromatids does a diploid cell have after s-phase?
4n
How many arms does y chromosome have?
1
How many arms does x chromosome have?
2
