4.1 Meiosis-I Flashcards
Topic - Prophase-I
The Prophase of the first meiotic division is the same compared to prophase of mitosis.
T/F
False,
Prophase of the first meiotic division is typically longer and more complex.
Based on chromosomal behavior, Prophase-I is divided into:
I. Leptotene
II. Zygotene
III. Pachytene
IV. Diplotene
V. Diakinesis
Topic - Leptotene (Leptonema)
The chromosomes become gradually visible under the light microscope.
T/F
True
The compaction of chromosomes continues throughout leptotene.
T/F
True
Key events of Leptotene:
I. Chromatin fibers become long slender chromosomes.
II. Nucleus enlarges.
Topic - Zygotene (Zygonema)
Similar chromosomes start ______ (splitting/pairing) together.
This process of pairing is called ______.
pairing; synapsis
Chromosome synapsis is accompanied by the formation of a complex structure called.
Synaptonemal complex
The paired chromosomes are called.
Homologous chromosomes
The complex formed by a pair of synapsed homologous chromosomes is called ______, which is more clearly visible in the next stage (Pachytene).
Bivalent or tetrad
The two short-lived stages of prophase-I are _____ and _____ compared to Pachytene.
Leptotene and zygotene
Topic - Pachytene (Pachynema)
Four chromatids of each bivalent chromosome become distinct and clearly appear as
Tetrads
The Pachytene stage is characterized by the appearance of ______.
Recombination nodules (Sites at which crossing over occurs)
The sites at which crossing over occurs between non-sister chromatids of the homologous chromosomes are called.
Recombination nodules
The process of exchanging genetic material between two homologous chromosomes is called.
Crossing over
Crossing over is also an enzyme-mediated process, and the name of the enzyme is called.
Recombinase
Crossing over leads to the recombination of genetic material on the two chromosomes.
T/F
True
At the end of pachytene, recombination between homologous chromosomes is completed which leaves the chromosomes linked at the sites of crossing over.
T/F
True
Topic - Diplotene (Diplonema)
What happens at the beginning of the Diplotene stage?
The dissolution of the synaptonemal complex occurs.
The tendency of homologous chromosomes of bivalent to separate from each other except at the site of _____.
crossovers
The X-shaped structure formed after crossing over is called.
Chiasmata
Diplotene can last for months or years in ______ of some vertebrates.
Oocytes
Topic - Diakinesis
Diakinesis is marked by -
Terminalisation of chiasmata
In Diakinesis, chromosomes are fully condensed.
T/F
True
The meiotic spindle is assembled to prepare the homologous chromosomes for ______.
separation
By the end of diakinesis, ______ disappears, and ______ also breaks down.
Nucleolus; Nuclear envelope
Diakinesis represents a transition to metaphase.
T/F
True
Topic - Metaphase-I
In Metaphase-I, Spindle formation is completed.
T/F
True
The bivalent chromosomes align on the equatorial plate.
T/F
True
______ from the opposite poles of the spindle attach to the kinetochore of homologous chromosomes.
Microtubules
Topic - Anaphase-I
Main events of Anaphase-I :
I. Homologous chromosomes separate
II. Sister chromatids remain associated at their centromeres.
Topic - Telophase-I
In Telophase-I, ______ and ______ reappear.
Nuclear membrane; Nucleolus
______ is called when two haploid daughter nuclei are formed, then cytokinesis happens.
Dyad of cells (Diad)
Although, in many cases, the chromosomes do undergo some dispersion. They do not reach the extremely extended state of the interphase nucleus.
T/F
True
The short-lived stage between two meiotic divisions is called.
Interkinesis
There is no replication of DNA during interkinesis.
T/F
True
Prophase-II follows Interkinesis
T/F
True
