AP Syllabus focus:
‘Sister chromatids separate in anaphase II, then decondense as cytokinesis forms four genetically distinct haploid daughter cells.’
Meiosis II completes the physical separation of genetic material into individual gametes. Its final stages—anaphase II, telophase II, and cytokinesis—convert duplicated chromosomes into single-chromatid chromosomes in four cells.
Overview diagram of meiosis I and meiosis II, highlighting that meiosis II resembles mitosis in that sister chromatids (not homologous chromosomes) separate. The figure also connects anaphase II through telophase II and cytokinesis to show how four haploid cells end up with single-chromatid chromosomes. Source
Starting point for anaphase II
Each of the two cells entering these stages contains chromosomes that are already positioned for separation and connected to the spindle apparatus through kinetochore attachments.
Sister chromatid: one of two identical DNA copies produced during replication and held together until they are separated into different cells.
A key idea is that separation now occurs between sister chromatids (not between homologous chromosomes), creating genomes with one chromatid per chromosome.
Anaphase II: sister chromatids separate
Anaphase II begins when the connection between sister chromatids is released, allowing them to behave as independent chromosomes.
Stage chart summarizing meiosis I and meiosis II, including anaphase II and telophase II, so students can visually track when chromatids split and when nuclei reform. This is helpful for distinguishing the separation event in meiosis II from homolog separation in meiosis I. Source
What happens mechanically
Cohesion is lost at the centromere region, so sister chromatids are no longer physically paired.
Kinetochore microtubules shorten, pulling chromatids toward opposite poles.
Non-kinetochore microtubules help maintain cell shape and pole spacing as chromatids move.
What to track as chromatids move
Once separated, each sister chromatid is considered an individual chromosome.
Movement is directional: one chromatid to each pole, producing two equivalent chromosome sets at opposite ends of the cell.
Accurate separation ensures each future gamete receives one copy of each chromosome (as single chromatids).
Haploid (n): having one complete set of chromosomes, with one copy of each chromosome type.
Telophase II: nuclei reform and chromosomes decondense
Telophase II occurs after chromatids have reached opposite poles, shifting the cell from chromosome movement to chromosome packaging and compartmentalisation.
Cellular changes in telophase II
Chromosomes begin to decondense, making DNA less tightly packed.
Nuclear envelopes re-form around each set of chromosomes (when typical for the organism/cell type), creating distinct nuclei.
The spindle apparatus disassembles, since chromosome separation is complete.
These events restore nucleus-like organisation around each haploid genome, setting up the final physical division of the cytoplasm.
Cytokinesis: formation of four genetically distinct haploid daughter cells (gametes)
Cytokinesis divides the cytoplasm so that each nucleus and its haploid chromosome set occupy a separate cell.
How cytokinesis produces four cells
Each of the two cells undergoing meiosis II splits once.
The end result is four haploid daughter cells, each containing:
one set of chromosomes (n)
each chromosome as a single chromatid
Why the four products are genetically distinct
Even though anaphase II is a separation event, the four daughter cells are typically genetically distinct because each cell contains a different combination of chromatids (and therefore alleles) from the original duplicated set present at the start of meiosis II.
Key outcomes to state precisely
Anaphase II: sister chromatids separate to opposite poles.
Telophase II: chromatids (now chromosomes) decondense; nuclei may re-form.
Cytokinesis: partitions the cell to create four genetically distinct haploid daughter cells that function as gametes in sexually reproducing organisms.
FAQ
It typically involves activation of regulatory proteins that allow proteolysis of centromere-associated cohesion proteins.
This removes the physical linkage so spindle forces can pull chromatids apart.
Not always; it depends on species and cell type.
In some cells, nuclear envelope re-formation is brief or altered to accommodate rapid gamete maturation.
Because once separated, each chromatid has its own centromere and is inherited independently.
Functionally, it is now a complete chromosome unit for a daughter cell.
Animals commonly form a cleavage furrow via an actin–myosin contractile ring.
Plants commonly build a cell plate that becomes a new cell wall partition.
Not necessarily.
Some may be nonfunctional due to developmental pathways or errors during chromatid separation, even if meiosis II completes structurally.
Practice Questions
State what separates during anaphase II and describe the chromosome content of each cell after cytokinesis at the end of meiosis II. (2 marks)
Sister chromatids separate during anaphase II. (1)
Four haploid cells are produced, each with one set of chromosomes made of single chromatids. (1)
Describe the sequence of events from anaphase II through telophase II and cytokinesis that leads to the formation of four genetically distinct gametes. (5 marks)
Cohesion between sister chromatids is released and chromatids separate. (1)
Spindle/kinetochore microtubules shorten to move chromatids to opposite poles. (1)
Chromatids reach poles and are then considered individual chromosomes. (1)
Nuclear envelopes re-form and chromosomes decondense during telophase II. (1)
Cytokinesis divides the cytoplasm to produce four haploid, genetically distinct daughter cells (gametes). (1)
