Chapter 4 Mitosis and Meiosis Flashcards
What is the primary function of Interphase in the cell cycle?
The cell grows and prepares for division
Interphase constitutes about 90% of the cell cycle.
What percentage of the cell cycle does the Mitotic (M) Phase occupy?
10%
The M phase involves the division of the cell into two identical daughter cells.
What occurs during the G1 (Gap 1) Phase of Interphase?
Cell grows and carries out normal functions; organelles duplicate
This phase focuses on cell growth and preparation for DNA synthesis.
During which phase does DNA replication occur?
S (Synthesis) Phase
In humans, chromosomes duplicate from 46 to 92 chromatids.
What is the main event in the G2 (Gap 2) Phase?
Cell prepares for division by making proteins and checking for errors
This phase ensures that the cell is ready to enter mitosis.
What happens during Prophase of mitosis?
Chromatin condenses into chromosomes; nuclear envelope breaks down; mitotic spindle forms
Centrioles move to opposite poles of the cell.
What is the significance of Metaphase in mitosis?
Chromosomes align at the metaphase plate; spindle fibers attach to centromeres
Ensures that sister chromatids will be pulled to opposite poles.
What occurs during Anaphase?
Sister chromatids separate and move toward opposite poles of the cell
This ensures each daughter cell receives an identical set of chromosomes.
What happens in Telophase?
Separated chromatids reach the poles and de-condense into chromatin; nuclear envelope re-forms
Results in two distinct nuclei within the cell.
Cytokinesis is defined as what process?
The division of the cytoplasm resulting in two separate daughter cells
Often occurs concurrently with telophase.
What is the primary purpose of Meiosis I?
Reduction division
It reduces the chromosome number by half, resulting in haploid cells.
What occurs during Prophase I of meiosis?
Chromatin condenses into chromosomes; homologous chromosomes pair up; crossing over occurs
This increases genetic diversity.
What happens during Metaphase I?
Homologous chromosome pairs align at the metaphase plate; spindle fibers attach to centromeres
Independent assortment occurs, increasing genetic variation.
What is unique about Anaphase I compared to Anaphase in mitosis?
Homologous chromosomes separate; sister chromatids remain attached
This is a key difference in the mechanisms of meiosis.
What occurs during Telophase I and Cytokinesis?
Chromosomes arrive at opposite poles; nuclear membranes may reform; cell divides into two haploid daughter cells
This concludes the first meiotic division.
What is the main similarity between Meiosis II and Mitosis?
Both involve the separation of sister chromatids
Meiosis II is often referred to as a mitotic-like phase.
What happens during Prophase II?
Chromosomes condense again; spindle fibers reform; nuclear envelope breaks down
This occurs if the nuclear envelope was reformed in Telophase I.
What is the outcome of Telophase II and Cytokinesis?
Four haploid daughter cells with unique genetic material are formed
Each cell contains a different combination of chromosomes.
What are the stages of Mitosis?
Prophase
Metaphase:.
Anaphase:
Telophase
Cytokinesis
What are the Cell Cycle Stages
Interphase (90% of the cycle) – The cell grows and prepares for division.
Mitotic (M) Phase (10% of the cycle) – The cell divides into two identical daughter cells.
What are the Interphase (Growth & DNA Replication) Stages
G1 (Gap 1) Phase:
Cell grows and carries out normal functions.
Organelles duplicate.
S (Synthesis) Phase:
DNA replication occurs.
Chromosomes duplicate (from 46 to 92 chromatids in humans).
G2 (Gap 2) Phase:
Cell prepares for division by making proteins and checking for errors.
What are the Meiosis I (Reduction Division) stages?
Prophase I
Chromatin condenses into chromosomes.
Homologous chromosomes pair up (synapsis) and form tetrads.
Crossing over occurs, exchanging genetic material between homologous chromosomes.
Spindle fibers begin to form, and the nuclear envelope breaks down.
Metaphase I
Homologous chromosome pairs (tetrads) align at the metaphase plate.
Spindle fibers attach to the centromeres.
Independent assortment occurs, increasing genetic variation.
Anaphase I
Homologous chromosomes separate and move to opposite poles.
Sister chromatids remain attached at their centromeres.
Telophase I & Cytokinesis
Chromosomes arrive at opposite poles.
Nuclear membranes may reform, and the cell divides into two haploid daughter cells
What are the Meiosis II (Similar to Mitosis) stages?
Prophase II
Chromosomes condense again if necessary.
Spindle fibers reform, and the nuclear envelope breaks down (if reformed in telophase I).
Metaphase II
Chromosomes (composed of sister chromatids) align at the metaphase plate.
Spindle fibers attach to centromeres.
Anaphase II
Sister chromatids separate and move toward opposite poles.
Telophase II & Cytokinesis
Chromatids arrive at opposite poles, and the nuclear envelope reforms.
The cytoplasm divides, resulting in four haploid daughter cells with unique genetic material.
