Bio Lab Final - Cell Division | Interphase, Mitosis, Cytokinesis

Which stages does the Cell Cycle consist of?

1. Interphase

   1. Gap 1 Phase (G1)

   2. Synthesis Phase (S)

   3. Gap 2 Phase (G2)

2. M Phase

   1. Mitosis

   2. Cytokinesis

What happens in Interphase?

The cell grows, copies its DNA, and prepares for mitosis by duplicating any necessary organelles.

What are the 3 phases of interphase?

1. First Gap (G1) Phase

2. Synthesis (S) Phase

3. Second Gap (G2) Phase

What happens in the G1 phase?

• Cell growths

• All organelles including centrioles duplicate

What happens in the S phase?

• DNA is synthesized

• Centrosomes (contain centrioles) duplicate

When the cell is in interphase, where is the DNA located?

In the nucleus

What happens in the G2 phase?

• Additional cell growth

What is the G0 phase?

A resting phase in which a cell is not preparing for the cell division cycle. This can be permanent, but sometimes the cell goes to G1.(The cell doesn’t divide or go through the cycle.)

What does the M Phase consist of?

1. Mitosis

2. Cytokinesis

What are the 4 phases of mitosis?

1. Prophase

2. Metaphase

3. Anaphase

4. Telophase

What happens in Prophase?

• Chromatin condenses and shortens (becomes chromosomes or a pair of sister chromatids)

• The nuclear envelope breaks down

• Centrioles form spindle fibers

At what region do sister chromatids attach?

At the centromere

What happens in Metaphase?

• Chromosomes line up at the metaphase plate

• Each sister chromatid is attached to a spindle fiber from opposite poles

What happens in Anaphase?

• Spindle fibers attach to kinetochores of each chromosome

• Chromatids are separated and pulled apart toward opposite ends of the cell

What is a kinetochore?

A specialized protein structure on a centromere to which spindle fibers attach.

What happens in Telophase?

• Nuclear membranes reform around each group of chromatids

• 2 nuclei form

• Organelles start to reappear

What happens in Cytokinesis?

• Division of parent cell cytoplasm into 2 daughter cells

• Cell membranes form

What is the difference between a plant and animal cell during cytokinesis?

In animal cells, a cleavage furrow is present in between the two daughter cells when splitting.

In plant cells, a cell plate is present in between the two daughter cells when splitting.

Are the resulting daughter cells in mitosis diploid or haploid?

Diploid

What does meiosis consist of?

Two nuclear divisions that reduce the number of chromosomes to the haploid number, in preparation for sexual reproduction.

1. Meiosis I

2. Meiosis II

What do Meiosis I and Meiosis II consist of?

• Prophase I & II

• Metaphase I & II

• Anaphase I & II

• Telophase I & II
  

What happens in Prophase I?

• Chromatin condenses to form chromosomes (in mitosis)

• Homologous chromosomes form pairs known as tetrads/bivalent

• Crossing over occurs (genetic material is exchanged)

• Chromosomes form a new combination of genes

(The last 4 points also occur in mitosis)

• Chromatin condenses to form chromosomes

• Nuclear membrane disappears

• Nucleolus disappears

• Centrioles move to opposite ends

• Spindle fibers start to form

Define Crossing Over

The mechanism by which linked genes undergo recombination. The exchange of corresponding segments between two homologous chromatids.

Define Chiasmata

An X-shaped connection between paired homologous chromosomes in prophase I of meiosis.

Define Chiasma

The visible manifestation of crossing over between homologous chromosomes.

What happens in Metaphase I?

• Instead of individual chromosomes aligning at the equatorial plane, homologous pairs align at the plane

• Each chromosome from the pair is tied to a spindle fiber from opposing sides

  • Centromere doesn’t separate

  • Sister chromatids are still together

What happens in Anaphase I?

• Homologous chromosomes separate and are pulled to opposite sides

• Spindle fiber shortens

What happens in Telophase I?

• Homologous chromosomes arrive at opposite ends

• Each pole contains half the number of chromosomes (haploid)

• Nuclear membrane is formed

• Nucleoli reappear

• Spindle fiber disappear

• Cytokinesis follows