Cell Division - Mitosis and Meiosis

The regular sequence of growth and division that cells undergo.

What is the cell cycle?

The cells that result when a cell divides.

What are daughter cells?

Replication

In what process does the cell make a copy of its DNA?

Chromosomes

What two-rod structures contain the cell's DNA?

Chromatid

What is each rod called?

Stringy substance that consist of DNA tightly coiled around proteins before it forms into chromosomes.

What is chromatin?

One of two identical "sister" parts of copied chromosomes.

What is a chromatid?

The structure that holds the two chromatids together.

What is a centromere?

Centrioles have spindle fibers attached to them.

What is a centriole?

Closer image of a centriole.

Asexual reproduction (cell division) of a body cell where one copy of DNA is distributed into each of the two daughter cells.

What is Mitosis?

Daughter cells are identical to the parent cell.

Purpose: To repair or replace body cells.

Mitosis only occurs in eukaryotic cells.

One continuous process. After Telophase, the division cycle starts again with Interphase.

Interphase

What are the stages of Mitosis?

Prophase

Metaphase

Anaphase

Telophase

The cell grows, replicates its DNA, and prepares to begin mitosis.

What happens during Interphase?

Chromatin forms into chromosomes.

What happens during Prophase?

Centrioles move to opposite sides and send out

spindle fibers.

Nuclear membrane (envelope) breaks down.

Each spindle fiber attaches to a chromatid pair at its centromere to line them up across the MIDDLE of the cell.

What happens during Metaphase?

MIDDLE \= METAPHASE

The spindle fibers SPLIT APART the sister chromatids and move them to opposite ends of the cell, equally dividing the genetic material.

What happens during Anaphase?

APART \= ANAPHASE

A nucleolus forms in each side.

What happens during Telophase?

A new nuclear membrane forms around each new set of chromosomes, each with the same number of chromosomes as the original cell.

Cytokinesis finishes the process by splitting the cell in 2.

The division cycle begins again with Interphase

The cytoplasm divides, distributing the organelles into each of the two new cells.

What happens during cytokinesis?

Cytokinesis finishes the division process. The cell membrane squeezes together around the middle of the cell until the cell is pinched in two, splitting the cell in two and dividing the cytoplasm, organelles, and other material contained within the cell.

What happens during cytokinesis of animal cells?

A cell plate forms across the middle of the cell and gradually develops into new cell membranes, and new cell walls form around the cell membranes.

What happens during cytokinesis of plant cells?

Because of the rigid cell wall, the cell membrane cannot be pinched inward like cytokinesis happens in animal cells.

Only for sexual reproduction.

What is meiosis?

Stages of gamete cell reproduction.

Interphase I

What are the stages of meiosis?

Prophase I

Metaphase I

Anaphase I

Telophase I

Prophase II

Metaphase II

Anaphase II

Telophase II

This happens before mitosis or meiosis. The cell grows, replicates its DNA, and prepares to begin mitosis or meiosis.

Interphase

1. Chromosomes condense.

Prophase I

2. Sister chromatids pair up.

3. Crossing over occurs.

4. New combos of alleles are formed.

5. Spindle fibers form at opposite ends of the cell.

6. Nuclear membrane disappears.

Homologous chromosomes line up at the center of the cell.

Metaphase I

(Metaphase\=They MEET in the MIDDLE)

Spindle fibers from one end of the cell attach to the homologous chromosomes, and spindle fibers from the other end attach to the chromatid pairs.

Homologous chromosomes separate and MOVE APART to opposite sides of the cell.

Anaphase I

The sister chromatids remain attached at their centromeres. This is different than in mitosis.

Each side has a set of haploid set of chromosomes.

Telophase I

Each chromosome still has 2 chromatids.

Nuclear membrane forms around the 2 daughter cells.

The cell splits into 2 daughter cells with 2 chromatids in each. The chromosomes are different from each other and from the parent diploid cell because of the crossing over that occurred in Prophase I.

Cytokinesis in Meiosis

Nuclear membrane breaks down.

Prophase II

New spindle fibers form

Chromosomes line up at the MIDDLE of the cell.

Metaphase II

Spindle fibers attach to centromeres.

Centromeres separate and the spindle fibers contract and pull sister chromatids apart to opposite ends of the cell.

Anaphase II

A nuclear membrane forms around each haploid set of chromosomes.

Telophase II

The cells divide forming into haploid gametes, 4 sperm or 1 egg cell. (Remember, 3 egg cells die off.)

cytokinesis

So 4 haploid daughter cells formed from the original diploid cell when it entered Meiosis.

1 diploid cell → Meiosis → 4 haploid daughter cells (gametes)

Cytokinesis finishes the division process by splitting the cell in two and dividing the cytoplasm, organelles, and other material contained within the cell. Cytokinesis differs in plant and animal cells.

What is cytokinesis?

Deoxyribonucleic acid

What does DNA stand for?

The two strands in one molecule separate, and then new nitrogen bases pair up with each strand to form two molecules of DNA.

What happens in DNA replication?

Adenine, Thymine, Cytosine, & Guanine

Name the four nitrogen bases in DNA.

Adenine always pairs with Thymine.

Name the nitrogen base pairs.

Cytosine always pairs with Guanine

A twisted ladder called a Double Helix.

What is the shape of a DNA molecule?

Mitosis or Meiosis?

Meiosis

The process of nuclear division in cells during which the number of chromosomes per cell is reduced by half through the separation of homologous chromosomes. Sexual reproduction.

Mitosis or Meiosis?

Mitosis

A process of nuclear division in eukaryotic cells during which the nucleus of a cell divides into two nuclei, each with the same number of chromosomes.