Unit 3: Cell Division

somatic cells
Somatic cells consist of all the nonreproductive cells in an organism; for example, tissue cells, nerve cells, and blood cells. When somatic cells divide, they go through the process of mitosis, which is a type of cell division that results in two identical daughter cells.

Module 14: Types of Cells

Module 14: Types of Cells
(1) Explain the functional differences between somatic cells and gametes.

(2) Explain why somatic cells and gametes are produced using different cell replication processes.

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Meiosis
a type of cell division that prepares an organism for sexual reproduction. Meiosis begins with germ cells.

Module 14: Types of Cells

germ cells
germ cells are found in the ovaries and testes. These germ cells go through the process of meiosis to produce gametes, which in animals are sperm and egg cells.

Module 14: Types of Cells

gametes
sperm and egg cells in animals. When two gametes from different individuals combine, a unique new cell is produced, called a zygote

Module 14: Types of Cells

zygote
goes through the process of mitosis to grow into a new individual

Module 14: Types of Cells

True or False: A single gamete can grow into a zygote through the process of mitosis
False: A single gamete becomes a zygote only when it is combined with (or fertilized by) another gamete

Module 14: Types of Cells

Eggs and sperm are what type of cells?
Gametes

Eggs and sperm are the reproductive cells of an organism that are produced through meiosis from germ cells. Eggs and sperm join together through fertilization to produce a zygote.

Module 14: Types of Cells

A zygote grows into an organism through what process?
Mitosis

A zygote is the cell formed when a sperm fertilizes an egg. Zygotes grow into adult through countless rounds of mitosis, which produces two identical daughter cells from a single cell.

Module 14: Types of Cells

Gametes are produced from what type of cell?
Germ

Germ cells undergo meiosis to produce gametes (eggs and sperm). Germ cells are the progenator cells for eggs and sperm found in the ovaries and testes, respectively.

Module 14: Types of Cells

Differentiation
Certain genes found in a cell’s nucleus are turned on or off. Even though every single somatic cell in your body contains identical DNA, these cells were able to differentiate into specific cell types (such as blood cell, liver cells, etc.) simply by turning certain genes on or off.

This is how a single cell can grow into a complex adult organism containing many different cell types simply by mitosis.

Module 14: Types of Cells

A skin cell is an example of:
A somatic cell

A somatic cell is a nonreproductive cell in a multicellular organism.

Module 14: Types of Cells

A skin cell would divide to make more skin cells using the process of:
Mitosis

Somatic cells like skin cells divide using mitosis.

Module 14: Types of Cells

Why must somatic cells be produced through mitosis?
Mitosis produces two daughter cells that are identical to the parental cell. This ensures the integrity of the cells genetic make-up, function, and type from one generation of cells to the next.

Module 14: Types of Cells

Why must gametes be produced through meiosis?
Meiosis produces 4 haploid, genetically distinct daughter cells called gametes. This ensures genetic diversity within a species through sexual reproduction.

Module 14: Types of Cells

Module 14: Basic Chromosome Structure
Describe the structure of a chromosome in different stages of the cell cycle.
Chromosomes
Thread-like structures located inside cells. n eukaryotic cells, the chromosomes are contained inside an organelle called a nucleus. In prokaryotic cells, they are located in a particular area of the cytoplasm. Chromosomes are made up of two major parts: DNA and proteins. Both DNA and proteins are large molecules.

Module 14: Basic Chromosome Structure

DNA
Deoxyribonucleic Acid
The nucleic acid that contains genetic instructions for making RNA and, ultimately, proteins in all living organisms. DNA is composed of two strands of nucleotides, which are intertwined in a double helix

The molecule that stores and transmits inherited genetic information. This information includes the directions that tell a cell how to make proteins. Information is stored in DNA in segments called genes.

Module 14: Basic Chromosome Structure

proteins
Organic macromolecules made up of amino acids connected by peptide bonds. Proteins serve many functions, some of which include: catalyzing reactions as enzymes, storage, replication, transmission, and regulation of genetic information, and helping maintain structure in an organism.

Module 14: Basic Chromosome Structure

genes
Module 14: Basic Chromosome Structure
histone protein molecules
These proteins associate with DNA in a very precise way. First, they couple with DNA at regularly spaced intervals. Second, they help to wind the DNA molecule into an organized and compact structure called a chromosome.

Module 14: Basic Chromosome Structure

What is the significance of winding function of histones?
It allows the DNA to be condensed into organized bundles (chromosomes) that can easily be moved around the cell. Because the DNA is wound around the histones in such an organized way, the DNA can be easily wound up and unwound at various points during the cell cycle.

Module 14: Basic Chromosome Structure

enzymes
A protein that acts as a catalyst for chemical reactions in biological organisms. Enzymes increase the speed of chemical reactions. They are proteins that bind to a chemical (called a substrate) and chemically modify the substrate into an end product. The substrate binds to the active site of the enzyme. Enzymes speed up the rate of chemical reactions that support life.

Module 14: Basic Chromosome Structure

Why is keeping the DNA organized critical?
Think of a long piece of string. Knots can easily form in the string if it is not carefully wound up into a ball. Keeping the DNA organized is critical, especially when you consider that the DNA in one human cell is three feet long when it is stretched out straight. This is quite amazing when you realize that this must fit into a cell so small that it cannot be seen with the naked eye.

Module 14: Basic Chromosome Structure

How is DNA organization competed?
One of these is the winding of DNA around histone molecules. As a result of this winding, the DNA molecule becomes shorter than before it was wound around the histone molecules.

Module 14: Basic Chromosome Structure

During the S phase of the cell cycle, DNA is replicated. What form would you expect the DNA to be in?
A loose pile.

DNA in chromatin form is easiest to replicate.

Module 14: Basic Chromosome Structure

During the M (mitosis) phase of the cell cycle, what form would you expect the DNA to be in?
Tightly wound around the histone proteins as chromosomes.

In this form the chromosomes are compact and easy to move as the new cells are forming.

Module 14: Basic Chromosome Structure

Module 14 : Counting Chromosomes
Distinguish between the structure and number of chromosomes in somatic cells, germ cells, and gametes.
homologue
The chromosomes in somatic cells and germ cells are present in pairs. One chromosome in each pair is descended from the organism’s father. The other chromosome in the pair is descended from the organism’s mother. Each member of a chromosome pair is called a homologue.

Together, these two chromosomes make up a pair of homologous chromosomes. The words homologue and homologous both begin with the prefix “homo-,” which means “the same or similar.” So the two chromosomes in each pair contain the same set of instructions.

Module 14 : Counting Chromosomes

mitosis
A type of cellular division in which a single, diploid, somatic cell is divided into two genetically identical daughter cells. Mitosis along with cytokinesis compose the mitotic (M) phase of the cell cycle.

Module 14 : Counting Chromosomes

Diploid
Referring to cells that contain two sets of chromosomes (i.e. pairs of homologous chromosomes). One set of chromosomes is inherited from the mother and the other set is inherited from the father. Diploid cells are 2n. Somatic and germ cells are diploid.

Somatic cells produced through mitosis are diploid. “Di-” means “two,” and diploid cells contain two copies of every chromosome

Module 14 : Counting Chromosomes

Chromosome
Tightly coiled form of the DNA-protein complex. A thread-like structure of nucleic acids carrying genetic information in the form of genes. Chromosomes are found in the nucleus of a eukaryotic cell and in the nucleoid region of a prokaryotic cell.

Module 14 : Counting Chromosomes

chromatin
The combination of DNA and proteins that fill the eukaryotic nucleus.

A combination of DNA and proteins that constitutes chromosomes. The term chromatin is used to refer to the extended form taken by the chromosomes when a eukaryotic cell is not dividing. When the cells divide, chromatin condenses and becomes visible as chromosomes.

Module 14 : Counting Chromosomes

How man chromosomes do humans have in their diploid cells?
46

“2n = 46”

Humans who have more or less than 46 chromosomes sometimes survive, but usually have life-altering conditions, such as Down syndrome. Down syndrome is caused by having three copies of chromosome 21, instead of the usual two copies

Module 14 : Counting Chromosomes

How many total chromosomes are found in one human somatic cell?
46

There are 22 pairs of autosomes (for a total of 44 autosomes) and one pair of sex chromosomes (for a total of two sex chromosomes). Add those up, and you have a grand total of 46 chromosomes in each somatic cell.

Module 14 : Counting Chromosomes

How many total chromosomes are found in one human zygote?
A zygote, with 46 chromosomes, goes through mitosis to produce somatic cells, each with 46 chromosomes.

Module 14 : Counting Chromosomes

Now take a wild guess: Remember that two gametes combine during fertilization to produce a single zygote. How many chromosomes do you think are in one human gamete?
23

Two human gametes, each with 23 chromosomes, will combine to form a zygote with 46 chromosomes.

Module 14 : Counting Chromosomes

haploid cells
Cells that contain only one set of chromosomes. Haploid cells are referred to as “1n”. Gametes (sperm and eggs) are haploid. In human haploid gametes contain 23 chromosomes.

In human haploid gametes, there are 23 chromosomes. One way to write this is “1n = 23.”

Module 14 : Counting Chromosomes

How many chromosomes are in the corn 2N cells (Gamete cell = 10)
20

2N is the total number of chromosomes in a diploid cell.

Module 14 : Counting Chromosomes

How many chromosomes are in a dog’s heart cells?
(Gamete cell = 39)
78

The diploid chromosome number is the number of chromosomes in somatic cells.

Module 14 : Counting Chromosomes

How many chromosomes are in an unfertilized goldfish egg (gamete cell = 52)?
52

The haploid number is in the column marked “chromosomes in gamete cells.”

Module 14 : Counting Chromosomes

How many chromosomes are in the cell that gave rise to the goldfish egg (gamete cell = 52)?
104

This is the diploid number. Unfertilized eggs are gametes and must be haploid, but the cell that gives rise to the gametes is diploid.

Module 14 : Counting Chromosomes

Somatic corn cells have 20 chromosomes. This means that in corn, _________.
2n = 20

2n is the total number of chromosomes in a diploid, somatic cell.

Module 14 : Counting Chromosomes

n a dog, 2n = 78. How many chromosomes are in a dog’s heart cells?
78

Dog heart cells are somatic, so they have 78 chromosomes.

Module 14 : Counting Chromosomes

In goldfish, 2n = 104. How many chromosomes are in a goldfish egg?
52

In diploid goldfish cells, there are 104 chromosomes. There are half this many chromosomes (or 52) in haploid cells.

Module 14 : Counting Chromosomes

Remember that in goldfish, 2n = 104. How many chromosomes are in a goldfish germ cell?
104

This is the diploid number. Eggs are gametes and must be haploid, but the cell that gives rise to the gametes is diploid.

Module 14 : Counting Chromosomes

Module 14 : Overview of the Cell Cycle
Relate the phases of the cell cycle to the corresponding cellular events.
Cell
The smallest fundamental unit of structure and function in life. Cells are fluid-filled spaces bound by a membrane. When first formed, all cells include DNA and other macromolecules and are organized to grow, reproduce, and respond to changes in the external environment.

Module 14 : Overview of the Cell Cycle

cell cycle
The “life cycle” of a cell. It is the set of stages that a cell goes through during its lifetime. Cells go through five major stages of development: G1, synthesis (S), G2, mitosis (M), and cytokinesis.

Module 14 : Overview of the Cell Cycle

interphase
The events that occur during stages G1, S, and G2. Nearly the same in all types of cells.

Module 14 : Overview of the Cell Cycle

parent cell
Like a human parent, it reproduces—it makes new cells that are copies of itself. The parent cell goes through the five stages of development in this order — G1, S, G2, M, and cytokinesis.

Module 14 : Overview of the Cell Cycle

daughter cells
the newly produced cells from a parent cell.

Module 14 : Overview of the Cell Cycle

n which phase of the cell cycle does DNA replication take place?
S

Module 14 : Overview of the Cell Cycle

Interphase is the part of the cell cycle when the cell: _____________________
Grows and duplicates its DNA

The cells grows in G1, duplicates its DNA in S, and makes final preparations in G2.

Module 14 : Overview of the Cell Cycle

In which stage of the cell cycle are new daughter cells formed?
Cytokinesis

During cytokinesis the cytoplasm and membrane of the parental cell is split in order to form two daughter cells.

Module 14 : Overview of the Cell Cycle

In which stage of the cell cycle would you expect the growing of the cell to occur?
G1

During G1, the cell is growing (amassing nutrients and making the preparations for the remainder of the cell cycle) and the chromosomes condense in preparation for DNA synthesis and mitosis.

Module 14 : Overview of the Cell Cycle

In which stage of the cell cycle would checking for DNA integrity occur?
G2

During G2, the integrity of the newly replicated DNA is checked. If there were errors in the replication of the DNA, the new daughter cells could be defective and harmful to the organism. Therefore, the quality of the DNA is inspected during the G2 phase to ensure that each daughter cell is getting a good copy of the DNA.

Module 14 : Overview of the Cell Cycle

Module 14 : Preparing for Cell Replication
Identify the chromatids and centromere of a chromosome and describe their role in cell replication.
Centromeres connect how many chromatids?
2

Each centromere connects two sister chromatids (one is the original and the other is the copy made during DNA replication).

Module 14 : Preparing for Cell Replication

Somatic cells
The nonreproductive cells. Somatic cells are diploid and reproduce using mitosis. Diploid cells (2N) have two copies of each chromosome.

Module 14: Cells & Chromosomes (Summary)

Germ cells
Immature reproductive cells. Germ cells are diploid and divide using meiosis to produce gametes. Gametes are haploid reproductive cells (sperm and eggs). Haploid cells (1N) have one copy of each chromosome.

Module 14: Cells & Chromosomes (Summary)

Cell division (mitosis and meiosis)
Sorts the genetic material (DNA) of a cell. This sorting of genetic material is essential, because most of the essential information for life is stored in the DNA. Each newly formed daughter cell must receive identical information; therefore the DNA in a cell must be copied before cell division begins. The copied DNA strands remain attached near their centers in a region called the centromere. Each copy of the DNA is called a chromatid, and both copies are called a chromosome. The cell packages the DNA so that it can be sorted between the new cells. The DNA is packaged by wrapping it tightly around proteins called histones.

Module 14: Cells & Chromosomes (Summary)

diploid cells
Referring to cells that contain two sets of chromosomes (i.e. pairs of homologous chromosomes). One set of chromosomes is inherited from the mother and the other set is inherited from the father. Diploid cells are 2n. Somatic and germ cells are diploid.

Module 14: Cells & Chromosomes (Summary)

Gamete
A haploid, sex cell (egg or sperm) produced from germ cells that have undergone meiosis. When two gametes join in fertilization the resulting zygote is a complete diploid cell.

Module 14: Cells & Chromosomes (Summary)

Gene
A segment of DNA that carries specific information, ultimately coding for a protein, which determines certain traits in an organism. The gene is the basic unit of inheritance. It is a segment of DNA with instructions for protein synthesis. Genes are located on DNA stands, and each gene is composed of a specific nucleotide sequence that codes for the amino acid sequence of a protein.

Module 14: Cells & Chromosomes (Summary)

Germ Cell
A cell that in the body of a sexually reproducing organism that produces gametes (eggs or sperm) through meiosis. Germ cells are immature reproductive cells. In humans, germ cells are found in the testes of men and ovaries of women.

Module 14: Cells & Chromosomes (Summary)

Haploid
Cells that contain only one set of chromosomes. Haploid cells are referred to as “1n”. Gametes (sperm and eggs) are haploid. In human haploid gametes contain 23 chromosomes.

Module 14: Cells & Chromosomes (Summary)

Homologous
Refers to two chromosomes that are a matched pair in a diploid cell. A matched pair of chromosomes are the same length and contain genes for the same characteristics at the same position on them. For each homologous pair, one chromosome is inherited from the mother and the other is inherited from the father.

Module 14: Cells & Chromosomes (Summary)

Homologue
Refers to one of the other of a homologous pair of chromosomes. Each is considered the homologue of the other.

Module 14: Cells & Chromosomes (Summary)

Karyotype
Diagrammatic representation of an organism’s genome. An image of the chromosomes of a cell in metaphase where the chromosomes are arranged in pairs by centromere position and size. Karyotypes are used to count and analyze the chromosomes of an individual and can also be used in the determination of chromosomal abnormalities.

Module 14: Cells & Chromosomes (Summary)

Meiosis
A type of cell division in which a single, diploid germ cell is divided into four, haploid gamete cells. Meiosis only occurs in organisms that sexually reproduce and results in the production of sperm in males and eggs in females.

Module 14: Cells & Chromosomes (Summary)

Mitosis
A type of cellular division in which a single, diploid, somatic cell is divided into two genetically identical daughter cells. Mitosis along with cytokinesis compose the mitotic (M) phase of the cell cycle.

Module 14: Cells & Chromosomes (Summary)

Sister Chromatid
One of two identical copies of a chromosome duplicated during the S phase of the cell cycle. A centromere connects two sister chromatids together. When joined together sister chromatids compose one chromosome, and chromatids are separated from each other during mitosis or meiosis.

Module 14: Cells & Chromosomes (Summary)

Somatic Cell
Any nonreproductive cell found in multicellular organisms. That is, any cell except a germ cell or gametes (sperm and egg cells) found in a muticellular organism. Examples are lung and heart cells, nerve cells, and blood cells.

Module 14: Cells & Chromosomes (Summary)

Zygote
The newly formed diploid cell that is produced when two haploid gametes unite. In animals this occurs when a sperm fertilizes an egg.

Module 14: Cells & Chromosomes (Summary)

During what stage of the cell cycle does the cell grow and carry out it regular functions?
G1

Cells and Chromosomes Quiz

A muscle cell is an example of what type of cell?
Somatic
If a cell is not dividing, and has not yet begun replicating its DNA what phase of the cell cycle would it be in?
G1 occurs before DNA replication (S).
The products of MITOSIS are:
Two genetically identical cells
All of the following pairings between a cell cycle phase and what happens during it are correct, except:

(A) G2- the cell is preparing to divide
(B) M- the cell is undergoing mitosis
(C) G0- the cell is mature and does not cycle anymore.
(D) S- the cell is dividing
(E) G1- the cell is growing and increasing its mass

S- the cell is dividing

Before the cell divides it has to copy its DNA, which happens during the S-phase of the interphase.

If a germ cell has 20 chromosomes, how many chromosomes will you find in the daughter cells, after meiosis?
10

Germ cells divide by meiosis, which results in 4 unique daughter cells, each with half the original number of chromosomes.

During the S phase of the cell cycle, DNA is replicated. What form would you expect the DNA to be in?
It would be in a loose pile

DNA in chromatin form is easiest to replicate.

A sperm cell is an example of:
A gamete

A gamete is a reproductive cell (sperm and eggs).

DNA that is tightly wound around histone proteins is the easiest to divide. Is this statement true or false?
True

When the DNA is tightly wound around histone proteins, it is easy to make sure one copy of each chromosome gets into the daughter cells.

Somatic cells are reproduced during the process of _____________:
Mitosis
Module 15: What Is Mitosis?
Describe the function of mitosis.

Match a picture of a cell with the stage of mitosis it is in.

Growing from a single fertilized egg to an adult organism requires many rounds of:
Cell division

Module 15: What Is Mitosis?

DNA replication occurs in the ________ stage of the cell cycle just prior to mitosis
synthesis (S)

Module 15: What Is Mitosis?

Prophase and Prometaphase
The cell prepares to sort the chromosomes.

Module 15: What Is Mitosis?

Metaphase
Chromosomes are moved to the center of the cell.

Module 15: What Is Mitosis?

Anaphase
Chromosomes are sorted

Module 15: What Is Mitosis?

Telophase
The new nuclei are formed.

Module 15: What Is Mitosis?

Each new cell gets one of these nuclei during the process of _______.
cytokinesis

Module 15: What Is Mitosis?

What role does mitosis play in the overall cell cycle?
Mitosis is the process of dividing a parent cell into two genetically identical daughter cells. DNA in the nucleus, which contains the genetic information, is first duplicated and condensed into tightly packed hread-like structures called chromosomes. During the four phases of mitosis, the nucleus is separated and divided into two identical daughter nuclei. Each daughter nuclei contains the same genetic material as the parental cell.

Module 15: What Is Mitosis?

Centrosomes
Used to identify the poles of the cell during the division process; these poles determine where the chromosomes will be sent.

Module 15: What Is Mitosis?

Module 15: The Phases of Mitosis
List the stages of mitosis and describe what happens at each stage.

Match a picture of a cell with the stage of mitosis it is in.

Explain what happens to the cell during the prophase of cell division.
The membrane around the nucleus disintegrates. DNA condenses into chromosomes, then splits into double-stranded chromatids.

Module 15: The Phases of Mitosis

Prometaphase
The stage between prophase and metaphase. he nuclear envelope is fully broken down. This allows the microtubules to attach to the centromeres of the chromosomes.

Module 15: The Phases of Mitosis

What structure moves the chromosomes to the correct location for cell division?
The microtubules

They attach the chromosomes to the centrioles. As the microtubules extend, they form spindle-like structures that push the centrosomes to opposite poles of the cell.

Module 15: The Phases of Mitosis

What is the significance of the name “Metaphase”?
Metaphase is so named because the chromosomes line up in the middle of the cell. The root “meta-” means “middle.”

Module 15: The Phases of Mitosis

Which structures are used to line up the chromosomes during metaphase?
During metaphase, microtubules attached to the centromeres line up the chromosomes down the middle of the cell. Remember that the centromere connects two sister chromatids each with the same genetic information.

Module 15: The Phases of Mitosis

What is the significance of the name “Anaphase”?
The root “ana-” refers to “apart”; the chromosomes are moving apart from each other.

Module 15: The Phases of Mitosis

How are kinetochore and nonkinetochore microtubules defined?
Kinetochore microtubules are attached to the kinetochore proteins on the centromere of the chromosome.

Module 15: The Phases of Mitosis

What is the significance of the name “Telophase”?
“Telo” comes from the Greek word for “end.”

Module 15: The Phases of Mitosis

How many cells are there at the end of telophase?
The cell now has two nuclei, but they have not been split into separate cells yet.

Module 15: The Phases of Mitosis

What is correct sequence of mitotic phases?
Mitosis starts by replicating DNA in the interphase. The nucleus disappears during the prophase and prometaphase, and then chromosomes line up in the middle of the cell during metaphase.

Module 15: The Phases of Mitosis

Module 15: Mitosis – Process Review
Predict the number of genes/gene pairs of the progeny cells based on the number of genes of the parental cell.

List the stages of mitosis and describe what happens at each stage.

Given that dogs have 39 pairs of chromosomes, how many total chromosomes can be found in a skin cell of a dog?
78

The total number of chromosomes is two times the number of pairs (2 x 39) because there are two copies of each chromosome.

Module 15: Mitosis – Process Review

How many pairs of chromosomes will be found in each daughter canine skin cell after mitosis occurs?
Each daughter cell will have 39 pairs of chromosomes, just like the parental cell.

Module 15: Mitosis – Process Review

You are studying mitosis in dog skin cells. You observe a cell under a microscope that contains two sets of 39 chromosome pairs located on opposite sides of the cell. You also note that it looks like nuclear envelopes are beginning to form around the chromosomes at each side of the cell. The cell you observed is in which stage of mitosis?
In telophase, the daughter chromosomes have been pulled to opposite poles of the cell (which happened in anaphase), and a new nuclear envelope forms around each group of chromosomes.

Module 15: Mitosis – Process Review

Module 15: Application Spotlight – Cancer
Relate the regulation of the cell cycle to cancer.
Tumor Suppressor Genes
Genes that inhibit cell division

Module 15: Application Spotlight – Cancer

Proto-oncogenes
Genes that encourage cell division. If these genes are working properly, a cell will not receive the message to divide unless it should be dividing.

Module 15: Application Spotlight – Cancer

Mutations
Errors in DNA that can result from genetic predisposition or environmental factors.

Module 15: Application Spotlight – Cancer

Mutagens
Chemicals in the environment that produce mutations

Module 15: Application Spotlight – Cancer

Carcinogens
Specifically those mutagens that have shown that they can cause cancer. Cigarettes, for example, contain carcinogens that can alter the DNA and disrupt proper regulation of the cell cycle.

Module 15: Application Spotlight – Cancer

The development of cancer requires mutations in BOTH
(1) proto-oncogenes and (2) tumor suppressor genes

Module 15: Application Spotlight – Cancer

oncogene
A malfunctioning porto-oncogene that promotes the development of cancer. The root “proto-” refers to “before” and the root “onco-” refers to “cancer.”

A defective tumor suppressor gene can no longer suppress tumors. Cancer is the result of numerous mutations in multiple genes involved in regulating the cell cycle.

Module 15: Application Spotlight – Cancer

Which function most closely describes how BOTH tumor suppressor genes and porto-oncogenes work?
They regulate the cell.

While both genes have different functions, they both affect cell division by regulating the cell cycle.

Module 15: Application Spotlight – Cancer

Module 15: Mitosis – Summary
Mitosis is the process by which eukaryotic cells divide into two identical daughter cells. The process ensures identical DNA is present in both daughter cells. Organisms use mitosis to grow and replace old or malfunctioning cells. There are checkpoints during the cell cycle that regulate whether or not a cell goes through mitosis. When this regulation goes awry, cells can begin to divide uncontrollably, possibly resulting in cancerous tumors.

Mitosis results in identical daughter cells. However, sexually-reproducing organisms need a way to produce gametes, which are unique haploid cells that combine to form new organisms. In the next module, you’ll learn more about meiosis, which is the process used to produce gametes.

Allele
An alternative form of a gene. An example would be genes that encode eye color – some encode blue eyes (one allele), while others encode brown, green or hazel eye colors (other alleles).

Module 15: Mitosis – Summary

Interphase
The stage of the cell cycle when division (mitosis) does not occur. During interphase, the cell grows, acquires nutrients, and replicates both its chromosomes as well as its organelles. Interphase consists of the G1 (chromosomes condense), S (DNA duplicates), and G2 (DNA integritiy checked and repaired) phases of the cell cycle. Cells spend the majority of their time in interphase.

Module 15: Mitosis – Summary

Prophase
This is the first stage of mitosis. In prophase, the nucleus is broken down, the chromosomes (duplicated during the S phase of the cell cycle) condense, and the mitotic spindles form.

Module 15: Mitosis – Summary

Anaphase
A stage within the mitosis phase of cell division (also known as cell reproduction). Anaphase starts when sister chromatids separate from each other and ends when each set of separated, sister chromatids arrives at the opposite poles of the cell.

Module 15: Mitosis – Summary

Kinetochore
Proteins on the centromere where microtubules attach. These attached microtubules are called kinetochore microtubules.

Module 15: Mitosis – Summary

Telophase
This is the final stage of mitosis. In telophase, new nuclear envelopes form around the separated chromosomes at each pole of the cell, the chromosomes unfold back into chromatin, nucleoli reappear, and the cell continues to elongate.

Module 15: Mitosis – Summary

Centrioles
The place where the microtubules originate from during mitosis. Centrioles are contained within the centrosomes.

Module 15: Mitosis – Summary

Metaphase
This is a stage of mitosis where the sister chromatids connected by centromeres are lined up along the plane of the cell’s center (called the metaphase plate).

Module 15: Mitosis – Summary

Cytokinesis
The division of the cytoplasm of a cell at the end of mitosis to form two separate daughter cells. In animals cells, this occurs through the pinching of the membrane at the center of the parental cell while in plants, this occurs through the formation of a cell plate as new cell wall forms to separate the daughter cells.

Module 15: Mitosis – Summary

Microtubules
One type of fiber that makes up the cytoskeleton of a eukaryotic cell. Microtubules consist of proteins called tubulins. Microtubules aide in cell structure and movement and are also responsible for moving the chromosomes during mitosis and meiosis.

Module 15: Mitosis – Summary

Which of the following tasks is accomplished through the process of mitosis?

(A) Production of sperm or eggs
(B) Replacement of dysfunctional cells
(C) Cell growth

(B) Replacement of dysfunctional cells

Mitosis Quiz

The centrosome disappears and the nuclear envelopes form in what stage of mitosis?
Telophase

Mitosis Quiz

An organism grows through what process?
Mitosis is cell division that results in growth.

Mitosis Quiz

In what stage are sister chromatids separated and pulled to opposite sides of the cell?
anaphase
Module 16: Meiosis – Asexual and Sexual Reproduction
Describe the function of meiosis as it relates to sexual reproduction.

Compare and contrast mitosis and meiosis in regards to their overall functions, steps of the processes, number of progeny cells, and number of genes (haploid vs. diploid).

Asexual Reproduction
All of the genes in a cell are passed to its daughter cells. This means that the resulting cells are clones, or identical copies of the parental cell.

Module 16: Meiosis – Asexual and Sexual Reproduction

What is the name of the process of asexual cell division that results in daughter cells that are identical to the parent cell?
Mitosis

Module 16: Meiosis – Asexual and Sexual Reproduction

What is the name of the process of sexual cell division that results in daughter cells that are NOT identical to their parent cell?
Meiosis

Module 16: Meiosis – Asexual and Sexual Reproduction

Chromatin
The combination of DNA and histone proteins

Module 16: Meiosis – Asexual and Sexual Reproduction

Sex chromosomes
Can be of two types: X and Y. Males have one X and one Y chromosome (XY), while women have two copies of the X chromosome (XX).

Module 16: Meiosis – Asexual and Sexual Reproduction

Fertilization
In sexual reproduction, two reproductive cells called gametes fuse in this process

Module 16: Meiosis – Asexual and Sexual Reproduction

diploid zygote
Haploid gametes produced during meiosis fuse to form a diploid zygote, which goes through the process of mitosis to grow into an adult human. When the adult human produces haploid gametes, the process can be repeated.

Module 16: Meiosis – Asexual and Sexual Reproduction

The main advantage of sexual reproduction compared to asexual reproduction is that it produces:
Sexual reproduction increases the genetic variation of the offspring.

Module 16: Meiosis – Asexual and Sexual Reproduction

Module 16 : Meiosis I
(1) List the stages of meiosis and describe what happens at each stage.

(2) Describe the function of meiosis as it relates to sexual reproduction.

(3) Predict the number of genes/gene pairs of the progeny cells based on the number of genes of the parental cell.

(4) Compare and contrast mitosis and meiosis in regards to their overall functions, steps of the processes, number of progeny cells, and number of genes (haploid vs. diploid).

Meiosis I
The reduction division. It is during this stage that the number of chromosomes in the parent cell are divided in half because homologous chromosomes are separated. One homologue with its sister chromatid go to one daughter cell while the other homologue with its sister chromatid go to the other daughter cell.

Module 16 : Meiosis I

Meiosis II
Extremely similar to mitosis, except that there are half as many chromosomes. In Meiosis II, sister chromatids are separated from each other.

Module 16 : Meiosis I

crossing over
Crossing over is responsible for generating much of the diversity that exists within a species. Remember that diversity in a species is one of the hallmark characteristics of living organisms.

A process in which genes swap positions on matching chromosomes. The result is a new combination of genes on each chromosome.

Module 16 : Meiosis I

metaphase I
Homologous pairs of chromosomes line up on the metaphase plate. This is very different from mitosis, when sister chromatids line up, completely independent of their homologues.

Module 16 : Meiosis I

anaphase I
Homologous pairs are pulled apart, and they move toward the poles of the cell.

Module 16 : Meiosis I

telophase I
Cytokinesis occurs and two new daughter cells are formed. Meiosis I ends with the production of two haploid daughter cells because the homologous pairs of chromosomes have been separated.

Module 16 : Meiosis I

Module 16: Meiosis II
(1) List the stages of meiosis and describe what happens at each stage.

(2) Describe the function of meiosis as it relates to sexual reproduction.

(3) Predict the number of genes/gene pairs of the progeny cells based on the number of genes of the parental cell.

Meiosis II
Begins with two haploid cells, each containing too much DNA. Remember that while homologous pairs of chromosomes were separated in Meiosis I, each homologous chromosome is still connected to its sister chromatid.

Module 16: Meiosis II

At the end of telophase II, the number of chromosomes is
1N (haploid)

Module 16: Meiosis II

In which stage of meiosis are sister chromatids separated?
Sister chromatids are separated during anaphase II of meiosis.

Module 16: Meiosis II

Module 16: Application Spotlight – Aneuploidy
Explain how an incorrect separation of homologues or sister chromatids can result in defective gametes.
nondisjunction
The unequal separation of homologous chromosomes results in cells with more or less chromosomes than normal.
Module 16: Meiosis: Summary
Meiosis is a process of reductive cell division that produces haploid (1N) cells from diploid (2N) cells. In animals, gametes are haploid reproductive cells that are produced using the process of meiosis. The gametes from two individuals fuse in the processes of fertilization to produce a diploid zygote. The diploid zygote divides using the process of mitosis to become an adult organism.

Meiosis is divided into two phases. In meiosis I, homologous pairs of chromosomes bind together and exchange pieces. This process is called “crossing over” and is essential for generating diversity within a species. By the end of meiosis I the homologous pairs of chromosomes have been sorted into separate cells. In meiosis II, the individual chromatids of a chromosome are sorted into separate cells. By the end of meiosis, a single diploid cell has divided into four haploid cells.

Asexual Reproduction
A type of reproduction where genetically identical offspring are created from a single parent. This type of reproduction does not utilize meiosis or gametes. Bacteria and fungi are examples of organisms that reproduce in this manner.

Module 16: Meiosis: Summary

Nondisjunction
The failure of sister chromatids or homologous chromosomes to separate during anaphase of either mitosis or meiosis.

Module 16: Meiosis: Summary

Clones
The genetically identical offspring produced from asexual reproduction

Module 16: Meiosis: Summary

Sexual Reproduction
A more complicated form of reproduction where two haploid, gametes (sperm and egg) fuse to create a diploid zygote. This type of reproduction produces offspring that are genetically different from their parents.

Module 16: Meiosis: Summary

Karyotype
Diagrammatic representation of an organism’s genome. An image of the chromosomes of a cell in metaphase where the chromosomes are arranged in pairs by centromere position and size. Karyotypes are used to count and analyze the chromosomes of an individual and can also be used in the determination of chromosomal abnormalities.

Module 16: Meiosis: Summary

Meiosis II
The second half of the whole process of meiosis in which the sister chromatids in each of the two haploid cells produced during meiosis I are separated. Meiosis II results in the production of four haploid gamate cells and is similar in process to mitosis.

Module 16: Meiosis: Summary

What advantage does sexual reproduction have over asexual reproduction?
Sexual reproduction provides more genetic variability.

Asexual reproduction produces identical copies (unless a mutation occurs); sexual reproduction produces variability.

Module 16: Meiosis Quiz

Mitosis results in ________ and meiosis results in ________.
somatic cells, gametes

Module 16: Meiosis Quiz

Cats have a diploid number of 38. How many chromosomes are in a cat egg?
19

Haploid cells have half the number of chromosomes as diploid cells.

Module 16: Meiosis Quiz

Mitosis results in ______ cells and meiosis results in _______ cells.
diploid, haploid

Module 16: Meiosis Quiz

Crossing over occurs between homologous chromosomes during what stage of cell division?
Prophase I of meiosis

Module 16: Meiosis Quiz

Homologous chromosomes separate and are pulled to opposite sides of the cell during what stage of cell division?
Homologous chromosomes are separated and pulled to opposite sides of the cell during Anaphase I.

Module 16: Meiosis Quiz

Which of the following tasks is accomplished through the process of meiosis?
Meiosis results in sperm or egg production.

Module 16: Meiosis Quiz

Imagine a hypothetical organism (critter). A DIPLOID cell from this organism has 40 chromosomes. How many chromosomes would be found in a HAPLOID GAMETE of this organism?
20
If a somatic cell has 46 chromosomes, how many chromosomes will you find in the daughter cells, after mitosis?
46
Which structure connects two sister chromatids?
The centromere is where two sister chromatids attach.
Which stage of the cell cycle is NOT part of interphase?
M (Mitosis or Meiosis)

Mitosis and meiosis are nuclear division.

A muscle cell would divide to make more muscle cells using the process of:
Mitosis
During which stage of the cell cycle are cell organelles (like mitochondria, lysosomes, ribosomes) DIVIDED into two new cells?
Cytokinesis
DNA that is loosely wound is the easiest to replicate. Is this statement true or false?
True

If the DNA is loosely wound, molecular enzymes have easy access the molecule to make a copy.

Chromosomes align on the equator of the cell during…
Metaphase
An organism produces gametes through what process?
Meiosis
rue or false: DNA that is loosely wound is the easiest to divide.
False

If DNA is in a loose pile, it is difficult to make sure a complete copy goes into each daughter cell.

A sperm has 16 chromosomes. How many chromosomes were in the germ cell that gave rise to the sperm?
32
Gametes are supposed to be haploid. Complete the sentence: If nondisjunction occurs,
Two answers are correct: the gamete could be diploid, or it could be missing a chromosome entirely.