DNA Structure, DNA Replication, Mitosis

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DNA Structure, DNA Replication, Mitosis Cancer
CP Biology
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DNA

• Holds the genetic information.
• DNA is inside every cell except for mature Red
  Blood Cells (RBCs).
• In humans, DNA is divided up into 46 pieces
  called chromosomes.
• Chromosomes are paired(23).
• Chromosomes are made up of thousands of genes.
• Genes are various sequences of DNA bases.

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DNA Shape Double Helix spiral staircase
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Watson, Crick Wilkins

• Discovered the structure of DNA in 1953.
• Won the Nobel Prize for this discovery in 1962.

http//www.youtube.com/watch?vsf0YXnAFBs8
FYI Rosalind Franklin was responsible for much
of the research and discovery work that led to
the understanding of the structure of DNA. She
died at the age of 37, four years before the
Nobel Prize was given. Many believe her name
should also be included in discovering the
structure of DNA since her X-ray diffraction
image was paramount for Watson Crick.
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• Steps of the ladder are made up of four bases
  also held together by hydrogen bonds.
• Sides of ladder are made up of alternating
  sugars and phosphates held together by a hydrogen
  bond.

A - T
G - C
S
P
S
P
S
P
S
P
S
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Chargaffs Rule One pyrimidine and one purine
match up to make one step of the DNA ladder.

• Adenine always pairs with Thymine.
• Guanine always pairs with Cytosine.

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• Bases only attach to
• another base
• sugar

Phosphates only attach to sugars
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Secret of Life Part 1

• http//www.youtube.com/watch?vunBlYYxMWjEfeature
  related
• 10 min.

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Do Now!

• 1. What structure holds genetic information?
• 2. What are the 4 bases?
• 3. What does phosphate attach on the DNA strand?
• 4. What sugar is found in DNA?
• 5. How many rings do purines have? ____
  Pyrimidines?___
• 6. Name the 2 purines and pyrimidines,
  respecitively.
• 7. To what two structures does sugar connect to
  in the DNA strand?

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DNA Replication

• Our DNA is split up into 46 chromosomes.
• Before a cell can divide, the DNA must first
  replicate. (46 ? 92)
• In that way, we keep the same amount of DNA in
  our cells after they divide into two cells.
• Our cells go through DNA replication right before
  they go through cell replication.

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Chromosome structure
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Copying the Code

• Each strand (of the double helix) has all the
  information needed to reconstruct the other half
  by the mechanism of base pairing.
• Because each strand can be used to make the other
  strand, the strands are said to be complementary.

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Step 1 DNA Replication

• A section of DNA unwinds and opens into a
  replication fork.

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Step 2 DNA Replication

• New nucleotides are added according to the base
  pairing rule (Chargaffs Rule) forming a new
  complimentary strand.

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Step 3 DNA Replication

• DNA Polymerase proofreads the new strand for
  mistakes and if a mistake is found, it can go
  back, remove the mistake, insert the correction,
  and continue on.

After proofreading, there may be only one mistake
every 1 billion nucleotides
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• During replication, DNA may be lost from the tips
  of chromosomes, which are called telomeres.

When the telomeres are all used up, a normal cell
will self-destruct thus preventing loss of any
valuable DNA from the exposed tips which could
lead to a mutation.
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Replication in Eukaryotic Cells

• Eukaryotic cells have much more DNA (all
  contained in chromosomes, which are in the
  nucleus)
• Replication begins at dozens or even hundreds of
  places on the DNA molecule, proceeding in both
  directions until each chromosome is completely
  copied.

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Replication in Prokaryotic Cells

• Most prokaryotes have a single, circular DNA
  molecule in the cytoplasm.
• Replication in most prokaryotic cells starts from
  a single point and proceeds in two directions
  until the entire chromosome is copied.

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DNA Replication

• http//youtube.com/watch?vLuw5_z8mIrIfeaturerel
  ated
• http//youtube.com/watch?vteV62zrm2P0featurerel
  ated

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• Now that the DNA has replicated, the cell is
  ready to divide.
• This step is called mitosis.

• www.synapses.co.uk/genetics/dnastruc.html

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Asexual vs. Sexual Reproduction

• Asexual Reprod. no mix of DNA all offspring are
  clones of the original.
• Sexual Reprod. genetic variation DNA from two
  individuals are mixed together.
• Sexual Reprod. Is an evolutionary advancement
  over asexual reproduction.

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Binary Fission
Ex. bacteria
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The Cell Cycle

• Interphase
• (G1, S, G2)
• Mitosis
• (prophase,
• metaphase,
• anaphase,
• telophase)
• Cytokinesis

cytokinesis
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Interphase

• Most cells spend a majority of their life in
  Interphase.

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• Interphase

• In G1 stage cell growth.
• S stage DNA replication occurs.
• The G2 all other organelles replicate.

G0 phase is the phase where the cell is just
hanging out. Its not growing it is an active
cell undergoing regular cell processes.
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What is Mitosis?

• Definition
• Mitosis is nuclear division plus cytoplasmic
  division, that produces two identical daughter
  cells.

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Mitosis is divided into 4 phases
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Prophase
Plant cell
Animal cell
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Metaphase
Animal cell
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Anaphase

• The paired chromosomes separate at the
  centromeres and move to opposite poles.

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Anaphase Continued
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Late Telophase in Animal Cells -a cleavage
furrow begins to form pinching the one cell
eventually into two cells.
Cleavage furrow
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Late Telophase In Plants -a cell plate
begins to form, eventually dividing the cells
into two cells.
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• Telophase marks the end of mitosis.
• The next phase is Cytokinesis the division of
  the cytoplasm.
• The two phases usually run together.

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Cytokinesis
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How long does this all take?
Time length varies depending on the type of cell.
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A Typical animal mitosis slide
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Typical Plant Cell
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Can you find all the phases in the plant mitosis
slide?
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Can you find all the phases in the plant mitosis
slide?
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Do Now! Name that phase

• 1. 5.
• 2. 6.
• 3.
• 7.
• 4.

8. What do plant cells create during telophase
that animal cells do not? 9. What do animal cells
create during telophase that plant cells do
not? 10. What mitotic structure is found in
animals but not in plants?
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Why Divide?

• As a cell becomes larger, its volume increases
  faster than its surface area.
• When a cell is too big there are more demands on
  the DNA
• Obtaining enough oxygen
• Obtaining nutrients
• Getting rid of waste
• A cell may die due to starvation or poisoning.

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Mitosis on YouTube

• http//www.youtube.com/watch?vVlN7K1-9QB0NR1

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Cancer
Mitosis gone wild
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What is cancer?

• What we think of as "cancer" is actually a group
  of more than one hundred separate diseases.
• These diseases are all characterized by an
  abnormal and unregulated growth of cells, in
  essence, mitosis gone wild
• This growth destroys surrounding body tissues and
  may spread to other parts of the body in a
  process that is known as metastasis.
• You cannot catch cancer from someone else.

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Cancer is.
FYI Cancer affects only multi-cellular organisms

• Unregulated cell growth
• Cells no longer respond to normal control
  mechanisms
• They no longer heed to normal signals that
  regulate cell cycle
• They do not stop dividing when growth factors are
  depleted.

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Checkpoints (p53)

• All cells have checkpoint controls where certain
  genes/proteins, such as p53 , help cells decide
  whether they should
• 1. repair damaged DNA (when this occurs, cells
  are said to be in CELL-CYCLE ARREST) or
• 2. commit cellular death (apoptosis).

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Checkpoints (p53) continued

• Mutation is a sudden change in the base pair
  sequence of DNA.
• Mutations to p53 result in damaged DNA being
  allowed to proceed through mitosis, passing on
  even more mutations.
• Half of all cancers involve mutations to p53

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Normal checkpoint sites
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1. Which diagram shows cancer cells? How do you
know?

• 2. Compare and Contrast Explain how cancer cells
  are different from normal cells. Then, relate
  these characteristics to the diagram above that
  shows cancer cells.
• 3. Predict Look at the cancer cells shown above.
  What can happen if these cells are left
  untreated?
• Apply Concepts Explain the role that p53 might
  have had in the growth and division of the cells
  shown in each diagram above.
• 5. Problem Solving How might the cancer cells
  shown in the illustration above be prevented from
  doing more harm to the organism they are a part
  of?

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Cancer

• When a cell repeatedly divides, a mass called a
  tumor forms.
• Tumors put pressure on surrounding cells and
  interfere with their function.
• Cancer cells may also break off of a tumor and
  spread throughout the body in a process called
  metastasis.

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Melanoma Dear 16 year old me http//www.youtube.
com/watch?v_4jgUcxMezM

• When these proto-oncogenes mutate and become
  oncogenes, they become capable of causing cancer.

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Tumors

• The tumor is fed by an independent blood supply
  to the tumor.

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Tumors can cause destruction in four common ways

• 1. Tumors put pressure on nearby tissues and/or
  organs.
• 2. Tumors invade tissues and organs directly
  (direct extension), often damaging or disabling
  them in the process.
• 3. Tumors make invaded tissues and/or organs
  susceptible to infection.
• 4. Tumors can also release substances that
  destroy tissues in close proximity to them.

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Lung tumor has invaded the soft tissue
surrounding it and has put pressure on other
organs.
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Tumors can be either malignant or benign.

• A malignant tumor is cancer, and a benign tumor
  is not.
• Benign tumor will not spread (metastasize).
• Benign tumor grow by enlarging rather than
  invading.
• Ex. Fat tumors
• A malignant tumor will eventually metastasize and
  invade all parts of the body (if left untreated).
  
• Dont look at following picture if youre
  squeamish.

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• Cancer cells metastasize throughout the body via
  the vascular system.

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• Cancer can develop anywhere in the body, and at
  any age.

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Carcinogen

• Is a cancer-causing agent

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What are the Causes and Risk Factors for Cancer?

• 1. Tobaccosmoking causes 30 of all cancer
  deaths in the U.S. and is responsible for 87 of
  cases of lung cancer.
• Quitting smoking immediately decreases your risk
  factor for cancer.

Girls who smoke 10 cigarettes per day or more are
at greatest risk, particularly for abdominal
obesity.
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What are the Causes Risk Factors for Cancer?

• 2. Environmental Factors
• Radiation
• Solar UV radiation
• X-rays
• power lines
• cell phones

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• 3. Air Pollution

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• 4. Water Pollutants Carcinogens such as
  chlorine by-products, industrial chemicals, heavy
  metals, pesticide residues, fluoride, arsenic,
  hormone-disrupting chemicals, coal-fired power
  wastes.

Pharmaceuticals Found in Drinking WaterAOL
3/9/08 AP Staff Posted on Sunday, March 09,
2008 71343 PM Pharmaceuticals including
antibiotics, anti-convulsants, mood stabilizers
and sex hormones have been found in the
drinking water supplies measured in quantities of
parts per billion or trillion, far below the
levels of a medical dose.
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• 5. Toxic Products
• Plastics
• Never freeze liquids in plastic then thaw out to
  drink/eat.
• Never microwave food in plastic containers.
  Plastic chemicals (dioxins) will leech into the
  food/drink.
• Dioxins can cause cancer.

Read about Personal Health http//chicagoconserva
tioncorps.org/blog/wp-content/uploads2/2008/08/L05
20Green20Guide20Print_20Plastic20Containers.p
df
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• 6. Natural Carcinogens
• Mold growth in damp areas like basements.
• Radon gas leaking into buildings

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• 7. Unsafe Sex
• Practicing unsafe sex can increase your risk of
  developing a virus called HPV (human papillioma
  virus.)
• HPV increases your risk factor for cervical,
  anal, vulvar and vaginal cancer.
• HPV is so common that at least 50 of sexually
  active men and women get it at some point in
  their lives.
• FYI there is now a controversial vaccine
  available to prevent getting HPV.

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FYI Cervarix and Gardasil.

• Gardasil is also licensed, safe, and effective
  for males ages 9 through 26 years for girls who
  are 11 or older .
• Several types of cancer are associated with HPV
• Cervical cancer The most common HPV-associated
  cancer. Almost all cervical cancer is caused by
  HPV.
• Vulvar cancer About 40 are linked to HPV.
• Vaginal cancer About 70 are linked to HPV.
• Penile cancer About 40 are linked to HPV.
• Anal cancer About 85 are linked to HPV.
• Cancers of the head and neck are mostly caused by
  tobacco and alcohol, but recent studies show that
  about 25 of mouth and 35 of throat cancers may
  be linked to HPV.

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• 8. Lifestyle and Diet Factors
• Diettoo much meat, not enough fruits and
  vegetables.
• Obesity, and lack of regular exercise.

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• 9. Other Food Factors
• 1. Processed food such as nitrosamines,
  aspartame, some food colorants.
• 2. Bovine growth hormone in milk. (this hormone
  makes the beef muscle bigger and then it is
  secreted in the cows milk)
• 3. Some salt-cured, pickled, and smoked food.
• 4. Alcohol consumption.
• 5. Food contaminated with pesticides and
  herbicides (not grown organically.)

RBGH in your milk http//vimeo.com/1221481
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• 10. Other Factors
• Exposure to toxic substances pre-conceptually, in
  utero, during infancy, during puberty.
• Family history of cancershared habits, shared
  pollution, shared genes.
• Poverty.
• Living near toxic sources.
• Genetic variabilitysome people are more
  vulnerable than others. (Braca 1)

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Treatments

• 1. Chemotherapy kills all fast replicating cells
• 2. Radiation locally kills cells
• 3. Surgery removes cells/tumor
• 4. Stem cell research may lead to cancer cures
  because stem cells can be turned into any kind of
  cells. (Section 10.4 Stem Cells)
• 5. News in cancer treatment Personalized
  medicine?
• http//www.cbsnews.com/video/watch/?id4580875n

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Tumor photos

• WARNING
• Not for the squeamish.

Neurofibromitosis Breast cancer Facial
tumors Skin cancer Tongue cancer Lip cancer
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NEUROFIBROMITOSIS benign
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Breast Cancer malignant
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Facial Tumors benign
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Skin cancer malignant
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Tongue cancer malignant
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Lip cancer from smoking
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• Most cancer is preventable.
• Take the time and effort to take care of
  yourself.
• Stay away from harmful environments, activities,
  and foods that are known to be carcinogens.
• Check yourself.
• Dont be embarrassed to seek help.
• Dont ignore a noticeable change in your body.
• Early detection could save your life.

Over the course of a lifetime, 1 in 8 women will
be diagnosed with breast cancer.
Testicular cancer is the most common cancer in
American males between the ages of 15 and 34 ( 1
in 270 people will get it)
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The End
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FYI

• Answers to some questions that I have been asked
  during this chapter.

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Asexual Reproduction

• Some organisms reproduce without the use of sex
  cells or a partner.

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Budding
Ex. Sponges,Yeast Hydra
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Vegetative Propagation
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Regeneration
Ex. Sea Star
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Spores

• Fungi and some algae can also utilize true
  asexual spore formation, which involves mitosis
  giving rise to reproductive cells called
  mitospores that develop into a new organism after
  dispersal. This method of reproduction is found
  for example in conidial fungi and the red alga

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(No Transcript)
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Parthenogenesis

• is an asexual form of reproduction found in
  females where growth and development of an embryo
  or seed occurs without fertilization by males.
  The offspring produced by parthenogenesis are
  always female in species where the XY chromosome
  system determines gender.

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(No Transcript)
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How are Twins created?

• Fraternal twins 2 eggs fertilized by two sperm.
• Identical Twins 1 egg fertilized by 1 sperm.
  The embryo splits with the first few days
  creating 2 identical people sharing 1 placenta.

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Whats a hermaphrodite?

• Hermaphrodites are divided into two main
  categories
• 1. Organisms that possess both active male and
  active female reproductive organs at the same
  time.
• 2. Both male and female reproductive organs may
  be present, but only one is active and viable at
  any given time.

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• Hermaphrodites are mostly found among
  invertebrates and plants, few fishes and rarely
  among the higher chordates.

Earthworms
Banana Slugs
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Plants have both male female parts in their
flowers.
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Sea bass
Hermaphroditic fish
Hamlets
In birds and mammals, hermaphroditism is usually
a pathological condition causing infertility.