This Chapter will include both Genetics and Infectious Disease.  We have studied the human body from the perspective of "what is Healthy or Normal".  Normal health is that state of health that allows the organism to successfully grow and develop through the life stages and REPRODUCE.  Remember those Characteristics of Life?  Living things reproduce themselves.  These activities require energy (the organic molecules) and nutrients (water, minerals, vitamins).  We have defined 'health' as homeostasis.

Homeostasis is the existence and maintenance of a relatively constant internal fluid environment, pH environment, and electrolyte environment.  Each of these has a set point.  The perfect set point allows the organism to use energy and nutrients with the greatest efficiency in his specific environment.  This means that the organism achieves 100% healthy growth and development using the least amount of energy - the organism lives within his world, impacted by food availability, predators, energy demands, injury and repair, etc - all those activities required for a 'living being'.  The organism successfully maintains 'living being' all while using the least amount of energy and nutrients to remain 'living'.  This means therefore that the energy and nutrients in excess of that amount needed to maintain 'living' can be used for other things - such as reproduction.  Whenever resources are limited, the body does not have enough resources to maintain perfect health, the internal environment moves away from one or more of the normal, healthy set points.

Maintaining that relatively constant internal environment .... away from the average set point leads to disease...  there are two ways to leave the set point - genetic and infectious

So... maintaining a set point requires resources.  Stress is any condition that pulls the body away from normal, healthy homeostasis. Remaining for a prolonged period away from the normal 'healthy' set point results in a lack of growth, damaged tissues do not get repaired - scar tissue forms or are replaced with cells that do not function as efficiently - i.e. the body loses some resource use efficiency, and it becomes 'diseased'.

Disease is that condition where the body has moved away from the 'perfect' set point where the body is in tune with its external conditions and is using resources most efficiently, to a set point where the body is struggling just to stay alive, let alone repair itself or reproduce.

How do genes cause disease?

Genes produce proteins (especially enzymes) that dictate the efficiency with which the body uses resources.  Each protein has a specific function and the integration of all those functions determines how efficiently the body uses resources.  Enzymes are proteins that control and regulate metabolism. Metabolism is all the chemical reactions that the body uses to acquire energy and nutrients available and then use the energy and resources to maintain the particular set points.  Genes that produce proteins that cannot maintain a set point that allows the organism to use energy and nutrients efficiently produce an individual that is not a 'fit' to the world in which it must live - i.e. able to access those resources in sufficient quantity for growth, development, and reproduction.

How does protein shape determine 'disease'?
      Review Chapter 2, Proteins
How does DNA determine the shape of the protein?
     Review protein synthesis in Chapter 3, Cells.

First, we will study genes and how they function, and some genetic diseases caused by genes that malfunction.

Chromosomes – the cell organelle/structure that contains the DNA molecule. 
There are 23 pair of chromosomes in the normal human cell.  One chromosome of each pair came from the mother, one chromosome from the father.  I.e. there are 23 pair of chromosomes - chromosome #1 is made up of 2 chromosomes: one from mom, one from dad.  Chromosome #2 is made up of one from mom, one from dad.  #3= one from mom, one from dad...  and so on.   The chromosome from the mom in #1 is homologous to the chromosome from the dad in #1.  The chromosome form the mom in #2 is homologous to the chromosome from the dad in #2. 

Define meiosis, mitosis

Homologous chromosomes– the two chromosomes that make up a pair of chromosomes. 
   Remember: Homo = SAME
      Now, why are the two chromosomes that make up a pair called 'homologous'?

Each chromosome in a pair, contains the SAME genes.  For example, if chromosome #1 from dad contains the gene for eye color, then chromosome #1 from mom will also contain the gene for eye color.  Homo = same; -logous = loci or position. Homologous = same gene in same location.
           Look at the diagram of 'paired' chromosomes in the text:
                      Karyogram, OR, Map of Human Chromosomes.
           Note the 'bands' on each pair, and that each 'band' has a 'twin' on the homolog.
              Each 'band' is a gene - note that SAME gene has its counterpart in the SAME location
              on each chromosome.
                     Homolog - same gene in same location.

Which chromosomes are homologous in #17?
   Chromosome #17 from Dad is homologous to chromosome #17 from Mom.

Autosomes – all the non sex chromosomes – humans have 22 pair of autosomes
  aka - Autosomal chromosomes

Sex chromosomes- the chromosomes that determine gender. Humans have 1 pair of sex chromosomes.

Where is the chromosome located?
    What is a chromosome?
       How many pairs of chromosomes do humans have?
         How many TOTAL chromosomes do humans have?
             2 X 23 = 46
Where do we get our chromosomes?

Gene – the segment of a DNA molecule that codes for a specific protein.

Allele- the different (various) forms of a single gene:
       Eye color – blue, brown and green. There are 3 alleles for eye color.
       Hair color – black, blond, brown, red.
            How many alleles are there for hair color?

Homozygous – both alleles for a gene are the same.  I.e. an individual has eye color genes from both mom and dad that give him blue eyes. 

-zygous = zygote

Heterozygous – the alleles for a gene are different – one blue eye gene from one parent, one brown eye gene from the other parent.

Genotype – the actual genetic makeup  - Homozygous or heterozygous.

Phenotype – the physical appearance of the individual – it is dictated by the genotype and modified by the environment in which the individual lives.  A person with a blue eye allele and a brown eye allele will have BROWN eyes. Phenotype is what you see.  

How does 'environment' affect the phenotype?
  A person with TALL gene, will only be as tall as his nutrition allows.

A dominant allele is dominant over a recessive allele. Brown eye allele is dominant over blue eye allele. A person with a genotype that is heterozygous for eye color, with a brown eye allele and a blue eye allele will have brown eyes as the phenotype.

Disease caused by a defective gene.
Disease caused by a gene that malfunctions. The Gene is the ‘control center’ of a DNA molecule – your genes determine your physical appearance and the exact homeostasis that you maintain. Your genes are part of your normal cells.

What is the function of a gene?
    Review chapter 3 – protein synthesis.

What does a gene code for?
A specific protein. We need that protein to do its job – its specific function. If it is nonfunctional, then we get a ‘disease’.

What is a mutation?
  A mutation is a change in the sequence of nucleotides in a gene.  This can be a loss of 1 or more nucleotides, the addition of 1 or more nucleotides, or a substitution of nucleotides.  If you change the order of the nucleotides, it may very well produce a different sequence of amino acids and therefore a protein that is NONfunctional.

Or a protein with a different function - i.e. eye color, hair color. 

Down syndrome
Turners syndrome
Klinefelters syndrome

Color blind
Hemophilia
Muscular dystrophy

Marfan’s syndrome
Cystic fibrosis

What is a mutagen?
What is a teratogen?
What is a carcinogen?
How do these ‘cause’ disease?

NOW- we will contrast genetic disease with INFECTIOUS disease.

Infectious disease is caused by pathogens that are able to move from one person (host) to another.

Pathogens are organisms that are NOT related to humans. They are ‘foreign’ organisms.
 How is this different from genes?

Pathogens are actually pirates who steal from us those resources we have acquired, and therefore cause disease.  Again, the body does not have sufficient energy and resources to maintain perfect health and excess resources for reproduction.

Since the body cannot maintain perfect health (most efficient resource use) then the damaged or dead tissues are not repaired or replaced. 

Pathogens cause disease in two ways. 
   1. We have acquired some resources, energy and nutrients, and the pathogen takes them away
       from us.  These resources are no longer available to use for growth and development, and
       there certainly are no 'excess' available for reproduction.
   2. We have acquired and used some resources to grow our own tissues.  Some pathogens move
       into the body and use the tissues that we have grown as a nutrient source for their own growth
        and development.
 

Microorganisms - most pathogens are microorganisms - cannot be seen with the naked eye.
Pathogens
     Bacteria - usually are located in the interstitial spaces (extracellular) when causing disease.
     Classified in two ways:
         Shape: 3 ways
             Rods – longer than thick
             Spheres – spherical; the cocci; Neisseria gonococcus
             Spiral - in a spiral shape; Syphilis

         Stain: with Gramm stain, if they stain they are Gramm positive; if not they are Gramm negative.

     Fungus/Yeast - usually located on an epithelial surface when causing disease.
     Virus  - usually located INSIDE a cell (intracellular) when causing disease.
     Nematodes - multicellular organisms that burrow through tissues and cause 'disease'.

Describe where each of the above is physically located when it is pathogenic.

Bacteria are in interstitial spaces

Fungus/Yeast – on the surfaces of membranes – usually external membranes.
     What are the external membranes? Review chapter 4, Tissues
        What are the characteristics of external membranes?
          List the external membranes

Symbiosis is two organisms living together – usually one on the other.

Mutualism is a symbiotic relationship in which both benefit.

There are over 400 species of microorganisms that live in and on the human body at all times. We NEED these microorganisms for homeostasis.

Review Chapter 16, Digestive System, Normal Flora.

Microbes are found on every external surface of the body. Remember, the lining of the gut is EXTERNAL to the body.

Parasitism is a symbiotic relationship in which one (the parasite) benefits and the other (the host) is harmed. Parasites use resources that WE have accessed for OUR use. When the parasite uses those resources, the resources are NOT available to us for our use!

A disease caused by a pathogen that is able to move from one 'host' to another.

In order to move from one host to another the pathogen must have a mode of moving: the vector.

Vector – the manner in which a pathogen is spread from one host to the next.

1. Wind or airborne. Flu in minute water droplets suspended in the air we breath.
2. Bodily fluids – STDs, some hepatitis
3. Food- contaminated with pathogens such as botulism, salmonella, fecal coliforms, mad cow, etc.
4. Waterborne - diphtheria, cholera, typhoid, etc
5. Insect borne - malaria, sleeping sickness, chaga's disease, lyme disease,
         rocky mountain spotted fever, West Nile Encephalitis, etc.

In the past, society connected cholera, typhoid, diphtheria to DRINKING WATER - today, we run our drinking water through a 'municipal' water treatment plant to KILL these pathogens, and most cities in the United States no longer have outbreaks of these 'waterborne' pathogens.

The AMA recommends the use condoms made of synthetic materials during sex to prevent sexually transmitted diseases.

The AMA recommends that folks ill with airborne pathogens such as the FLU or the common cold, voluntarily quarantine themselves at home, to prevent the spread of airborne pathogens.  Dust masks are also recommended to prevent the spread of airborne pathogens.

Define quarantine.

Insecticides have been widely used to prevent the spread of insect borne diseases.

Pasteurization is widely used to prevent the spread of food born diseases, and to keep food from 'spoiling'..
  aka - Tyndalization.  Heat the food to a specified temperature (usually above 150 F) for a specific period of time. 

A series of 3 times heating the food to boiling for 5 minutes, cool to room temperature and let sit for 30 minutes, then reheating, will kill most pathogens in the food.

The food can then be 'canned' and stored (canned goods), or sold (milk, cheese, so-called 'fresh' fruit juices, etc)

Asymptomatic - an individual that is 'carrying the disease causing agent' - and perhaps infectious - with showing the symptoms of the disease. A Famous example isTyphoid Mary,

Indescriminant and poorly supervised use of antibiotics has killed those members of a pathogenic species that were susceptible to the antibiotic, without killing those that were resistant. NOW, we have populations of pathogens that can infect humans and our medicines will not stop them.

What does this mean to YOU and your health?
  IF you get an infection with one of these pathogens, it is YOU and your immune system against the pathogen.  REMEMBER- these pathogens are resistant to antibiotics!

Why did I include TB in the above list?
TB was almost eradicated in the 1st world countries, but indiscriminant use of antibiotics in crowded populations has lead to a resurgence of TB that is now antibiotic resistant.  These crowded conditions occur in PRISONS -especially in Russia and the former USSR; and in third word countries with heavily used public transit systems (chicken buses, trains in India, etc)
 

Smallpox
Chickenpox
Measles
Mumps
Typhoid
Cholera
Diphtheria
Scarlet fever
Flu
Common cold
Rabies
Herpes
Some forms of hepatitis
Meningitis
UTI’s
PID

STDs  - what are STDs
  Syphilis
  Gonorrhea
  AIDS
  Chlamydia
   Herpes
  Genital warts
  UTI’s
   PID