Medical Terminology, Genetics, and Inheritance

Levels of Organization

• Understanding the structure and function of the body requires understanding its organization.
• There are five levels of organization, each increasing in complexity.
• The levels build upon each other.

Five Levels of Organization:

1. Cellular Level

   • Cells (cyt/o) are the smallest living units of structure and function.
   • Cells are the fundamental units of all living things.
   • Human beings contain about 200 different types of cells, each adapted to a different task.
   • Cell Structure:
     • Cell Membrane: Surrounds and protects the cell; regulates what passes into and out of the cell.
     • Nucleus: "The brains" of the cell; controls operations, directs cell division, and determines structure and function.

2. Tissue Level

   • A tissue (hist/o) is a group of cells with similar structure and function.
     • Epithelial Tissue:
     • Linings and outer surfaces.
     • Example: surface of the skin.
     • Muscle Tissue:
       • Muscles contract to provide movement.
       • Contractions can be voluntary or involuntary.
       • Voluntary Example: movement of arms and legs.
       • Involuntary Example: heartbeat.
     • Connective Tissue:
       • Joins other tissues together.
       • Examples: cartilage and adipose (fat).
     • Nerve Tissue:
       • Nerves conduct impulses.
       • Located throughout the body.

3. Organ Level

   • Groups of tissues form organs.

4. System Level

   • Groups of organs form systems.

5. Organism Level

   • Groups of systems form an organism (the entire body).

Genetics and Inheritance

• DNA and chromosomes are key components.
• Dominant and recessive genes determine traits.

DNA and Chromosomes

• Deoxyribonucleic Acid (DNA): Contained within the nucleus of the cell, separated into strands called chromosomes.
• Most cells have 46 chromosomes arranged into 23 pairs.
• Sex cells (gametes) have 23 chromosomes.
• Gametes from parents each contribute a single set of 23 chromosomes.
• Inheritance explains variation in human characteristics.
• If there's an error on one strand from a parent, the other parent's strand is often fine.

Karyotypes

• A karyotype is a picture of an individual's chromosomes.
• Two chromosomes specify sex: XX for female, XY for male.
• The rest are arranged in pairs, numbered 1 through 22, from largest to smallest.
• This arrangement helps scientists quickly identify chromosomal alterations that may result in a genetic disorder.
• To make a karyotype, scientists take a picture of the chromosome from one cell, cut them out, and arrange them using size, banding pattern, and centromere position as guides.

Genes and Traits

• Gametes contain one set of 23 chromosomes from each parent, resulting in 46 chromosomes in total.
• This combination gives individuals their unique characteristics.
• Dominant Traits: Require only one copy of the gene to be expressed (e.g., brown eyes, detached earlobes, freckles, being right-handed).
• Recessive Traits: Require two copies of the gene to be expressed (e.g., colour blindness, blue eyes, blonde hair).
• Carriers: Have one copy of a recessive gene but do not display the associated trait.

Genes

• A gene is a region on a strand of DNA that regulates one particular aspect of the cell's activities.
• One copy of every gene is given by each parent; this is how traits are inherited.
• The human genetic code includes more than 20,000 genes.
• Genes biologically define who we are.
• Genes are housed in the chromosomes inside the cell nucleus.
• Genes are made of DNA and encode proteins that direct various bodily processes.

Functions of Genes:

1. Building body structures like muscles and bones.
2. Directing body functions such as muscle flexing or hair growth.
3. Supporting bodily functions indirectly like aiding the immune system.
4. Influencing physical traits such as hair colour, eye colour, and skin tone.

• With 20,000 to 30,000 genes in the human body, research continues to explore how genes work individually and together to control both internal operations and our physical appearance.

Genetic Abnormalities and Diseases

• If an individual inherits a faulty gene, or if there is a problem within the chromosomes, a genetic abnormality or disease may result.
• Examples of chromosome problems include:
  • mutations
  • deletions
  • missing or extra chromosomes
• Examples of genetic disorders include:
  • sickle cell anemia
  • Duchenne muscular dystrophy (affects males)
  • cystic fibrosis
  • Down syndrome (trisomy 21): an extra chromosome on 21; the older the mother is during her pregnancy, the more the risk increases of her giving birth to a baby with this type of genetic disorder.