Body Structure & functuon

Genetics and Heredity

  • Definition: Genetics is the study of the hereditary makeup of animals or plants.

  • Role of DNA: DNA controls the structure and function of the entire body; it carries the hereditary information.

  • Unique Genetic Makeup: Each person's DNA and genetic makeup are hereditary, creating a unique genetic fingerprint.

Genetic Engineering

  • Definition: Genetic engineering refers to the intentional use of technology by scientists to change an organism's existing DNA.

  • Caution: This field is relatively new, and its long-term effects are not yet fully understood.

  • Controversy: There are ongoing debates regarding the safety and ethical implications of genetic engineering.

Genetic Fingerprinting

  • Chemical Structure: Everyone's DNA has the same chemical structure; differences are due to the specific order of base pairs.

  • Base Pairs: Each person's DNA contains millions of base pairs.

  • Unique Genetic Makeup: What makes an individual's genetics unique is often referred to as genetic or DNA fingerprinting.

  • Identical Twins: Identical twins are the only instances where two individuals share the same genetic fingerprint.

  • Methods: DNA fingerprinting can be obtained from various biological materials like hair, blood, saliva, etc.

Heredity and Disease

  • Heredity Definition: Heredity is the genetic transmission from parent to child; certain traits are passed down in families.

  • Genes for Traits: Each individual carries two genes for each trait (one from the mother and one from the father).

  • Genetic Disorders: These are medical conditions caused by mutations in a single gene or a set of genes.

    • Definition of Mutation: Mutations are changes in the DNA sequence of a gene or a set of genes, which can occur at any point in life.

    • Congenital Disorders: Genetic disorders present at birth are referred to as congenital disorders or birth defects.

Specific Genetic Disorders

  • Albinism:

    • Nature: A recessive gene mutation causing a hereditary lack of pigment in skin, hair, and eyes.

    • Symptoms: Photophobia and susceptibility to sunburn due to lack of melanin.

  • ADHD (Attention Deficit Hyperactivity Disorder):

    • Definition: A disorder affecting children and adults characterized by difficulty focusing and organizing tasks.

    • Genetic Factors: Genetic predisposition may contribute, with a prevalence 10 times higher in boys than in girls.

    • Treatment: No known cure; treatment often includes medication and counseling. Symptoms may lessen over time.

  • Cleft Palate:

    • Definition: A congenital defect occurring when the palatine bones do not form properly, leading to a passage between the mouth and nasal cavity.

    • Association: Often accompanied by a cleft upper lip.

    • Gender Impact: More common in females than males.

    • Treatment: Surgical repairs are usually performed within the first year and are generally successful.

  • Color Deficiency (Color Blindness):

    • Definition: Difficulty distinguishing between reds and greens, inherited as a sex-linked disorder usually passed from mother to son.

    • Total Color Deficiency: Complete inability to perceive color due to defects in the retinal cones.

  • Cystic Fibrosis:

    • Description: A chronic, progressive disease diagnosed in childhood causing thick, sticky mucus buildup.

    • Implications: Primarily affects lungs (leading to serious respiratory issues) and pancreas (causing malnutrition).

    • Life Expectancy: Average is about 32 years, but new treatments are improving outcomes.

  • Down Syndrome (Trisomy 21):

    • Definition: Caused by an extra chromosome 21.

    • Physical Features: Sloping forehead, short broad hands (single palmar crease), flat nose.

    • Risk Factor: Increased maternal age (over 40) raises risk of having a child with Down syndrome.

    • Diagnosis: Amniocentesis is a common diagnostic tool.

  • Fragile X Syndrome:

    • Also Known As: Martin Bell syndrome, Marker X syndrome, and Fraxa syndrome.

    • Definition: Most common form of inherited mental retardation.

    • Characteristics: Developmental delays, variable intellectual disabilities, emotional and behavioral difficulties; males are generally affected more severely than females.

    • Cause: Mutation in the FMR1 gene on the X chromosome.

  • Hemochromatosis:

    • Definition: An inherited disorder characterized by excessive iron accumulation in the body, common in Caucasians.

    • Symptoms: Often asymptomatic at first; may lead to darkening of the skin due to iron deposits.

    • Gender Differences: Females show organ damage from excessive iron later than males by about 15-20 years.

  • Hemophilia:

    • Definition: A hereditary sex-linked disorder that prolongs blood coagulation times.

    • Symptoms: Increased bleeding time; the genetic mutation is recessive and located on the X chromosome.

    • Transmission: Females carry the gene and typically pass it on to male offspring.

  • Klinefelter Syndrome:

    • Definition: A congenital disorder in males caused by the presence of extra X chromosomes.

    • Symptoms: Small testes, low energy, excessive breast tissue, shyness, learning difficulties.

  • Muscular Dystrophy:

    • Definition: A genetic disease marked by the progressive weakening and atrophy of muscle tissue.

    • Prevalence: More common in males; Duchenne’s muscular dystrophy accounts for 50% of cases.

    • Prognosis: Patients often require a wheelchair by age 12, with a life expectancy of 10-15 years post-symptom onset.

    • Treatment: No cure, but physical therapies may be beneficial.

  • Phenylketonuria (PKU):

    • Definition: Caused by a recessive gene mutation leading to the inability to metabolize phenylalanine.

    • Consequence: Untreated PKU can result in mental retardation due to brain damage; newborn screening is now standard in many states.

  • Sickle Cell Anemia:

    • Nature: A hereditary form of chronic anemia caused by a recessive gene mutation, prevalent in individuals of African or Mediterranean descent.

  • Spina Bifida:

    • Definition: A congenital neural tube defect due to incomplete formation of the vertebrae around the spinal cord.

    • Symptoms: Vary by severity; spinal cord abnormalities are often noticeable at birth.

  • Clubfoot (Pes Planus):

    • Definition: A congenital deformity of the foot that may require treatment with casts or orthopedic shoes.

  • Tay Sachs Disease (TSD):

    • Definition: An inherited disorder affecting the nervous system, predominantly in individuals of Central and Northern European, Jewish or French Canadian ancestry.

    • Symptoms: Appear around six months; symptoms progress to paralysis and death before age five; no known cure exists.

  • Turner Syndrome:

    • Definition: A congenital disorder resulting from dysfunctional ovaries not responding to pituitary hormones.

    • Characteristics: Intelligence deficits, short stature, and amenorrhea may be present.

Case Study and Conclusion

  • Context: Lucy finds that many patients exhibit various genetically related diseases, emphasizing the importance of understanding genetics and heredity in medical contexts.