1. Chapter 15 Heredity and Disease

2. Heredity and Disease Learning Objectives (continued)
Define the functions of DNA, genes, and chromosomes.
Describe several inherited diseases caused by chromosomal abnormalities.
List several chemicals that cause birth defects and the uses of those chemicals.
Explain how a familial pattern of disease differs from a hereditary (genetic) disease.

3. Heredity and Disease Learning Objectives (continued)
Define the symptoms of fetal alcohol syndrome and how the syndrome can be prevented.
Explain the role of genetic counseling in preventing hereditary diseases.
Explain the procedure of amniocentesis.
Define genetic discrimination and its consequences for people.
Discuss how gene therapy and embryonic stem cells may be used to treat and cure disease.

4. Intro Video March of Dimes 5 min
Heredity and Disease
Chromosomal Abnormalities
Congenital Defects
Preventing Hereditary Diseases
Intro Video March of Dimes 5 min

5. Heredity and Disease
One inherits 25,000–30,000 genes from each parent.
Genes are arranged in a linear array along threadlike structures called chromosomes.
Each person carries 23 pairs of chromosomes.
Different genes are expressed in different tissues.

6. Heredity and Disease
DNA—deoxyribonucleic acid—is the chemical substance that carries the genetic information.
Altogether, the 46 human chromosomes have about 200,000 genes that determine each unique characteristic of a human being.

7. DNA—The Molecule of Life

8. Two main categories of birth defects
Structural Birth Defects
Structural birth defects are related to a problem with body parts and structure. These can include:
Cleft lip or cleft palate
Heart defects, such as missing or misshaped valves
Abnormal limbs, such as a clubfoot
Neural tube defects, such as spina bifida, and problems related to the growth and development of the brain and spinal cord

9. Functional, or Developmental Birth Defects
Functional, or developmental, birth defects are related to a problem with how a body part or body system works. These problems often lead to intellectual and developmental disability (IDD) and can include:
Nervous system or brain problems. These include IDDs, behavioral disorders, speech or language difficulties, seizures, and movement trouble. Some examples of birth defects that affect the nervous system include Down syndrome, Prader-Willi syndrome, and Fragile X syndrome.
Sensory problems. Examples include hearing loss and visual problems, such as blindness or deafness.
Metabolic disorders. These involve problems with certain chemical reactions in the body, such as conditions that limit the body’s ability to rid itself of waste materials or harmful chemicals. Two common metabolic disorders are phenylketonuria  and hypothyroidism.
Degenerative disorders. These are conditions that might not be obvious at birth but cause one or more aspects of health to steadily get worse. Examples of degenerative disorders are muscular dystrophy and X-linked adrenoleukodystrophy (ADL), which leads to problems of the nervous system and the adrenal glands and was the subject of the movie "Lorenzo’s Oil."
In some cases, birth defects are caused by a combination of factors. Some recognized patterns of birth defects affect many parts or processes in the body, leading to both structural and functional problems.

10. Heredity and Disease Congenital (Birth) Defect
3% to 4% of American babies are born with one.
Caused by:
Presence of an abnormal chromosome or abnormal number of chromosomes.
A chemical error in one or more genes inherited from parents; the defective gene alters body structure or function.
The effect of toxins, drugs, or other environmental factors on normal fetal development.

11. Chromosomal Abnormalities
Errors can occur when chromosomes are distributed to sperm or egg.
20% of all human conceptions have a chromosomal abnormality of some kind.
Most of these abort spontaneously, resulting in miscarriage.

12. Turner’s
Klinefelter’s
Down’s

13. Chromosomal Abnormalities
Down Syndrome
A chromosome abnormality that involves an extra chromosome 21.
Causes heart defects, altered facial features, and mental retardation.
Life expectancy is about 40–50 years.
1 in every 700 babies.
Risk increases when maternal age is greater than 35, and even more when greater than 40.

14. Chromosomal Abnormalities

15. Chromosomal Abnormalities
Hereditary Diseases
Result when an abnormal gene is passed on to a child from one or both parents.
A protein is produced that is abnormal or completely missing.
If the gene is for an essential muscle protein—muscular dystrophy.
If the gene is for a protein involved in bone formation—dwarfism.

16. Chromosomal Abnormalities
Hereditary Diseases (continued)
Sickle cell disease: defect in hemoglobin proteins, present in all red blood cells; changes the shape of red blood cells, leading to clogs in small blood vessels.
Sometimes these diseases are caused by infections, teratogens, or other environmental factors, as well as by defective genes; they are not always because of familial inheritance.

17. Congenital Abnormalities

18. Congenital Defects
Newborns are examined after birth for observable physical or biological abnormalities, called congenital defects.
Congenital defects are not necessarily inherited, although defective genes from parents may play some role.
Most congenital defects result from complex interactions of genes and environmental factors.

19. Congenital Defects Cleft Lip Spina Bifida
Has occurred in only one of a pair of identical twins; therefore, it can be attributed to both environmental factors and genetics.
Spina Bifida
Affects 1 in 1,000 newborns.

20. Congenital Defects
Vitamin B12 and folic acid supplementation in pregnant women dramatically decrease the risk of spina bifida and other birth defects.
Folic acid—400 micrograms/day, before pregnancy, is recommended.
Folate supplementation before and during pregnancy can reduce the risk of having a child with a birth defect as much as 70%.

21. Cerebral palsy refers to a group of conditions that affect control of movement and posture.  Causes include:
Infections during pregnancy – Certain infections in the mother, including rubella (German measles),cytomegalovirus (a usually mild viral infection) and toxoplasmosis (a usually mild parasitic infection) can cause brain damage and result in cerebral palsy.
Insufficient oxygen reaching the fetus – When the placenta is not functioning properly or it tears away from the wall of the uterus before delivery; the fetus may not receive sufficient oxygen.
Prematurity – Premature babies who weigh less than 3 1/3 pounds are up to 30 times more likely to develop cerebral palsy than full-term babies.
Asphyxia during labor and delivery –asphyxia (lack of oxygen) during a difficult delivery.
Blood Diseases – Rh disease
Other birth defects – Babies with brain malformations, numerous genetic diseases and other physical birth defects are at increased risk of cerebral palsy.
Acquired cerebral palsy– About 10 percent of children with cerebral palsy acquires it after birth due to brain injuries that occur during the first two years of life. The most common causes of such injuries are brain infections, such as meningitis, and head injuries.

22. Congenital Defects Teratogen
Agent that cause a defect in a developing fetus.
Includes many environmental agents, such as prescription and illegal drugs, viral and bacterial infections, and alcohol consumption and smoking during pregnancy.
Thalidomide, diethylstilbestrol, and Accutane are all examples of teratogens.

23. Teratogens

24. Congenital Defects Thalidomide
Developed by a Swiss pharmaceutical company.
In 1956–1961, it was given to pregnant women in Europe and others for morning sickness.
Interferes with normal development of the bones of arms and legs and causes other birth defects.
Not approved in the United States.

25. Congenital Defects DES
In 1950s–1960s, DES was used to help prevent miscarriage.
In the 1970s, daughters of women who took this drug found abnormalities in their reproductive organs when they tried to become pregnant.
Also creates a higher risk of vaginal cancer.

26. Congenital Defects Accutane
A drug for acne causes birth defects (brain, heart, stillbirths).
Many women still used it because they didn’t know they were pregnant, or they became pregnant by accident while taking the drug.

27. Congenital Defects Fetal Alcohol Syndrome
Consumption of alcohol in any amount during pregnancy increases the risk.
Causes certain characteristic abnormal facial features, growth reduction, and neurodevelopmental abnormalities.
Most cases are seen in women who drink large amounts of alcohol during pregnancy

28. Preventing Hereditary Diseases
Prenatal Testing
Amniocentesis
Removal of cells from an amniotic fluid sample, usually done around the 15th week of pregnancy.
Small risk of harming fetus or causing miscarriage.
Cells are tested for biochemical and genetic abnormalities.
Can determine the sex of the fetus.

29. Prenatal Testing

30. Preventing Hereditary Diseases
Prenatal Testing (continued)
Chorionic Villus Sampling
Can be performed as early as 8 weeks into the pregnancy.
Provides information on the health of the fetus.

31. Preventing Hereditary Diseases
Prenatal Testing (continued)
Ultrasound Scanning
Is noninvasive.
Used to visualize the fetus developing in the womb.
Determines placement of placenta.
Gauges fetus’s head size and age.
Can diagnose abnormal brain development and neural tube defects.

32. Preventing Hereditary Diseases

33. Preventing Hereditary Diseases
Genetic Counseling
Used both before and after pregnancy occurs to evaluate risk of conceiving an abnormal fetus.
Very few hereditary diseases can be treated effectively.

34. Preventing Hereditary Diseases
Genetic Testing
Alerts people to their own risk of developing a disease or passing on a defective gene to a child
Useful for preventing passing on genes that cause inherited disorders.

35. Preventing Hereditary Diseases
Genetic Testing (continued)
Genetic tests are available for a broad range of diseases including:
Breast cancer
Colon cancer
Alzheimer’s disease

36. Preventing Hereditary Diseases
Genetic Discrimination
Possibility of discrimination against a person because he or she carries a particular gene that predisposes a person toward a disease.
From employers or insurance companies.

37. Preventing Hereditary Diseases
Treating Hereditary Diseases
Very few can be treated effectively.
PKU (phenylketonuria) can be managed if an affected newborn is diagnosed at birth.
Can cause mental retardation if an affected child eats phenylalanine.

38. Preventing Hereditary Diseases
Gene Therapy
Many human disorders are caused by inheritance of abnormal genes.
Gene therapy is a technique for replacing defective genes with normal ones in certain tissues of a person with a hereditary disease.

39. Preventing Hereditary Diseases
Embryonic Stem Cells
In vitro fertilization (IVF) has led to the creation of laboratory-derived embryos that are used to generate stem cells.
Can be used to find cures for many diseases.
These cells possess the ability to become many different tissues such as lung, heart, liver, brain, etc.

40. Preventing Hereditary Diseases

41. Preventing Hereditary Diseases
Cloning
The production of genetically identical plants and animals.
Animal (including human) cloning is possible by genetic techniques; so far, only animal clones have been made.
The ability to clone humans is an ethical matter, not a technological one.

42. Heredity and Disease
What is your view of the appropriateness of embryonic stem cell research?
What things would make it more or less appropriate?
What is your view of the appropriateness of cloning humans?
Would you use genetic testing to see if a child you had conceived had a defect or abnormality? Why or why not?