Genetic and Developmental Disorders

Question 1

What are the classifications of hereditary diseases?

Answer 1

1. Chromosomal
2. Mutational diseases or Mendelian disorders
3. Polygenic disorders

Question 2

What causes chromosomal diseases?

Answer 2

due to an abnormal number of chromosomes or alteration in the structure of one or more chromosomes

Question 3

What causes mutational diseases Mendelian disorders?

Answer 3

due to a defective single gene rather than a chromosomal disorder

Question 4

What are the types of chromosomal diseases?

Answer 4

1. Aberrant number of chromosomes often as a result of a paired homologous chromosomes failing to separate during the 1st or 2nd meiotic division.
   - Monosomy
   - Polysomy: ie Down’s syndrome
2. Abnormal chromosome structure
   - translations- individual with reciprocal translocation is at risk of producing abnormal gamates
   - inversions
   - Delations (tend to have most severe ramifications
   - Duplications (tend to have less severe ramifications

Question 5

What are examples of chromosomal diseases?

Answer 5

1. Klinefelter’s syndrome- males with extra X crhomosome
2. Turner’s syndrome- females with a single X chromosome
3. Down’s Syndrome- Trisomy21 where there are three 21st chromosomes
4. Trisomy 18 or 13: severe mental retardation with shortened life expectancey
5. Cri du Chat Syndrome: Deletion of the short arm of chromosome 5 resulting in severe mental retardation and congenital abnormalities

Question 6

What are examples of mutational diseases or Mendelian disorders?

Answer 6

1. Phenylketonuria (PKU)
2. Cystic Fibrosis (CF)
3. Tay-Sachs
4. Hemophilia
5. Prader-Willi Syndrome
6. Duchene Muscular Dystrophy (DMD)
7. Sickle Cell Anemia
8. Huntington’s Chorea

Question 7

What is Phenylketonuria (PKU)?

Answer 7

• an inability to metabolize an essential amino acid, phenylalanine.
• autosomal recessive disorder resulting in an inborn error in metabolism.

Question 8

What is cystic fibrosis?

Answer 8

• a generalized disease of the exocrine system which affects the respiratory system
• Autosomal recessive disorder of chromosome #7

Question 9

What is Tay-Sachs?

Answer 9

• infantile degeneration of the brain and retina resulting from an abnormal storage of lipids
• children are normal at birth with degeneration starting at about 6 months
• autosomal recessive disorder of chromosome #5

Question 10

What is hemophilia?

Answer 10

• deficiency of factor VIII in the clotting chain

- X linked therefore males express the gene and females carry the gene

Question 11

What is Prader-Willi Syndrome?

Answer 11

• hypotonia in infancy resulting in difficulties in feeding, breathing, and moving
• deletion of chromosome 15

Question 12

What is Duchen muscular dystrophy?

Answer 12

• a progressive muscular dystrophy that begins with proximal weakness and progresses to the entire body
• X linked recessive gene

Question 13

What is sickle cell anemia?

Answer 13

• red blood cells contain sickle shaped hemoglobin which causes increased clotting among other problems
• autosomal dominant

Question 14

What is Huntington’s Chorea?

Answer 14

• mental deterioration and involuntary movements of the arms and legs
• appears in 40’s
• autosomal dominant

Question 15

What causes polygenic disorders?

Answer 15

• involve two or more mutant genes that act together to produce that trait
• greatly influenced by environmental factors as well

Question 16

What are examples of polygenic disorders?

Answer 16

1. heart disease
2. hypertension
3. some cancers

Question 17

What are abnormalities from environmental agents?

Answer 17

teratogenic agents.

• can be broken into classes:
  1. irradiation-exposure to raditation
  2. chemical substances
  3. infections agents

Question 18

When may prenatal death occur?

Answer 18

1 - 2.5 weeks

Question 19

When do major morphological abnormalities occur?

Answer 19

2.5 - 7.5 weeks

Question 20

When do physiological defects, minor morphological defects occur?

Answer 20

7.5 - 9 weeks

Question 21

When does the CNS develop?

Answer 21

2.5 - 6.5 weeks

Question 22

When does the heart develop?

Answer 22

3.5 - 7.5 weeks

Question 23

When do the arms develop?

Answer 23

4.5 - 7.5 weeks

Question 24

When do the eyes develop?

Answer 24

4.5 - 8.75 weeks

Question 25

When do the legs develop?

Answer 25

4.5 to 7.5 weeks

Question 26

When do the teeth develop?

Answer 26

6.5 - 8.75 weeks

Question 27

When does the external genitalita develop?

Answer 27

6.5 - 9 weeks

Question 28

When do the ears develop?

Answer 28

3.5 - 8.75 weeks