6. SICKLE CELL DISEASE

Question 1

1. What kind of disease is Sickle Cell Disease?

Answer 1

• it is a type of Autosomal Recessive Disorder

Question 2

2. What is the statistic for the amount of people affected by Sickle Cell Disease?

Answer 2

• 1 out of every 400 African Americans
• 10% of African Americans have the Sickle Cell Trait
  (allele)
• the disease is also very prevalent in sub-tropical
  regions

Question 3

3. What causes Sickle Cell Disease?

Answer 3

• it is caused by the substitution of a single amino acid
• Glutamine is substituted for Valim
• this happens in the Haemoglobin protein
• this happens in red blood cells

Question 4

4. What are 4 symptoms of Sickle Cell Disease?

Answer 4

1. Physical Weakness
2. Pain
3. Organ Damage
4. Paralysis

Question 5

5. How can Sickle Cell Disease be treated?

Answer 5

• blood transfusions every 2 weeks

Question 6

6. What can be said about Heterozygotes of Sickle Cell Disease?

Answer 6

• they are carriers of the Sickle Cell Disease allele
• it is not present in their phenotype
• they are usually healthy
• they can suffer some symptoms

Question 7

7. What is one benefit of being heterozygous for Sickle Cell Disease?

Answer 7

• Heterozygotes are less susceptible to the Malaria
  parasite
• this gives them a survival advantage in the
  Mediterranean and Sub-Tropical regions
• these regions have many Malaria vectors
• this is result of natural selection

Question 8

8. What is Haemoglobin?

Answer 8

• it is a globular protein
• it consists of 4 polypeptides
• 2 alpha chains
• 2 beta chains

Question 9

9. What is Thalassaemia?

Answer 9

• this is an inherited blood disorder
• it is caused when the body doesn’t make enough
  haemoglobin

Question 10

10. What are the symptoms of Thalassaemia?

Answer 10

• unusual bone growth
• enlarged forehead or cheeks
• weak, fragile bones
• osteoporosis
• reduced fertility

Question 11

11. What is Cystic Fibrosis?

Answer 11

• this is the most common lethal genetic disease in the
  United States

Question 12

12. How many people of European Descent suffer from Cystic Fibrosis?

Answer 12

• 1 in every 2 500 people

Question 13

13. What does the Cystic Fibrosis Allele result in?

Answer 13

• it results in defective or absent chloride transport
  channels in the plasma membrane

Question 14

14. What is Cystic Fibrosis characterised by?

Answer 14

• scarring
  (fibrosis)
• cyst formation within the pancreas

Question 15

15. What are the 2 major symptoms of Cystic Fibrosis?

Answer 15

• mucus buildup in some internal organs
• abnormal absorption of nutrients in the small intestine

Question 16

16. What does CTR-1 stand for?

Answer 16

• Copper Transporter Protein 1

Question 17

17. Where is the Copper Transporter Protein 1 located?

Answer 17

• this channel protein is located mostly on intestinal
  epithelial cells
• these cells are responsible for Copper (Cu²⁺0
  absorption

Question 18

18. What leads to CTR-1 deficiency?

Answer 18

• an autosomal recessive disorder due to mutations in
  the CTR-1 protein
• these mutations result in defective copper transport
  proteins

Question 19

19. What is Copper?

Answer 19

• it is an essential trace element

IT IS RESPONSIBLE FOR:
- embryonic development
- myelin production
- mitochondrial and cellular respiration enzyme
functions

Question 20

20. What are the symptoms of CTR-1 deficiency?

Answer 20

• neurological degeneration
• severe developmental delay

Question 21

21. What are Autosomal Dominant Disorders?

Answer 21

• they are inherited disorders
• they are less common than Autosomal Recessive
  Disorders
• the affected individual usually does not survive until
  adulthood
• the affected individual often does not reproduce
• these disorders are caused by dominant alleles

Question 22

22. What is an individual with an Autosomal Dominant Disorder plagued with even if they survive till adulthood?

Answer 22

• the autosomal disorder presents itself in the
  phenotype
• this goes against the natural selection principles

Question 23

23. Why are Autosomal Dominant Disorders rare?

Answer 23

• the affected individual usually dies before mating
• this means that they cannot pass on the gene

Question 24

24. What are exceptions when it comes to Autosomal Dominant Disorders?

Answer 24

• some disorders can express symptoms late in life
• this is known as a late onset of symptoms
• EG: Huntington Disease

Question 25

25. What can be said about dominant alleles that cause a lethal disease?

Answer 25

• they are rare
• they arise by mutation

Question 26

26. What are 2 examples of Autosomal Dominant Disorders?

Answer 26

1. Huntington’s Disease
2. Achondroplasia

Question 27

27. What is Achondroplasia?

Answer 27

• this is a form of dwarfism
• it is caused by a rare dominant allele

Question 28

28. What is Huntington’s Disease?

Answer 28

• this is a neurodegenerative disorder
• it is a degenerative disease of the nervois system

Question 29

29. When does a person with Huntington’s begin to experience symptoms?

Answer 29

• the disease has no phenotypic effects until the
  individual is about 35 to 40 years of age
• the disease is late onset

Question 30

30. What does the timing of the onset of the symptoms of the disease affect?

Answer 30

• it affects the inheritance
• late onset allows mating and offspring production

Question 31

31. What happens to patients with Huntington’s disease when the deterioration of the nervous system starts?

Answer 31

• the effects are irreversible
• the effects are fatal