Lecture 1 - chromosome abnormalities in human disease

Question 1

What are the 4 types of human genetic disease?

Answer 1

• Single gene disorders (cystic fibrosis)
• Genetic components of complex disease (diabetes)
• Chromosomal abnormalities
• Mitochondrial diseases

Question 2

What is aneuploidy?

Answer 2

Extra or lost chromosomes

Question 3

What are 3 examples of aneuploidy?

Answer 3

• Down syndrome (trisomy 21)
• Klinefelter syndrome (XYY)
• Turner syndrome (X0)

Question 4

What are examples of changes in chromosome structure (right number of chromosomes but severe change in chromosome)?

Answer 4

• Deletions
• Duplications
• Inversions
• Reciprocal translocations
• Robertsonian translocation - can lead to Down’s syndrome

Question 5

What are P & Q arms on chromosomes?

Answer 5

• P (short arm)
• Q (long arm)
  on chromosomes

Centromere = end of P & start of Q

Question 6

Describe the difference between polyploidy & aneuploidy

Answer 6

Polyploidy - number of copies of all sets of chromosome (e.g. triploid = 3 sets of 23 pairs in humans)

Aneuploidy - chromosome number is not normal but not the whole set

Question 7

What are characteristics of Down syndrome (trisomy 21)?

Answer 7

• Growth failure
• Mental retardation
• abnormal ears
• flat back of head
• short hands
• absence of rib
• intestinal blockage
• enlarged colon
• big toes widely spaced
• diminished muscle tone

Question 8

What are 2 other examples of human autosomal trisomics?

Answer 8

• Patau syndrome (trisomy 13)
• Edward’s syndrome

Question 9

What is Patau syndrome?

Answer 9

• Severe physical and mental abnormalities
• Harelip
• Small head
• Rocker-bottom feet
• Life expectancy of 130 days (average)

Question 10

What is Edwards syndrome (trisomy 18)?

Answer 10

• severe physical and mental abnormalities
• ‘faunlike’ ears
• small jaw
• narrow pelvis
• life expectancy - several weeks (average)

Question 11

What are 2 examples of sex chromosome disorders?

Answer 11

• Klinefelter syndrome (XXY)
• Turner syndrome (X0)

Question 12

What is Klinefelter syndrome (XXY)?

Answer 12

• Tall stature
• Slightly feminized physique
• Tendency to lose chest hair
• Female pubic hair
• Small testes
• Osteoporosis (weak bones)
• breast development

Question 13

What is Turner syndrome (X0)?

Answer 13

• short stature
• low hairline
• widely spaced nipples
• small fingernails
• brown spots
• no menstruation
• rudimentary ovaries
• elbow deformity
• poor breast development

Question 14

What is the only viable monosomy?

Answer 14

Turner’s syndrome