Mutations and Genetic Analysis

Question 1

State what is meant by the term ‘trisomy’?

Answer 1

Chromosomal disorder characterised by an additional chromosome

Question 2

Trisomy 21 is known as

Answer 2

Down syndrome

Question 3

Monosomy 45 is known as

Answer 3

Turner syndrome (X)

Question 4

Trisomy 13 is known as

Answer 4

Patau syndrome

Question 5

Trisomy 18 is known as

Answer 5

Edwards syndrome

Question 6

Describe the features of Down syndrome.

Answer 6

• Incidence: 1 in 650 to 700
• Characteristic: Facial Dysmorphologies
• IQ less than 50
  Average life expectancy: 50-60
• Alzheimer’s disease later in life
• Non- Disjunction is maternal origin

Question 7

Describe the features of Patau syndrome.

Answer 7

• Incidence: 1 in 5000
• Multiple dysmorphic features and mental retardation
• About 5% die within the first month, very few survive beyond
• Non - Disjunction is maternal origin
• Unbalanced Robertsonian translocation (10%)

Question 8

Describe the features of Edwards syndrome.

Answer 8

• Incidence: 1 in 3000
• Severe developmental problems: Most patients die within first year, many within first month
• Non - Disjunction is maternal origin

Question 9

47, XXY is known as

Answer 9

Klinefelter syndomre

Question 10

Describe the features of Klinefelter syndrome

Answer 10

• Incidence: 1 in 1000
• Tall stature, long limbs
• Occurs in males but infertile, small testes and about 50% gynaecomastia
• Mild learning difficulties

Question 11

Describe the features of Turner syndrome

Answer 11

• Incidence: 1 in 5000 to 10000
• Occurs in females, short stature and infertile
• Intelligence and lifespan is normal
• Neck webbing and widely spaced nipples

Question 12

Germline mutation

Answer 12

Inheritable mutation of gametes

Question 13

Somatic mutation

Answer 13

Mutations of the other body cells which won’t be passes to future generations

Question 14

Silent mutation

Answer 14

A change in one base still allows the correct amino acid to be used

Question 15

Missense mutation

Answer 15

Correct amino acid is replaced by an incorrect one in the finished protein product

Question 16

Nonsense mutation

Answer 16

The correct amino acid is replaced with a premature stop codon

Question 17

Frameshifts (Deletion/Insertions)

Answer 17

Removal or addition of a base resulting in the sequence after the mutation changing

Question 18

State the practical uses of the polymerase chain reaction (PCR)

Answer 18

• Forensic medicine
• Gene identification
• Detection of mutations
• DNA cloning

Question 19

Contrast the processes of spermatogenesis and oogenesis.

Answer 19

Spermatogenesis - Commence in PUBERTY, 4 sperm cells are formed per meiotic cycle, over a course of around 60 days. More divisions than eggs meaning more chance of mutation.

Oogenesis - Occurs in early EMBRYONIC life, 1 ovum and 3 polar bodies produced per meiotic cycle, process occurs over 10-50 years as the polar bodies mature into ova.