Mutations and Genetic Analysis Flashcards
State what is meant by the term ‘trisomy’?
Chromosomal disorder characterised by an additional chromosome
Trisomy 21 is known as
Down syndrome
Monosomy 45 is known as
Turner syndrome (X)
Trisomy 13 is known as
Patau syndrome
Trisomy 18 is known as
Edwards syndrome
Describe the features of Down syndrome.
- 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
Describe the features of Patau syndrome.
- 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%)
Describe the features of Edwards syndrome.
- Incidence: 1 in 3000
- Severe developmental problems: Most patients die within first year, many within first month
- Non - Disjunction is maternal origin
47, XXY is known as
Klinefelter syndomre
Describe the features of Klinefelter syndrome
- Incidence: 1 in 1000
- Tall stature, long limbs
- Occurs in males but infertile, small testes and about 50% gynaecomastia
- Mild learning difficulties
Describe the features of Turner syndrome
- Incidence: 1 in 5000 to 10000
- Occurs in females, short stature and infertile
- Intelligence and lifespan is normal
- Neck webbing and widely spaced nipples
Germline mutation
Inheritable mutation of gametes
Somatic mutation
Mutations of the other body cells which won’t be passes to future generations
Silent mutation
A change in one base still allows the correct amino acid to be used
Missense mutation
Correct amino acid is replaced by an incorrect one in the finished protein product
Nonsense mutation
The correct amino acid is replaced with a premature stop codon
Frameshifts (Deletion/Insertions)
Removal or addition of a base resulting in the sequence after the mutation changing
State the practical uses of the polymerase chain reaction (PCR)
- Forensic medicine
- Gene identification
- Detection of mutations
- DNA cloning
Contrast the processes of spermatogenesis and oogenesis.
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.
