Chromosome Abnormalities, Mutations & Analysis Flashcards
Types of Chromosome Abnormalities
Numerical
Structural
Mutational
Numerical
Trisomy
Monosomy
Trisomy
Patau
Edwards
Down
Klinfelter
Patau
47 XX +13
Edwards
47 XY +18
Down
47 XX +21
Klinefelter
47 XXY
Monosomy
Turner
Turner
45 X
Origins of chromosome abnormalities
Non-disjunction at meiosis I
Non-disjunction at meiosis II
Non-disjunction at meiosis I
2 gametes with disomy
Non-disjunction at meiosis II
2 normal gametes and one with disomy
Why are origins of non-disjunction maternal?
Females developing ova as developing babies and when they are born they have all their eggs
Arrested at meiosis I
Longer period of arrest = abnormalities
Characteristic of Trisomy 21 (5)
Downs Distinct facial features Low IQ Increases in advanced maternal age Unbalanced Robertsonian translocation
Characteristic of Trisomy 13 (5)
Patau syndrome Mental retardation Dysmorphic features Maternal origin- non-disjunction Unbalanced Robertsonian
Characteristic of Trisomy 18 (4)
Edwards syndrome
Severe developmental problems
Most patients die within first year
Non-disjunction (maternal)
Characteristic of Aneuploidy (Monosomy) Syndrome
Turner syndrome
appear females- short stature and infertile
Characteristic of 47 XXY
Klinefelter syndrome Tall stature, long limbs Male but infertile, small testes Gynaecomastia Mild learning difficulties
Structural
Balanced or unbalanced rearrangements Translocations Deletions Insertions Inversions
Outcomes of Balanced Translocation
Normal
Balanced
Partial trisomy + partial monosomy
Reciprocal Translocation
Involving breaks in 2 chromosomes with formation of two new derivative chromosomes
Robertsonian Translocation
Fusion of two acrocentric chromosomes
Loss of short arms
Outcomes of Robertsonian Translocation
Trisomony (chromosome)
Monosomy (chromsome)
Deletions
Interstitial
Terminal
Inversions
Paracentric
Pericentric
Pericentric
Piece involves Centromere
Genetic
Germ line or Somatic
Non-coding or Coding
Coding
Silent- codon change, aa stays the same
Missense- amm changes
Nonsense- stop codon
Franeshift
Point Mutations
Transition
Transversion
Transitions
Purine to Purine
Pyrimidine to Pyrimidine
Transversions
Purine to Pyrimidine
Pyrimidine to Purine
Cys64Arg
• At position 64, mutation from Cys to Arg
M252X
• Mutation at position 252 to stop codon
1294del40
Deletion of 40 nucleotides at position 1294
1298A>G
Position 1298 mutation of A >G
662-42C>T
Introns use position of exons Position 662 -42 has mutation of C > T
IVS2+12insG
Position IVS2 + 12 nucleotides has insertion of G
Detecting Mutations
PCR
Gel electrophiresis
Restriction fragment length polymorphism analysis (RFLP)
Amplification refractory mutation system (ARMS)
DNA sequence
PCR
Oligonucleotide primers
Denature
Anneal primers and nucleotide
Extend with DNA polymerase
Gel Electrophoresis
Separate DNA fragments by size
Across electric field
DNA is negatively charged
RFLP
Enzymes from bacterial cells
Recognise specific DNA sequences (4-8bp)
Cut DNA
Requires gel electrophoresis or southern blot
ARMS
Normal primer matches= amplification of wild type
Mutant primer = no amplification
Mutant primer attaches= amplification of mutant alleles
Normal primer= no amplification
Electrophoresis required
DNA Sequence
Uses dideoxynucleotides
ddATP, ddCTP, ddGTP, ddTTP
Gold standard for mutation detection
Uses gel electrophoresis