Chromosomal Biology 2 Flashcards
What is non-disjunction?
Failure of homologous chromosomes or sister chromatids to separate properly during cell division
Name autosomal aneuploidy syndromes.
Down Syndrome
Patau Syndrome
Edwards Syndrome
In Down syndrome where is the extra chromosome?
21
In Patau syndrome where is the extra chromosome?
13
In Edwards syndrome where is the extra chromosome?
18
Name sex chromosomes aneuploidy syndromes.
Turners syndrome (45, X) Klinefelter syndrome (47,XXY)
What are the classes of chromosomal structural abnormalities?
balanced or unbalanced arrangements translocations deletions insertions inversions
What are the two kinds of translocations?
Reciprocal and Robertsonian
What is reciprocal translocation?
Involves breaks in two chromosomes with formation of two new derivative chromosomes
What is Robersonian translocation?
Fusion of two afrocentric chromosomes
What can unbalanced translocation lead to?
a partial trisomy and a partial monosomy
What are the different types of coding mutations?
Silent/synonymous (polymorphism)
missense
nonsense
frameshift (insertion/deletion)
What are the two kinds of point mutations?
Transitions - purine to purine or pyrimidine to pyrimidine
Transversions - purine to pyrimidine, pyrimidine to purine
What techniques can be used to detect mutations?
Polymerase chain reaction (PCR)
gel electrophoresis
restriction fragment length polymorphism (RFLP) analysis
amplification refractory mutation system (ARMS)
DNA sequencing
What is needed for PCR?
sequence information oligonucleotide primers DNA nucleotides DNA polymerase
What are the 4 steps of PCR?
denature, anneal, extend, repeat
What does electrophoresis do and how?
separates DNA fragments by size
by applying electric field, DNA is negative charged so it is separated through agarose gel matrix allow visualisation of DNA fragments
What are the advantages of electrophoresis?
speed
ease of use
sensitive
robust
What are the applications of PCR?
DNA cloning DNA sequencing in vitro mutagenesis gene identification gene expression studies forensic medicine typing genetic markers detection of mutations
How does ARMS work?
By using normal and mutant primers and detecting amplification using both, will show if mutant or wild type DNA
What are the advantages of ARMS?
cheap
labelling not required
What are the disadvantages of ARMS?
electrophoresis required
primer design critical
need sequence information
limited amplification size
What are restriction endonuclease?
Enzymes from bacterial cells which degrade DNA of invading viruses (by recognising specific DNA sequences (always cut at same site on DNA))
How can these be used in detecting mutations?
If the DNA is mutant endonuclease won’t recognise it and so won’t cut it so only one long fragment will show up on electrophoresis, if normal shows up as two fragments, and if heterozygous shows up as one long and two shorter fragments.
What are the advantages and disadvantages of using restriction endonuclease?
Simple
cheap
non-radioactive
requires gel electrophoresis
not always feasible
What does the Sanger Sequencing method use?
Dideoxynucleotides
What are the advantages and disadvantages of Sanger sequencing?
Gold standard for mutation detection
automation and high throughput
expensive equipment
poor quality sequence read
