Mutations and Detection Flashcards
What are the 3 types of chromosomal abnormalities?
Numerical, structural, mutational
What are the 2 kinds of structural translocations?
Reciprocal or Robertsonian
What occurs in a reciprocal abnormality?
Equal parts of 2 chromosomes are swapped over, so no DNA is lost or gained.
What is the outcome of a reciprocal abnormality?
If gamete receives both normal chromatids, they will have a normal zygote. If gamete received both translocated chromatids, they will have a balanced translocation. If gamete receives one normal and one translocated chromatid, they will have unbalanced translocation
What does unbalanced translocation result in?
In reciprocal, a partial trisomy/monosomy. In robertsonian, a trisomy or monosomy
What are the 4 types of structural abnormality?
Translocation, Insertion, Deletion, Inversion
Which kind of mutation can lead to trisomy 21 and what is the disease associated with this?
Robertsonian translocation can lead to trisomy 21 which is down syndrome
Germline vs Somatic?
Germline involves germ cells - egg and sperm. Somatic involves all other chromosomes
What is a polymorphic genetic mutation?
No phenotypic effect associated. Very common and found in more than 1% of out genomes
What is a non-coding mutation?
One which occurs in a region of DNA that doesn’t code for proteins. Could still have an effect if its in a promoter region
What are the 4 coding mutations?
Silent, missense, nonsense and frameshift
What is a silent mutation?
One that doesn’t affect the outcome of protein as the 3-base codon codes for the same amino acid as before the mutation
What is a missense mutation?
A change in a codon which leads to another amino acid being transcribed. Could have a serious effect
What is a non-sense mutation?
Amino acid changed to a ‘stop’ codon so protein is shorter. Could have serious effect
What is a frameshift mutation?
Codon added or deleted so all other codes shift and many amino acids are changed. Has large detrimental effect usually as it produces totally different protein product
What are the 5 listed methods of detecting mutations?
PCR
Gel electrophoresis
DNA analysis
Restriction fragment length polymerisation (RFLP)
Amplification refraction mutation system (ARMS)
What occurs in a numerical mutation?
Number of chromosomes is altered, usually +/- 1
What is an example of two numerical mutations?
(-45, X) leads to only 1 X chromosome - Turner syndrome. (-47, XXY) leads to extra X chromosome in men - infertile, tall male with small testes
What increases the chance of a child having Down syndrome?
Mothers age. Older woman has has her ova sitting in meiosis 1 for a long time, so more likely mutation has occured
Which trisomy is more commonly seen and why?
Smaller chromosomes, e.g. 18, 21. These typically are Afrocentric. This is because trisomy in larger chromosomes (smaller numbers) do not survive typically.
What is the process of a mutation as a result of non-dysjunction?
When homologous chromosomes fail to separate at meiosis resulting in a germ cell containing 24 chromosomes rather than 23
What is sickle cell known to provide resistance to?
Malaria
