Lecture 31-32 - Mutations and Cases Flashcards
Mention the 4 categories of mutations.
Germline, Somatic, Spontaneous, Induced mutations
Explain instances in which somatic mutations seems to be inherited between generations. Exp. breast cancer risk is inheritable.
To clarify, somatic mutations are not inheritable. However, risk factors (germline mutation) is inheritable and it may TRIGGER somatic mutations, hence giving the appearance of an inheritable somatic mutation.
Spontaneous mutations occur during the _______ stage of cell division.
DNA synthesis.
What are mutagens?
Mutagens are physical or chemical agents that increase the rate genetic material changes.
Compare chromosomal and small mutations.
Chromosomal mutations can involve many genes.
Smaller mutations can occur in coding regions (affecting gene product) or non-coding regions (affect gene expression).
Mention the four types of chromosomal mutations.
Deletion, duplication, inversion, translocation
How are inversion mutations and deletion mutations differ?
Inversion mutations do not change the amount of genetic material, while deletion change the amount of genetic material.
Mention three types of single base pair deletion mutations.
Silent, Missense, Nonsense mutations
Explain aspects of the genetic code that allows some single base mutations to be unexpressed.
The degeneracy of the code describes how some codons encode for the same amino acids hence some mutation change one codon to another codon encoding the same amino acid. The same mechanism happen with the wobble nature of the code, where the last base of the codon does not matter in determining the expression of the amino acid.
What happens in a nonsense mutation? Is it always detrimental in the aspect on its effect on the normal functioning of the proteins?
Nonsense mutations lead to the premature termination of translation (due to the expression of the stop codon). The effects of the mutation depends on the location in respect to the gene, if its near to the end, the effects might be minute compared to it happening in the beginning if translation.
Why is the deletion/insertion of 1 base might be more destructive compared to the same mutation but with 3 bases?
If the deletion/insertion of bases involves a number not divisible by three, it will lead to a frameshift mutation, where the translation machinery will “read” and translate the code incorrectly for the rest of the template. I fit were 3 (6, 9, etc) no. of bases, the mutation would only involve the addition/deletion of amino acid rather than mistranslating the entire the code.
What are the most common mutation associated with cystic fibrosis?
In-frame deletion of phenylalanine
How does the mutation correlated with cystic fibrosis affect protein functioning?
A mutation cause a defect in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The mutation cause a build up of Cl- ion, which in turn leads to the accumulation of sticky mucus in the ducts of the respiratory ducts.
What are the two key components of haemoglobin?
alpha and beta globin, iron core
How are sickle cell anaemia and thalassemia different?
Sickle cell anaemia is caused by a single base pair mutation in the beta subunit, causing a missense mutation (glutamic acid –> valine). This cause a change in charge in the site, leading to the aggregation of sickle Hb.
Thalassemia is caused by a mutation in either alpha or beta subunits, leading to the decreased in production or stability of either globin respectively.
