Exam 7: Genetic Variation Producing Diseasecausing Abnormalities in Dna and Chromosomes

Correct Answer:

Verified

b) 100% of all possible changes to the second base cause an altered interpretation for the codon.
c) About 30% of all possible changes to the third base cause an altered interpretation for the codon.

Correct Answer:

Verified

If the two breaks occur on the same chromosome arm, there are two possibilities. First an interstitial deletion can result, after the central piece is excised and the two ends are fused at the breakpoints (the excised central fragment cannot be propagated because it lacks a centromere). Alternatively, a paracentric inversion results (the central piece, lacking a centromere, rotates and then is fused to the end pieces).
If the two breaks occur on different chromosome arms, deletion is not normally viable: the central fragment cannot be excised and lost as it contains the centromere. Instead, there are two viable alternatives. First, a pericentric inversion results (the central piece, containing a centromere, rotates and then is fused to the end pieces). More rarely, a ring chromosome can occur where the two ends of the central fragment fuse to form a circular chromosome.

Correct Answer:

Verified

Amyloid protein is the term used to describe a broad family of proteins that have a high content of $\beta$ -sheets that make them prone to aggregation. Prions are a well-known subclass of amyloid proteins but in addition there are many other examples. Amyloid diseases are disorders in which amyloid proteins are implicated. The aggregation of amyloid proteins can occur outside of cells (such as in the case of prion proteins and $\beta$ -amyloid), within nuclei (huntingtin), or within the cytoplasm (SOD1; Tau; and synuclein).
Some common amyloid diseases are not associated with neurodegeneration, such as type 2 diabetes (aggregates of serum amyloid A protein are found in the pancreatic islets of Langerhans). However, neurodegeneration is the most striking clinical characteristic of many amyloid diseases.
Alzheimer disease, Parkison disease, amyotrophic lateral sclerosis, and frontotemporal disease, resemble prion protein diseases in many ways and are sometimes classified as prionoid diseases. In these diseases direct involvement of the aggregated proteins in disease is supported from familial forms of these disorders in which mutations in the relevant gene promote the formation of amyloid protein.
There is no evidence from animal studies that the aggregated proteins in prionoid disorders are infectious like prion proteins. But there is quite strong evidence that the pathogenesis resembles prion protein disease in two respects. First, like prion proteins, misfolded amyloid proteins in these disorders can induce the formation of the amyloid state in the normal proteins so that they aggregate. Secondly, for several of the disorders there is strong evidence for cell-to-cell spreading of the disorder.