Early in the book, on the bottom of page 2 and onto page 3,
Dr. Moalem discusses parlance and penetrance. Briefly describe parlance and
penetrance and their connection to our previous unit of genes and the current
unit of gene expression. Explain how penetrance relates to inheritance. Specifically, explain how a gene of low penetrance can be
exhibited in the offspring of someone who expresses that trait using skills learned
from our past target.
Other than hemochromatosis, find evidence of other traits or
genetic diseases with low penetrance and briefly discuss why these genes are of
low penetrance. Also, focusing on Big Ideas 1 and 4, explain how penetrance
leads to diversity based on interactions of genes.
(Morgan Eisenstot – meisens4@students.d125.org)
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ReplyDeleteIn genetics parlance, the degree that a given gene manifest itself in an individual is called penetrance. If a single gene means everyone who carries it will have dimple, that gene has very high or complete penetrance. On the other hand, a gene that requires a host of other circumstances to really manifest, like the gene for hemochromatosis, is considered to have low penetrance (3). For example, we can relate parlance and penetrance to the unit of gene expression, regarding pedigrees-- which is the chart for the inherited diseases or characteristics. Pedigree is formed with information that is gathered on the symptoms of the disease, age of onset, and age at diagnosis. These targeted questions help genetic counselors and researchers identify the typical course of disease in the family, disease severity, possible variable expression, low penetrance, or genetic anticipation.
ReplyDeletePenetrance refers to the proportion of people with a particular genetic change who exhibit signs and symptoms of a genetic disorder. If some people with the mutation do not develop features of the disorder, the condition is said to have low penetrance. Low penetrance and variable expressivity are factors that influence the effects of particular genetic changes. These factors usually affect disorders that have an autosomal dominant pattern of inheritance, although they are occasionally seen in disorders with an autosomal recessive inheritance pattern. (http://ghr.nlm.nih.gov/handbook/inheritance?show=all)
Huntington disease is a progressive brain disorder that causes uncontrolled movements, emotional problems, and loss of thinking ability. (http://ghr.nlm.nih.gov/handbook/inheritance?show=all) One mutated copy of the gene in each cell is sufficient for a person to be affected by an autosomal dominant disorder-- each affected person usually has one affected parent. As with low penetrance, variable expressivity is probably caused by a combination of genetic, environmental, and lifestyle factors, most of which have not been identified.
Big idea 1 (The process of evolution drives the diversity and unity of life.) relates to this topic. Some mutations have a high likelihood of symptoms, whereas others have a low penetrance. The reasons behind the absence of disease in some people, and the development of problems in other people, are not very well understood. Also, big idea 4 (Biological systems interact, and these systems and their interactions possess complex properties.) relates to this topic: Most biological traits are influenced by many genes, environmental conditions and epigenetic expression. According to the genetic researchers, in some cases, other genes act as modifiers on the mutated gene and prevent the unhealthy trait from being expressed.
(Hyung Eun Lee, helee4@students.d125.org)