BIO 2133 Study Guide - Quiz Guide: Transgenerational Epigenetic Inheritance, X-Inactivation, Gene Dosage
27 Apr 2018
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MODULE 7: EXTRANUCLEAR INHERITANCE, MATERNAL EFFECT,
EPIGENETICS
LEARNING OBJECTIVES
•Distinguish between cytoplasmic modes of inheritance, maternal effects, and epigenetic
inheritance.
Cytoplasmic
Maternal effect
-The Mother’s GENOTYPE determines the offspring's PHENOTYPE.
-When oocyte is made, proteins and mrna are deposited in it. Once the egg is fertilized, proteins
still there and can direct gene expression in early days / weeks. If mom produces a normal
genotype, then even if you are affected it rescue your phenotype
Mitochondrial
Genes code proteins involved in cellular respiration
Genes leading to diseases
Established maternal relatives
Usually Maternal inheritance because of the large size of an oocyte and thus the large concentration
of maternal mitochondria in offspring.
On pedigree, mothers who are afflicted, all this kids are afflicted
Epigenetic inheritance is an unconventional finding. It goes against the idea that inheritance happens
only through the DNA code that passes from parent to offspring. It means that a parent's experiences, in
the form of epigenetic tags, can be passed down to future generations.
Processes by which heritable modifications in gene function occur but are not due to changes in the
base sequence of the DNA of the organism. Examples of epigenetic inheritance are paramutation, X
chromosome inactivation, and parental imprinting.
•Explain how abnormalities in gene dosage can affect phenotype
The "gene dosage effect" hypothesis states that the phenotype is a direct result of the cumulative effect
of the imbalance of the individual genes located on the triplicated chromosome or chromosome region.
This hypothesis was proposed in an attempt to explain the similarities between the phenotypes of
different aneuploid states and the observation that all of the phenotypic traits in DS are also seen in the
general population but at lower frequency, with less severity and usually only present as a single trait.
Gene dosage is the number of copies of a particular gene present in a genome Gene dosage is known
to be related to the amount of gene product the cell is able to express, however, amount of gene product
produced in a cell is more commonly dependent on regulation of gene expression. Nonetheless, changes
in gene dosage (copy number variations) due to gene insertions or deletions can have significant
phenotypic consequences.
•Describe what is epigenetics and mechanisms contributing to it.
Epigenetics is the study of heritable changes in gene expression (active versus inactive genes) that do
not involve changes to the underlying DNA sequence — a change in phenotype without a change in
genotype — which in turn affects how cells read the genes. Epigenetic change is a regular and natural
occurrence but can also be influenced by several factors including age, the environment/lifestyle, and
