Unit 4 (Week 14 Epigenetics, Linkage, and Extranuclear Inheritance) Flashcards
Mendelian inheritance patterns follow three general rules which are? (3)
- Except in the case of rare mutations, genes are passed unaltered from cell to cell, and from generation to generation.
- The genes obey Mendel’s law of segregation.
- For crosses involving two or more genes, the genes obey Mendel’s law of independent assortment.
Select all that apply
What are the three general rules for genes that follow a Mendelian pattern of inheritance?
Multiple select question.
The genes interact in an additive way to produce a phenotype.
For crosses involving two or more genes, the genes obey Mendel’s law of independent assortment.
The genes obey Mendel’s law of segregation.
Genes are generally passed unaltered from cell to cell, and from generation to generation.
For crosses involving two or more genes, the genes obey Mendel’s law of independent assortment.
The genes obey Mendel’s law of segregation.
Genes are generally passed unaltered from cell to cell, and from generation to generation.
Who coined the term epigenetics in 1941?
Conrad Waddington. Prefix, epi, means over, which suggests that some types of changes in gene expression are at a level that goes beyond changes in DNA sequences.
How do geneticists distinguish an epigenetic effect from other types of gene regulation?
An epigenetic effect begins with an initial event that causes a change in gene expression.
For example, DNA methylation may inhibit transcription. However, for this to be an epigenetic effect, the change must be passed from cell to cell and must not involve a change in the sequence of DNA.
What is the key feature of an epigenetic effect?
The long-term maintenance of a change in genetic expression.
As an example, let’s consider muscle cells in humans. Some genes in the human genome should be expressed in muscle cells, such as the genes that encode the proteins called actin and myosin, which are required for muscle contraction.
In embryonic muscle cells, these genes are subjected to epigenetic changes that promote their expression through adulthood. Alternatively, in other cell types, these same genes are inhibited by epigenetic changes such as DNA methylation. As the embryo grows and eventually becomes an adult, these epigenetic changes are passed from cell to cell so that adult muscle cells express actin and myosin genes at very high levels, whereas many other cell types do not.
T/F Some epigenetic changes, such as those involving the expression or inhibition of actin and myosin genes, are relatively permanent during the life of an individual.
True.
However, other epigenetic changes may be reversible during the life of an individual or may be reversible from one generation to the next.
What is the process in which certain species of plants require an exposure to cold temperatures in order to flower?
Vernalization
After vernalization, plants do not necessarily initiate flowering, but they acquire the ability to do so. Most commonly, plants are vernalized by exposure to cold winter temperatures and then flower the following spring or summer.
Vernalization involves epigenetic changes to genes that play a role in flowering. These epigenetic changes are induced by cold winter temperatures, and they are maintained during the flowering season. However, the epigenetic changes are reversed after the flowering season is over.
What is the study of mechanisms that lead to changes in gene expression that can be passed from cell to cell and are reversible, but do not involve a change in sequence of DNA?
Epigenetics.
This type of change may also be called EPIMUTATION.
This is a heritable change in gene expression that does not alter the sequence of DNA.
What is an epigenetic change that is passes from parent to offspring? An example is genomic imprinting.
Epigenetic inheritance
What is a case of epigenetic changes that are not inherited from parents?
For example, a person may be exposed to an environmental agent in cigarette smoke that causes an epigenetic change in a lung cell that is subsequently transmitted from cell to cell and promotes lung cancer. Such a change would not be transmitted to offspring.
What are the MOST common types of molecular changes that underlie epigenetic effects on gene expression?
- DNA methylation
- Chromatin remodeling
- Covalent histone modification
- Localization of histone variants
These types of changes are also involved in transient (nonepigenetic) gene regulation that is not transmitted from cell to cell.
The term which describes changes in gene expression that are not related to variations of the DNA sequence, yet are transmissible and are reversible, is __________
epigenetics or epigenetic
True or false: An epigenetic effect causes a change in gene expression without altering the sequence of DNA.
True false question.
True
False
True
Which of the following statements best describes epigenetic changes during the life of an individual?
Multiple choice question.
Some epigenetic changes are permanent while others are reversible.
All epigenetic changes are permanent and irreversible.
All epigenetic changes are transient and reversible.
Some epigenetic changes are permanent while others are reversible.
The molecular mechanisms of epigenetics are varied. The most common types are: DNA ________, chromatin ________, covalent ________ modification, and localization of histone variants.
Methylation, remodeling, and histone
Mendelian inheritance is characterized by three general rules: 1. Except in the case of rare _______, genes are passed unaltered from generation to generation; 2. Each gene obeys Mendel’s law of __________; and 3. During crosses, two or more genes obey Mendel’s law of independent __________-.
Mutations, segregation, assortment
What type of inheritance describes genomic imprinting?
Multiple choice question.
Mendelian
Extranuclear
Epigenetic
Mitochondrial
Epistatic
Epigenetic
Select all that apply
Which of the following statements are true regarding epigenetics?
Multiple select question.
Epigenetic changes may be transmitted to offspring.
Epigenetic changes are transmissible from cell to cell.
Variations of gene expression that result from DNA mutations
Variations are reversible from one generation to the next.
Variations of gene expression that are unrelated to DNA sequence variants
Epigenetic changes may be transmitted to offspring.
Epigenetic changes are transmissible from cell to cell.
Variations are reversible from one generation to the next.
Variations of gene expression that are unrelated to DNA sequence variants
Which of the following characterize an epigenetic effect?
Multiple select question.
The change must be passed from cell to cell
Leads to changes in the DNA sequence
Has no effect on gene expression
Causes a change in gene expression
The change must be passed from cell to cell
Causes a change in gene expression
[Information on Chromatin Modifications]
DNA methylation
Methyl groups may be attached to cytosine bases in DNA. When this occurs near promoters, transcription is usually repressed.
Chromatin remodeling
Nucleosomes may be moved to new locations or evicted. When such changes occur in the vicinity of promoters, the level of transcription may be altered. Also, larger-scale changes in chromatin structure may occur, such as those that happen during X-chromosome inactivation in female mammals, discussed later in this chapter.
Covalent histone modification
Specific amino acid side chains in the amino terminal tails of histones can be covalently modified. For example, they can be acetylated or phosphorylated. Such modifications may repress or activate transcription.
Localization of histone variants
Histone variants may become localized to specific locations, such as near the promoters of genes, and affect transcription.
None
[18.2 Epigenetics I: Genomic Imprinting]
What does the term imprinting implie?
A type of marking process that has memory.
For example, newly hatched birds identify marks on their parents, which allows them to distinguish their parents from other individuals.
What is the phenomenon in which a segment of DNA is imprinted, or marked, during egg or sperm formation in a way that affects gene expression throughout the life of the individual who inherits that DNA?
Genomic imprinting
However, depending on the gene, it may be marked by females during egg formation or by males during sperm formation, but not both. This marking process, which involves epigenetic modifications, affects whether or not the gene is expressed in the offspring.
What is dependent on how a particular gene is marked by one of the parents?
The offspring expresses either the maternal or the parental allele, but not both.
Does imprinting follow the Mendelian pattern of inheritance?
No, imprinted genes do not follow a Mendelian pattern of inheritance because imprinting causes the offspring to distinguish between maternal and paternal alleles.