Clear and orderly summary of Chapter 16 of the book "Genetics: Analysis and Principles, 6th Edition by Robert Brooker". Together with all my other summaries of Genetics I got an 8,5 for this course.
Genetics summary Chapter 16 – Gene regulation in Eukaryotes II:
epigenetics
Epigenetics; field of genetics that explore changes in gene expression that may be
permanent over the course of an individual’s life but not permanent over the course
of multiple generations
16.1 Overview of epigenetics
‘Epi’ means over, suggest that types of changes in gene expression are at a level
that goes beyond changes in DNA sequence.
Epigenetic begins with a change in gene expression, the change must be passed
from cell to cell. It does NOT involve change in sequence of DNA.
Some changes permanent other reversible.
Epimutation; heritable (erfelijke) change in gene expression that does NOT alter
sequence of DNA
Epigenetic inheritance (erfenis)/transgenerational epigenetic inheritance; epigenetic
change passed from parent to offspring.
Types of molecular changes underlie epigenetic gene regulation
Molecular changes that underlie epigenetic control;
- DNA methylation
- Chromatin remodeling
- Covalent histone modification
- Histone variants
- Feedback loops
Epigenetic changes target (doelwit) to specific genes by transcription factors or non-
coding RNAs
Targeting a gene for epigenetic modification by
- Transcription factors; transcription factor bind to
specific gene. Transcription factors recruits
histone-modifying enzymes and DNA
methyltransferase. Changes in chromatin
structure and/or DNA methylation Changes alter
gene expression
- Non-coding RNA (ncRNAs) (RNAs that do not
encode polypeptides); see transcription factors.
Only not transcription factor bond to specific gene
but noncoding RNA
Epigenetic changes maintained by cis- or trans-epigenetic
mechanisms
Cis-epigenetic mechanism; effect only one copy of a gene that has
two copies.
caused by DNA methylation or changes in chromatin structure
examples are genomic imprinting and X-chromosome inactivation
, Trans-epigenetic mechanism; effect both copies of a gene that has two copies.
caused by diffusible transcription factors that constitute feedback loop
example is feedback loop and paramutation
Epigenetic occur as a programmed developmental
change or cause by environmental agents.
Programmed changes during development
- Genomic imprinting
- X-chromosome inactivation
- Cell differentiation
Environmental agents
- Temperature
- Diet
- Toxins
16.2 Epigenetics and
development
Development; involves a
series of genetically
programmed stages in which
an egg become an embryo and an adult.
Changes during the development
- Genomic imprinting
- X-chromosome inactivation
- Cell differentiation; formation of specific cell types and tissues
Genomic imprinting
Imprinting of Ifg2 gene occurs during gametogenesis and involves DNA methylation
that happens during spermatogenesis but NOT during oogenesis.
Ifg2 is located next to gene H19, play a role in forms of cancer.
Imprinting control region (ICR); methylation may occur here. Located between H19
and Igf2 genes.
Differentially methylated region (DMR); site that is methylated during
spermatogenesis or oogenesis but NOT both
(differentially)
During oogenesis; methylation does not occur.
CTC-binding factor (CTCF) bind to DNA
sequence ICR and DMR. They form a loop.
The loop prevents the enhancer from
stimulation Igf2. Igf2 OFF
During spermatogenesis; methylation does occur. ICR and DMR are methylated.
Enhancer stimulate the Igf2 gene. Ifg2 ON
Novo methylation sperm cells. Maintenance methylation somatic cells of
offspring
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