Chapter 21 - Epigenetics Flashcards
What is epigenetics?
- Changes in gene expression or
phenotype that are potentially
heritable but that do not alter
the underlying DNA base
sequences. - Typically, very stable from
generation to generation, but
can be induced by
environmental factors.
What are the processes of epigenetic changes?
- Most evidence suggests that
epigenetic effects are brought
about by physical changes in
chromatin structure that affect
the expression of genes. - DNA Methylation
- Histone Modifications
- RNA molecules
What is DNA methylation?
- most well understoof and well studied
- always on cistones
- 5-methylcistone
- supresses transcription
- CPG dinucleotides with mant of these we get CPG islands located in or near promoters
How does DNA methylation work?
methyltransferases recognize semimethylated DNA and add methyl groups to unmethylated cistones
DNA binding proteins sit in major groove one methylated the DNA binding protein cannot sit in the groove
What is histone modification?
- can occur at different amino acids in the tail
- altering chromatin structure
- open: increase gene expression
- close: decrease gene expression
- Polycomb group, large group of proteins that represses transcription by binding and preventing enzymes and proteins necessary to transcription from having access to the DNA
How so RNA molecules impact epigenetic changes?
- Xist
- Paramutations
- cell differentiation
What are the 5 major epigenetic effects?
- Cell differentiation
- Paramutation
- X-inactivation
- Genomic Imprinting
- Monozygotic Twins
What is cell differentiation?
all cells are genetically identical with and away of phenotypes
What is paramutation?
transgenerational epigenetic effect in which one allele of a genotype alters the expression of another allele
* phinipotent
* epi alleles
What is X-inactivation?
- a form of dosage compensation
- controlled by x-inactivation center (Xist, the long noncoding RNA)
- polycomb recessive complex 1
- Tsix and Xist are palendromes
What is genomic imprinting?
- sex of the parent that you get the allele from determines the expression of the allele in the offspring
- typically affect early embryonic development and fetal growth
Mule- Female horse and a Male donkey
Henny - Male horse and a Female donkey
They are not the same phenotype
Genetic Conflict Hypothesis
- suggests that there are differences and conflict motions and paternal allele that affect fetal growth
-paternal alleles are favored evolutionarily (size of offspring)
-maternal alleles limit fetal growth (less strain and stress on mom for labor)
What are monozygitic twins?
Monozygotic twins are twins from the same embryo that split during the development process.
What are some other epigenetic effects?
- Behavioral epigenetics
* Life experiences can have long
lasting effects on behavior and
be passed on to future
generations.
* Maternal behaviors in rats and
children who experience abuse
see an increase in epigenetic
marks. - Effects on metabolism
* Nutrition during prenatal
development can have affects on
health later in life.
* Studies have shown that there
are differences in epigenetic
marks based on the diet of the
parent that altered metabolism
and health in the offspring.
* Environment can also play a
large role in epigenetic marks on
behavior and metabolism.
What is the epigenome?
overall pattern of chromatin modification in the genome
GWAS vs EWAS
* GWAS is constant
* EWAS fare more limited, and always changing
