21. Epigenetics I Flashcards
(19 cards)
What are the two crucial aspects of controlled gene expression?
Timing and location
Timing refers to when genes are expressed, and location refers to which tissues or cells express specific genes.
What does the term ‘epigenetics’ literally mean?
‘On top of genetics’
It refers to processes that induce changes in gene activity without altering the DNA sequence.
What is the effect of low methylation on gene expression?
Gene activation
Low methylation allows transcription factors to bind, promoting gene expression.
What is the most common form of DNA methylation?
Addition of a methyl group to cytosine, resulting in 5-methylcytosine
This process primarily occurs at CpG sites.
What role do DNA methyltransferases (DNMTs) play in DNA methylation?
They add methyl groups to cytosine
DNMT1 maintains methylation during cell division, while DNMT3A/3B establishes new methylation patterns.
What are the two main types of chromatin?
Euchromatin and heterochromatin
Euchromatin is loosely packed with high transcriptional activity, while heterochromatin is densely packed with low transcriptional activity.
Fill in the blank: Histone acetylation is associated with _______.
Gene activation
Acetylation neutralizes the positive charge of histone tails, leading to a more open chromatin structure.
What type of histone modification is H3K4me3 associated with?
Gene activation
H3K4me3 stands for trimethylation of lysine 4 on histone 3.
What are the three types of actors in histone modification processes?
Writers, readers, and erasers
Writers add modifications, readers interpret them, and erasers remove them.
What is the function of microRNAs (miRNAs)?
Bind to mRNAs, causing degradation or translation inhibition
Each miRNA can target multiple mRNAs, influencing gene expression.
What is the significance of the Maternal-to-Zygotic Transition (MZT)?
Transition from maternal mRNAs to zygotic gene expression
This process involves degradation of maternal mRNAs and activation of zygotic genes.
What are the two cell types formed during blastocyst development?
Trophectoderm (TE) and inner cell mass (ICM)
TE forms extraembryonic tissues, while ICM is pluripotent and forms all three germ layers.
What is the role of OCT4 in stem cell maintenance?
Regulates pluripotency and self-renewal
It works with NANOG and SOX2 to maintain stem cell characteristics.
True or False: Epigenetic mechanisms change the DNA sequence.
False
Epigenetics regulates gene expression without altering the underlying DNA sequence.
What are the three major epigenetic mechanisms?
DNA methylation, histone modifications, and non-coding RNAs
These mechanisms work together to control gene expression and cell fate.
What is the primary consequence of high methylation on gene expression?
Gene repression
High methylation prevents transcription factors from binding, inhibiting gene expression.
Which enzymes are responsible for removing methylation from DNA?
TET enzymes
They oxidize 5-methylcytosine to remove methyl groups.
Fill in the blank: The basic unit of chromatin is called a _______.
Nucleosome
A nucleosome consists of DNA wrapped around histone proteins.
What is the primary function of long non-coding RNAs?
Regulate gene expression
They play critical roles in various cellular processes despite not coding for proteins.
