module 7 lec 13 Flashcards
What is epigenetics?
Epigenetics refers to inherited changes in gene expression that do not involve changes in the DNA sequence.
How are methylation patterns inherited?
Methylation patterns are copied during DNA replication, ensuring the same gene expression profile is passed to daughter cells.
What is the role of DNA methyl transferases (DNMTs)?
DNMTs add methyl groups to DNA, often at cytosine residues, influencing gene expression by “closing” chromatin.
What does DNA methylation do to chromatin?
Methylation generally closes chromatin, making it less accessible for transcription, thus silencing gene expression.
Where is DNA methylation most commonly found?
Methylation is common in housekeeping genes (genes needed for basic cell functions), but can also be found in some cell-specific genes.
What is genomic imprinting?
Genomic imprinting is an epigenetic phenomenon where the expression of certain genes is determined by the parent of origin, not just the gene’s sequence.
Is genomic imprinting found in all eukaryotes?
No, genomic imprinting is not observed in all eukaryotes, but it plays a crucial role in mammals and plants.
How does extreme condensation affect gene expression?
Extreme condensation of chromatin completely silences gene transcription by making DNA inaccessible to transcription machinery.
What is the role of DNA methylation in silencing genes?
Methylation at CpG islands promotes chromatin condensation, leading to silencing of genes by preventing access to transcription factors.
Where does DNA condensation typically occur in silencing?
DNA condensation usually occurs in regions where DNA is methylated at CpG islands, contributing to gene silencing.
What is genomic imprinting?
Genomic imprinting involves sex-specific methylation of DNA sequences, known as imprinting control regions, which silences gene expression.
How many genes in humans are affected by imprinting?
Approximately 100 genes in humans show genomic imprinting, with some being maternally imprinted and others paternally imprinted.
How does imprinting change during an individual’s life?
Epigenetic marks (such as imprinting) are erased and regenerated in the germline, but remain stable and affect gene expression throughout the lifetime.
