D2 Flashcards
What is gene regulation?
Control of the timing, location and amount of genes expressed in an organism. Can lead to cell specialisation, or adaptation to environment
What is a phenotype?
Physical traits resulting from the specific proteins an individual has due to their expressed genes
What is mRNA degradation?
The use of enzymes to break mRNA into nucleotides for recycling. This is done by removing the poly A tail and the GTP cap before breaking the bonds between nucleotides
What are exonucleases?
Enzymes that break down nucleic acids by removing individual nucleotides. Crucial for mRNA degradation
What is epigenesis?
The process of changing the phenotype of a cell without altering the genotype. Driven by internal signalling messages and external environmental cues
What are epigenetic tags?
Chemical modifications to DNA or histones that flag part of a genome to guide gene expression. Can be used to turn on or turn off a gene
What is DNA methylation?
The process of adding a CH3 methyl group to a DNA nucleotide as an epigenetic tag. Often added to the promoter region to prevent transcription and thus expression of a gene.
What is the importance of promoters in transcription?
Promoters are the binding site for transcription factors which allow RNA polymerase to bind. Indicate where new genes begin and regulate on/ off of the genes
What is the importance of transcription factors in transcription?
Transcription factors are proteins that regulate transcription. They can be general or specific (activators or silencers). Allow for precise and efficient regulation of genes.
What is the importance of an enhancer region in transcription?
A region away from the gene that has a binding site for activators to bind to. Allows DNA to form a loop, allowing activators to interact with transcription factors at the promoter to increase the rate of transcription
How can transcription factors be used to initiate transcription?
Activators are a type of transcription factor that can accelerate or promote transcription. Activators bind to enhancers
How can transcription factors be used to prevent transcription?
Repressors are a type of transcription factor that prevent or slow transcription by binding to the silencer region.
How is the length of the Poly A tail a form of gene regulation?
Changing the length of thr Poly A tail can alter the speed of degradation. By increasing the tail length, more of the protein is made before it is degraded, decreased tail length means faster degradation. External signals and chemicals can increase the rate of degradation also.
How does DNA methylation regulate transcription?
Methylation at the promoter region can regulate transcription by inhibiting the binding of transcription factors. Methyl groups can also bind to histones to silence multiple genes.
What is epigenetic inheritance?
Epigenetic inheritance is the process of some epigenetic tags being passed on to offspring. Therefore, the impact of environmental experiences can be passed on
What are primordial germ cells?
Diploid cells that go through meiosis to form gametes. Formed before an organism is born and have most of the epigenetic tags removed
What is epigenetic reprogramming?
The removal of epigenetic tags during the formation of primordial germ cells. This allows the zygote to access the full genome where epigenetic tags can be reprogrammed or edited
What are imprinted genes?
Tags added to genes in the process of becoming gamete cells. A gene that is only expressed/ silenced in one type of gamete (e.g sperm but not egg)
What are differentially methylated regions (DMR’s)?
Regions which have the same DNA base sequence, but different gene expression due to the accumulation of different methylation patterns
What is an operon?
ONLY IN PROKARYOTES. When several related genes share the same promoter. Allows groups of genes to be turned on/ off using an operator site that a repressor can bind to
How is air pollution linked to methylation?
Nitrous oxides and hydrocarbons in air pollution can decrease methylation, causing an increased expression of proteins that regulate the immune system. Causes excess inflammation leading to asthma and heart disease. More significant during pregnancy
Explain the example of ligers and tigeons as an example of epigenetic inheritance
Ligers (BIG)= male lions imprinted gene codes for larger offspring x Tiger (no imprinted gene)
Tigeons (SMALL)= female lions imprinted gene codes for smaller offspring x Tiger
How have monozygotic twin studies helped our understanding of methylation?
Monozygotic twins have the same DNA sequences (genome). But they present with different phenotypes, due to their accumulated methylation patterns over their lifetime
