epigenetics Flashcards
define epigenetics
the control of gene expression by modifying DNA or histones but not effecting the DNA nucleotide sequence
what causes the changes in gene function
caused by variation in the environment such as duet of stress which alters the way a gene is expressed
what is the role of histones in epigenetics
they package DNA and help condense it into chromosomes
they are covered in chemicals called tags which accumulate through life forming an epigenome
what is an epigenome
a record of the chemical changes (tags) of DNA and histone proteins in an organism which determine the shape of the histone-DNA complex
outline epigenetic silencing
inactive genes which are tightly wrapped around a histone and become inaccessible ensuring they cant be transcribed
outline structure of active genes around the histone
genes are looser and more easily read allowing them to be transcribed
what is acetylation
the process which causes gene activation by causing DNA to become less tightly wound around DNA allowing transcription
what occurs if more aceyltation of histones happens
DNA becomes less tightly wound so more transcription occurs
how can epigenetics be controlled
1) increased methylation of DNA
2) decreased acetylation of associated histones
what does DNA methylation do
1) over methylation- more methyl groups added causing DNA to become more tightly wound around histones inhibiting transcription
2) under-methylation- associated with gene activation where fewer methyl groups so DNA is less tightly wound so it is easier for more transcription
what does epigenetics allow
the different expression of the same gene in different parts of the same organism for example X inactivation in female tortoiseshell cats which have a patchwork of fur color due to alternative x chromosome inactivation in different groups of cells
