Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
14 Cards in this Set
- Front
- Back
|
Define the term epigenetics |
Stable changes in genome function that do not change the underlying DNA sequence. |
|
|
What are the 3 ways that genes can be switched on/off? |
1. DNA Methylation 2. Histone Modifications 3. microRNA additions |
|
|
Explain the process of DNA methylation |
1) DNA methyltransferase enzyme sticks a methyl group onto the nucleotide (usually promotor region - cytosine) 2) Enzymes are no longer able to stick to the DNA as the chain is no longer smooth so this prevents transcription of these areas. 3) If DNA is methylated upstream of a TATA box then that gene will not be expressed |
|
|
Explain the process of histone modification |
1) Histones are proteins that DNA wraps around to make chromatin. 2) They can be methylated or acetylated meaning that they are unable to be uncoiled and therefore DNA wrapped around them will not be transcribed. |
|
|
Explain how microRNA is involved in epigenetics |
1) microRNA is a small non coding RNA molecule 2) Silences complementary base pairs. 3) Strand of microRNA will attach to a specific gene via complementary base pairing 4) This will cause the RNA to cleave/ break into several pieces. 5)microRNA, tRNA, rRNA can all act in this way to silence genes |
|
|
What is priRNA What is preRNA |
priRNA: strand of RNA is able to fold back on itself to form priRNA preRNA: preRNA is cut using a 'dicer' enzyme to form smaller pieces around 20 nucleotides long. |
|
|
What is a bivalent domain? |
Bivalent chromatin is chromatin that contains both activating and repressing epigenetic modifications in the same area. This gives it stem cell like properties as it is 'poised'. The DNA will differentiate due the combinations of alleles that are finally activated/silenced. |
|
|
What happens to epigenetic markers during cell division? |
The marks are removed and propagated during cell division. Many enzymes exist to add/remove epigenetic marks eg.DNA methyltransferases, histone deacetylases. |
|
|
What is euchromatin? What is heterochromatin? |
Euchromatin: Accessible, malleable chromatin that is lightly packed and loosely coiled.
Heterochromatin: Inaccessible, restricted chromatin that is densely packed and tightly coiled. |
|
|
How is bisulphate sequencing used to study DNA methylation? |
Locations of methylated cytosine can be found by treating DNA with bisulphate. Unmethylated cytosine will be converted to uracil. Methylated cytosine will not be affected. DNA can then be analysed to work out where the cytosine (and therefore methylation) remains. |
|
|
How can chromatin immunoprecipitation be used to study histone modification |
Uses antibodies. Antibodies are very specific so can be used to isolate different modifications. Antibodies are used to precipitate out certain histone marks. After antibodies have separated histone proteins then the DNA of these can be looked at. |
|
|
What are the recent technological developments to do with DNA sequencing? |
Using machinery a human genome can now be sequenced in a few hours. High throughput sequencing is the technique that allows this to happen. |
|
|
Give some examples of epigenetic phenomena: |
1) In women the X chromosome is silenced. 2) At random in the cells of the body one allele (either from mother or father) is silenced. (If mothers is deleted child is bigger, if fathers is deleted child is smaller) 3) There are differences in phenotype due to epigenetic marks 4) Environmental factors can influence epigenetic marks, eg. body type of honey bees |
|
|
Does abberently marked epigenetics cause disease? |
1) Epigenetics are associated with all types of cancer 2) Epigenetic disregulation contributes to many other diseases. 3) Drugs are being developed and researched which hope to change abberent epigenetic marks back to the 'norm' |
