Genomic imprinting Flashcards
What type of cell do stem cells first differentiate into?
Progenitor cells
How are specific genes activated in specific cell types and not in others?
Transcription factors
Which type of cells have a haploid genome?
Sperm and egg (germ cells)
What type of cell is formed when two haploid cells fuse?
Diploid cells
How are haploid cells created from diploid cells?
The diploid cells divide by meiosis
Advantages of having two sets of genes?
Genetic diversity and a backup set
What did the cloning frogs experiment show?A
Each cell has the genetic information necessary to encode for a whole organism
What is the name for a cell containing two male prouclei?
Androgenetic
What is the name for a cell containing two female pronuclei?
Gynogenetic
What is a parthenogenetic embryo?
One oocyte that doubles its haploid genome to become diploid
Where can parthenogenesis occur?
Reptiles
What happens if two female pronuclei fuse instead of a male and a female?
No extra-embryonic tissue is formed
What happens if two male pronuclei fuse instead of a male and a female?
An excessive amount of extra-embryonic tissue and no embryonic tissue
What can maternal genes not form?
A placenta
What can paternal genes not form?
An embryo
What are hydatidiform moles?
Growths that occur in the ovum that occur instead of pregnancy
What causes hydatidiform moles?
Empty ovum (all genome is polar bodies and after fertilisation there is only a male contribution) or the ovum is fertilised by two sperm
What causes prader willi/angelman syndrome?
A deletion in chromosome 15
What condition comes about as a result of a deletion in the paternal chromosome 15?
Prader willi syndrome
What condition comes about as a result of a deletion in the maternal chromosome 15?
Angelman syndrome
Main symptoms of prader willi syndrome?
Obesity, metabolic issues
Main symptoms of angelman syndrome?
Growth retardation, underweight
What was observed after knocking a section of chromosome 15 out in male mice?
Male and female offspring had prader willi symptoms
What was observed after knocking a section of chromosome 15 out in female mice?
offspring were carriers
What are primordial gem cells?
Cells in the embryo that will become that organisms future gametes
When are imprints established?
After the primordial germ cells have migrated to the genital ridge
What are imprinting marks?
Methylation marks put on genes in primordial germ cells to help them differentiate into egg cells or sperm cells
What is different from imprinted genes to normal methylation on genes?
The imprint remains on some genes in the egg and sperm after fertilisation
What happens to imprinted genes during the development of the embryo?
They are read differently during the development of the embryo
In which cells in the embryo are imprinted marks erased?
The primordial germ cells
Which pronucleus is demethylated first?
The male
What has happened to the male pronucleus before any cell division has occured?
It has rapidly lost its methylation
What is responsible for the rapid demethylation of the male pronucleus?
TET enzymes
What happens to imprinted genes post fertilisation?
The imprints are maintained
Which type of epigenetic marks can be passed onto the next generation?
Imprinted marks
When are imprinted genes not resistant to demethylation?
Prior to fertilisation
What is the state of a gene on the opposite chromosome to the same gene that has been imprinted?
It is inactive
Why do imprinted genes share regulatory elements?
They occur in clusters
What is different between the imprinting control regions on different genes?
They are differentially methylated (i.e. one allele is methylated while the other isnt)
How many genes can an imprinting control region?
Multiple
What could happen if the imprinting control region at a certain locus is deleted?
All the imprinting at that locus may be lost
What is different between the two genes in a differentially methylated region?
The methylation and thus the chromatin conformation (methylated allele will have a more closed, compacted less accessible chromatin conformation than the unmethylated one)
Examples of genomic imprinting disorders?
Silver Russell and Beckwith Wiedemann syndromes, neonatal and maternal hypomethylation syndrome
What is x inactivation?
After fertilisation, when you have two x chromosomes one is inactivated
Difference between genomic imprinting and x inactivation?
Genomic imprinting is non-random whereas x inactivation is random
