Genetics 3 Flashcards
What is the transcriptome?
The sum total of all messenger RNA molecules expressed from the genes of an organism.
What is epigenetics?
The study of changes in organisms caused by modification of gene expression rather than the alteration of the genetic code itself.
What is genomic imprinting
Where the genome carries and imprint of its parental origin, for example an active maternal allele may be inherited with an inactive parental allele, so the maternal one is expressed.
How is DNA methylation important in genetics?
The addition of a methyl group to the 5’ position of the pyramidine ring of a cytosine. This process is important in imprinting and X-inactivation
Describe the inheritence pattern of genomic imprinting.
The offspring inherits the epigenetic modifications from the parents. These modifications are present throughout the somatic cell lineage, but in the germ cells genetic markers are cleared and reset. They are reset on the basis of whether the embryo is destined to be a mother or a father. This means maternally expressed genes in a male wont be expressed in that males offspring, as it will now be inherited as a paternal allele. Inheritence is therefore non-mendelian, often skipping a generation or passing down one parental line.
What are the traits of a genetic pedigree of maternal imprinting?
The gene is inactive if inherited from the mother.
- Offspring of females are healthy as the faulty gene is inactive (50% chance of being a carrier)
- Offspring of males are affected if they inherit the faulty gene (50% chance of being affected)
What are the two chromosome 15 imprinting disorders? Which is paternal, and which is maternal?
- Prader Willi Syndrome is paternal loss of function
- Angelman Syndrome is maternal loss of function
What are the symptoms of Prader-Willi Syndrome?
Obesity, mental impairment, behavioural problems, muscle hypotonia, delayed puberty and infertility. A short stature with small hands and feet.
How is Prader-Willi syndrome managed?
Diet restriction, exercise and hormone treatment both at puberty and to increase growth.
What are the symptoms of angelman syndrome?
Developmental delay, movement disorder, happy demeanor, short attention span, as well as some people experiencing seizures.
What is the treatment of Angelman syndrome?
There are symptomatic treatmens including use of anti-convulsants, physiotherapy and sommunication therapy. Patients affected have a normal life span.
How are mitochondrial disorders inherited?
They are inherited through females, and passed on to all children regardless of gender. The intesnity of the disorder depends upon heteroplasmy.
What is MELAS?
Mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes. This is a progressive disease that is ultimately fatal, causing muscle weakness, vomiting, seizures and dementia.
What is LHON?
Lebers Hereditary Optic Neuropathy. This is more common in males, causes degeneration of the retinal ganglion cells resulting in blindness.
How could mitochondrial disorders be treated?
Use of three parent babies with a second mother, whose oocyte is used but the nucleus is removed.
