Lecture 32. Genetics of Common Disease Flashcards
How does the inactivated x chromosome replicate and stay inactivated ?
Exists as the barr body and replicated at the s phase of mitosis
What are the markers used for linkage analysis ?
These markers are simply oligos, or synthetic strands of DNA that will bind to a specific sequence of DNA in the human genome
How do restriction enzymes recognise specific DNA sequences ?
The active site of the enzyme has a configuration that only allows a specific sequence of DNA to make correct contact. Once the correct sequence enters the active site, the enzyme changes conformation and breaks the DNA chain.
Why do BRAC1 and BRAC2 variants only affect breast/ovary tissue ?
They can lead to other cancers but promoters induce higher expression levels in these tissues
What is down syndrome caused by ?
A trisomy in chromosome 21
What are some signs and symptoms of down syndrome ?
- Craniofacial patterning
- Cognitive impairment
- Congenital heart defects
- Duodenal stenosis
- Megakaryocytic leukaemia
- Solid tumours are less common
What is Edward’s syndrome caused by ?
Trisomy 18
What are some clinical features of Edward’s syndrome ?
- Mental retardation
- Low birth weight
- Abnormally shaped head
- Clenched fists
- Heart defects
What is Patau syndrome ?
Trisomy 13 (mosiac)
What are some features of Patau syndrome ?
- Cleft lip/palette
- Clenched hands
- Close set eyes
- Poor muscle tone
- Polydactyly
- Low set ears
- Mental retardation
- Microcephaly
- Congenital heart disease
- Seizures
- Deafness
What is klienfelter syndrome ?
XXY - affects males, tutankhamen
What are some symptoms of klienfelter syndrome ?
- Tall, thin
- Infertile
- Mild to moderate breast development
- Sagging tummy
What is Turners syndrome ?
45XO
What are some signs of turner’s syndrome ?
- Webbing of neck
- Short stature
- Ovarian failure
What is triple X syndrome ?
XXX - maternal X chromosomes do not disjoin