Theme 1 - Intro to pathology and genetics Flashcards
____ is used for information transfer
RNA
____ is used for information storage
DNA
Why is RNA much more unstable than DNA?
RNA is transient (short lasting) because the -OH on C2 in RNA attacks the phosphodiester bond
What is the sense strand?
The strand that ends up in the mRNA
What is a synonym for the short arm of chromosome 7?
7p
What is a synonym for the long arm of chromosome 7?
7q
What are haploinsufficient genes? Which genes are haploinsuffient and which aren’t?
Genes that don’t tolerate the loss of one copy of the pair of chromosomes
All autosomes are haploinsufficient, sex chromosomes are not
What are pseudoautosomal regions?
homologous regions where identical genes are shared between X and Y
Are there more unique genes on the X chromosome or Y?
X chromosome
Very few unique genes on Y chromosomes
Give two features of mitochondrial DNA
Circular DNA not linear
Cytoplasmic DNA not nuclear
Maternal (oocyte inheritance)
What is satellite DNA?
Large blocks of repetitive sequences
What is the structure of a gene?
Lecture 1 page 6
What are the 5 steps for forming a protein?
- Transcription (RNA polymerase)
- Cleavage and Polyadenylation
- Splicing
- Translation
- Post translational modification
What is alternative splicing?
Most genes can encode more than one type of protein by using axons in different combinations
What are processed genes?
Intronless copies of other genes. Most are non functional
What is alphoid DNA?
- A type of satellite DNA found at centromeres
- required for assembly of the centromere
- repeat unit sequence shows chromosome specific sequence variation
What is a polygene?
A gene whose individual effect on a phenotype is too small to be observed, but which can act together with others to produce observable variation
What are the 5 classifications of genetic disorders
- Multifactorial - The interaction of multiple genes in combination with environmental factors e.g type II diabetes, ischaemic heart disease
- Single gene - mutation in a single gene (AD, AR, XL -mendelian inheritance) e.g cystic fibrosis
- Chromosomal - an imbalance or rearrangement in chromosome structure e.g aneuploidy, deletion, translocation
- Mitochondrial - mutation in mitochondrial DNA
- Somatic mutations - mutations within a gene in a defined population of cells that results in disease e.g breast cancer
What type of inheritance are myotonic dystrophy, Marfan syndrome and Huntington’s disease?
Autosomal dominant
What is penetrance?
The frequency with which a specific genotype is expressed by those individuals that process it, usually given as a percentage e.g Huntington disease by 80 years is 100% penetrance
What is incomplete penetrance?
Not all relatives who inherit the mutation develop the disorder e.g BRCA1 mutations 80% life time chance of developing breast cancer
What is expressivity?
Variation in expression - the extent to which a heritable trait is manifested in an individual
What is anticipation?
The symptoms of a genetic disorder apparent at an earlier age as it is passed from one generation to the next
This occurs in myotonic dystrophy and Huntington’s disease
What type of inheritance is CF, Haemachromatosis and sickle cell disease caused by?
Autosomal recessive