Introduction to med gen Flashcards
(44 cards)
phenotype definition
the physical description of a character in an individual organism
genotype definition
the genes an individual has at a particular site or locus, responsible for the observed phenotype
penetrance definition
the chance that a given genotype will cause a particular phenotype, usually referring to the mutation
character definition
a structure, function or attribute determined by a gene of group of genes
trait definition
alternate forms of a character
locus definition
a location within the genome
consanguineous definition and appearance on pedigree
related couples that form offspring, double line
different twin types and their appearance on a pedigree
monozygotic, identical twins- line between them forming a triangle
dizygotic, fraternal twins- triangle with no bottom line
pregnancy appearance on pedigree
small triangle
name the 6 main modes of inheritance
autosomal dominant, autosomal recessive, X-linked recessive, X-linked dominant, mitochondrial, uni parental disomy
explain autosomal dominant
gene carried on the autosome and affects heterozygotes
3 examples of autosomal dominant conditions
Huntington’s disease, breast cancer, Marfan syndrome
explain autosomal recessive
gene carried on the autosome and only affects homozygotes with 2 copies of the mutated gene. Two carriers of the condition would result in a 25% chance of offspring having the condition
3 examples of autosomal recessive conditions
cystic fibrosis, sickle cell anaemia, albinism
explain X-linked recessive
in a woman, both Xs would need to carry the mutation to be affected, in the man only the X needs to be affected. Female carriers are usually unaffected due to X-linked inactivation
3 examples of x-linked recessive conditions
haemophilia, colour blindness, Duchenne muscular dystrophy
explain X linked dominant
if woman inherits one mutant X they will be affected but due to X-inactivation they will survive, men will die.
2 examples of x-linked dominant
Rett syndrome, hypophosphatemic Rickets
explain mitochondrial inheritance
DNA present within the mitochondria, which is inherited from the mother. Not all mitochondria carry the mutation, as the mutation load may very between egg cells, known as mitochondrial heteroplasty. Fathers cannot pass on mitochondrially inherited conditions. Mitochondrial DNA only encodes for mitochondrial proteins and all tRNAa.
2 examples of mitochondrial inheritance disease
MERRF, MELAS
Explain uni parental disomy
refers to the inheritance of two copies of one chromosome from one parent.
2 examples of uni parental disomy
Prader-Willi syndrome, angel man syndrome
when is uni parental disomy especially dangerous?
some genes are imprinted, meaning that we only use a specific gene from one parent and not the other. If the imprinted copy is not inherited, the gene is not expressed and the condition is present
What is Prader Willi syndrome?
fail to thrive until age of 3, after which they start to eat and their satiety sensor fails to work
