inheritance of human disease Flashcards
what is a mendelian disorder
diseases that segregate in families. caused by a change in a single gene. high penetrance. X - linked.
what is penetrance
the extend to which a particular gene is expressed in the phenotype of an individual (how much it effects them)
what can having a dominant gene mean for inheritance of disease
you will pass on a faulty gene, child has 50% chance which gene they express. males and females at equal risk
what does having a recessive gene mean for inheritance of disease
2 faulty copies of gene needed to cause disease to child. often only 1 generation effected. limited risk to child
X linked inheritance
in terms of disease y chromosome is irrelevant. X has more genes than Y so more faulty genes occur on X.
how does x-linked inheritance effect female carriers children
half male children will be affected (as they could get either of the mothers X chromosomes). half the female children effected
how does x linked inheritance effect male carriers children
all male children will be normal as they don’t get the effected X chromosome. but all female children will be affected as they will definitely get the X chromosome
what is x inactivation
only one of the x chromosomes in each cell has to be activated otherwise it can negatively effect the female. so one x chromosome in each cell is turned off at random
how does x inactivation effect inheritance
this gives the female a 50/50 chance that the x chromosome carrying the defect will be turned off. meaning half cells will be normal, half will be effected
what are SNPs
single nucleotide polymorphisms. alterations in DNA that everyone has. some can make you more prone to disease, most are harmless
do environmental factors contribute to mendelian disorders
there’s small environmental contribution to these disorders
