0305 Inherited Disorders Flashcards
What is an inherited disorder
An inherited disorder is a change in normal phenotype or function due to a faulty gene/s. Inherited disorders follow a family pattern of inheritence
Briefly describe simple mendelian inheritence ?
Mendelian inheritence describes the patterns of inheritence of diseases that can be modelled using dominant and recessive alleles
What is an allele
An allele is one of two or more versions of a gene (a segment of DNA that codes for a functional RNA or protein)
What is the ratio of phenotypic offspring of 2 heterozygotic parents of a dominant disease
3:1 (phenotype: no phenotype). The offspring can either be XX, Xx, xX or xx
What type of mendelian disease is cystic fibrosis
Cystic fibrosis is an autosomal recessive disease
What type of mendelian disease is huntington’s disease
Huntington’s disease is an autosomal dominant disease
What is a sex linked disease
A sex linked disease is a disease where the genotype resides on the sex chromosomes. Most sex linked disease are linked to the x chromosome
A disease is X-linked recessive. The father is affect (xY) while the mother is unaffected (XX). What phenotypes and sexes could the offspring potentially be?
xX = girl carrier xX = girl carrier YX = boy unaffected YX= boy unaffected
A disease is X-linked recessive. The father is unaffected (XY) while the mother is a carrier (xX). What phenotypes and sexes could the offspring potentially be?
YX = boy unaffected Yx = boy affected XX = girl unaffected Xx = girl carrier
A disease is X-linked dominant. The father is affected (XY) while the mother is unaffected (xx). What phenotypes and sexes could the offspring potentially be?
Xx = girl affected Xx = girl affected Yx = boy unaffected Yx = boy unaffacted
A disease is X-linked dominant. The father is unaffected (xY) while the mother is unaffected (Xx). What phenotypes and sexes could the offspring potentially be?
xX = girl affected xx= girl unaffected YX= boy affected Yx = boy unaffected
What is codominant inheritance? Give one example of codominant inheritance
Co-dominance inheritance is when contributions of both alleles are visible in the phenotype. There is at least one pair of alleles that is no dominant over the other. E.g. different blood types
List the antibodies present in the plasma of individuals with blood group A, B, AB and O
Group A = B antibodies
Group B = A antibodies
Group AB = no anitbodies
Group O = A and B antibodies
List the anitgens presented on RBC of individuals with blood group A, B, AB and O
Group A = A antigens
Group B = B antigens
Group AB = AB antigens
Group O = no anntigens
True or False - most known disease follow inheritence patterns of simple mendelian inheritence
False. Most disorders are not that simples
What are complex diseases
Complex diseases are influenced by combinations of factors such as genetics, environment and lifestyle
What are multifactorial disorders
Multifactorial disorders are disorders where more than one gene must be inherited to present with symptoms
What is concordance? What is disconcordance
Concordance = both twins developing the same trait. Disconcordance = both twims don’t develop the same trait
True or false: dizygotic twins (two eggs) have higher concordance than monozygotic twins (one egg)?
False. Monozygotic twins have higher concordance
Define heritability. Give an example of a disease with high and one with low heritability?`
Heritability is measure of the fraction of phenotype variability that is due to genetic variation (1 = likely due to genetic inheritance). E.g. autism has high heritability 1.0 where as measles has low inheritability 0.16
