typical and atypical mendelian inheritance Flashcards
a vertical pattern of inheritance would suggest?
autosomal dominant condition
why would you look for male-to-male transmission?
to establish if it is the X chromosome that is causing the issue
what is incomplete penetrance
inheriting a gene may not make it certain that you will be affected by a condition, only more likely
what is complete penetrance
If you inherit the mutation and get the disorder always it is complete. Achondroplasia has complete penetrance
what is gonadal mosaicism
where more than one set of genetic information is found specifically within the gamete cells
what pattern is seen in autosomal recessive inheritance
horizontal
give examples of autosomal recessive conditions
CF, PKU, congenital adrenal hyperplasia, spinal muscular atrophy
what risk do offspring of an affected adult have of developing an autosomal dominant condition ?
50%
what risk do offspring of an affected adult have of developing an autosomal recessive condition
very low (would need to have two parents with the faulty gene)
what major feature does X-linked recessive inheritance show
Knight’s move pattern
Can pass through unaffected females and onto a male.
what is an obligate carrier?
those who can be calculated to definitely be a carrier of the genetic condition
what percentage of a female carrier of an x-linked recessive condition son’s will be affected by the condition?
50%
what percentage of a female carrier of an x-linked recessive condition daughter’s will be carriers for the condition?
50%
what proportions of male offspring of a male heterozygote for an X-linked recessive condition will be affected
none
what proportions of daughter of a male heterozygote for an X-linked recessive condition will be carriers
all
give some examples of an X-linked recessive condition
- Red-green colour blindness
- Haemophilia A and B
- Duchenne muscular dystrophy
what pattern do you see in x-linked dominant conditions?
female to female, and female to male but no male to male
vertical pattern
give some examples of x-linked dominant condition
o Vitamin D resistant rickets
o Incontintentia pigmenti (has male lethality)
o Rett syndrome (male lethality – usually)
what proportion of daughters will be affected in male to female transmission in x-linked dominant conditions
all
what is genetic anticipation
give examples
genetic condition in which there is increasing severity and earlier age of onset with successive generations
Huntington’s disease, myotonic dystrophy and Fragile X syndrome
what is pseudo-dominant inheritance
Give an example
this is where there is a very high carrier frequency for a condition so on family tress it looks like autosomal dominant
Gilbert’s syndrome
