Mendelian Inheritance Flashcards
What do disease associated mutations do
Alter protein function as it will have a non functioning or missing protein
What causes sickle cell disease
Abnormal HB gene
What type of inheritance does sickle cell disease show
Autosomal recessive
Where is sickle cell disease most prevalent
Africa
Mediterranean
Middle-East
India
What does SCD do to RBCs
Causes them to become sickle shaped which causes pain, tissue damage,infection and even death
What kind of problems can SCD cause
Problems with anaesthesia
Also: severe pain, cold, dehydration, infections, jaundice, stroke, leg ulcers, eye problems and kidney problems
In a family pedigree what shape are the boys
Square
In a family pedigree what shape are the girls
Circle
What is it called hen there is a risk of 0
Population risk
What is the chance of having a carrier child when the mother and father are both carriers of an autosomal recessive disorder
1/2 (50%)
What is the chance of having an affected child when the mother and father are both carriers of an autosomal recessive disorder
1/4 (25%)
What is the chance of being a carrier when your mother and father are both carriers of an autosomal recessive disorder and you know you do not have the disorder (e.g. 23 years old and have no symptoms of the disease)
2/3 (66%)
What is the chance of being a carrier when the mother and father are both carriers of an autosomal recessive disorder and you know you do not have the disorder (e.g. 23 years old and have no symptoms of the disease)
2/3 (66%)
What is the chance of being unaffected when your mother and father are both carriers of an autosomal recessive disorder and you know you do not have the disorder (e.g. 23 years old and have no symptoms of the disease)
1/3 (33%)
What is the chance of having a carrier child when only one parent is a carrier of an autosomal recessive disorder
50%
What is the chance of having an unaffected child when only one parent is a carrier of an autosomal recessive disorder
50%
What is the chance of having an affected child when only one parent is a carrier of an autosomal recessive disorder
0%
What can CF affect
Sinuses Lungs Skin Liver Pancreas Intestines Reproductive organs
What happens to the airways in CF
Airway walls tend to have thick, sticky mucus which blocks the airway and they may have bacterial infections and blood in their mucus
What is the chance of a child being a carrier if the grandparents are both carriers (and mother is definitely unaffected) and the father is from the UK where there is a 1/25 chance of being a carrier
The child’s mother’s chance of being a carrier is 2/3
The child’s father’s chance of being a carrier is 1/25
So the chance of both of them being a carrier is 2/3 x 1/25 = 2/75
So the child’s chance of being a carrier is 2/75 x 1/4 = 1/150
The child’s chance of being a carrier is 1/150
What is the chance of a child being a carrier if the grandparents are both carriers (and mother is definitely unaffected) and the father is from the UK where there is a 1/25 chance of being a carrier
The child’s mother’s chance of being a carrier is 2/3
The child’s father’s chance of being a carrier is 1/25
So the chance of both of them being a carrier is 2/3 x 1/25 = 2/75
So the child’s chance of being a carrier is 2/75 x 1/4 = 1/150
The child’s chance of being a carrier is 1/150.
What is the chance of a child being a carrier when the child’s maternal cousin (mother’s nephew) has CF
The child’s mother chance of being a carrier is 1/2 (as she either is a carrier or not and she definitely does not have the disease)
The child’s father is ignored in this situation as it is very unlikely he has the disease
So the child’s chance of being a carrier is 1/2 x 1/2 = 1/4
What is the chance of having a carrier child when the father is a carrier of an autosomal dominant disorder
1/2 (50%)
With autosomal dominant disorders can there be skipped generations
No
Can there be male to male transmission in autosomal dominant conditions
Yes
Is a male or female more likely to pass on autosomal dominant conditions
Equally transmitted by men and women
What type of disease is Huntington’s disease
Autosomal dominant
Neurodegenerative
What type of inheritance does Duchenne Muscular Dystrophy have
X-linked
In X-linked inheritance, if the father is affected by a condition and the mother is not, what is the likely outcome for their children
The sons will not have the condition
All of the daughters will carry the gene
Why is it that in X-linked inheritance, when the father is affected by the condition the sons have only a population risk of obtaining the disorder
Because the mutation present in the father is on the X chromosome and the son is only obtaining the Y chromosome from the father and X from the mother
Why are girls obligate carriers when the father has an X linked conditon
Because they must obtain an X chromosome from the father
In X-linked inheritance, if the mother is affected by a condition and the father is not, what is the likely outcome for their children
1/2 chance of a child having the disease when the sex is known
1/2 chance of the daughter being a carrier
1/4 chance of when the sex is unknown
Who does X linked inheritance classically affect
Males
Can X linked inheritance skip generations
Yes
What type of transmission cannot occur in X linked inheritance
Male to male
Who can transmit conditions in X linked inheritance
Unaffected women
Affected men
