Mendelian Inheritance

Question 1

What do disease associated mutations do

Answer 1

Alter protein function as it will have a non functioning or missing protein

Question 2

What causes sickle cell disease

Answer 2

Abnormal HB gene

Question 3

What type of inheritance does sickle cell disease show

Answer 3

Autosomal recessive

Question 4

Where is sickle cell disease most prevalent

Answer 4

Africa
Mediterranean
Middle-East
India

Question 5

What does SCD do to RBCs

Answer 5

Causes them to become sickle shaped which causes pain, tissue damage,infection and even death

Question 6

What kind of problems can SCD cause

Answer 6

Problems with anaesthesia

Also: severe pain, cold, dehydration, infections, jaundice, stroke, leg ulcers, eye problems and kidney problems

Question 7

In a family pedigree what shape are the boys

Answer 7

Square

Question 8

In a family pedigree what shape are the girls

Answer 8

Circle

Question 9

What is it called hen there is a risk of 0

Answer 9

Population risk

Question 10

What is the chance of having a carrier child when the mother and father are both carriers of an autosomal recessive disorder

Answer 10

1/2 (50%)

Question 11

What is the chance of having an affected child when the mother and father are both carriers of an autosomal recessive disorder

Answer 11

1/4 (25%)

Question 12

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)

Answer 12

2/3 (66%)

Question 13

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)

Answer 13

2/3 (66%)

Question 14

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)

Answer 14

1/3 (33%)

Question 15

What is the chance of having a carrier child when only one parent is a carrier of an autosomal recessive disorder

Answer 15

50%

Question 16

What is the chance of having an unaffected child when only one parent is a carrier of an autosomal recessive disorder

Answer 16

50%

Question 17

What is the chance of having an affected child when only one parent is a carrier of an autosomal recessive disorder

Answer 17

0%

Question 18

What can CF affect

Answer 18

Sinuses
Lungs
Skin
Liver
Pancreas
Intestines
Reproductive organs

Question 19

What happens to the airways in CF

Answer 19

Airway walls tend to have thick, sticky mucus which blocks the airway and they may have bacterial infections and blood in their mucus

Question 20

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

Answer 20

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

Question 21

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

Answer 21

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.

Question 22

What is the chance of a child being a carrier when the child’s maternal cousin (mother’s nephew) has CF

Answer 22

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

Question 23

What is the chance of having a carrier child when the father is a carrier of an autosomal dominant disorder

Answer 23

1/2 (50%)

Question 24

With autosomal dominant disorders can there be skipped generations

Answer 24

No

Question 25

Can there be male to male transmission in autosomal dominant conditions

Answer 25

Yes

Question 26

Is a male or female more likely to pass on autosomal dominant conditions

Answer 26

Equally transmitted by men and women

Question 27

What type of disease is Huntington’s disease

Answer 27

Autosomal dominant

Neurodegenerative

Question 28

What type of inheritance does Duchenne Muscular Dystrophy have

Answer 28

X-linked

Question 29

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

Answer 29

The sons will not have the condition

All of the daughters will carry the gene

Question 30

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

Answer 30

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

Question 31

Why are girls obligate carriers when the father has an X linked conditon

Answer 31

Because they must obtain an X chromosome from the father

Question 32

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

Answer 32

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

Question 33

Who does X linked inheritance classically affect

Answer 33

Males

Question 34

Can X linked inheritance skip generations

Answer 34

Yes

Question 35

What type of transmission cannot occur in X linked inheritance

Answer 35

Male to male

Question 36

Who can transmit conditions in X linked inheritance

Answer 36

Unaffected women

Affected men