Module 3: Mendelian Inheritance Patterns

Question 1

Gene Disorder

Answer 1

• Caused by DNA changes in a specific gene - isn’t always just one
• Follow patterns of inheritance
• Can also be new & passed to children

Question 2

De novo

Answer 2

• New mutation in individual that was not in previous generation
• Usually either at the egg or sperm level or early in development

Question 3

4 Patterns of Inheritance

Answer 3

• Autosomal Dominant
• Autosomal Recessive
• Mitochondrial
• X-linked

Question 4

Autosomal Recessive Conditions

Answer 4

• Dominant allele is the wild type
• Recessive allele is mutated
• Only 1 normal copy of the normal allele is needed for normal function

Question 5

What is the % risk of an affected child if both parents are carriers for an autosomal recessive condition?

Answer 5

25%

Question 6

What is the % risk of an affected child if one parent is a carrier for an autosomal recessive condition?

Answer 6

0%

Question 7

Consanguinity

Answer 7

The increased chance of a recessive condition caused by reproduction between blood relatives

Question 8

Autosomal Dominant Conditions

Answer 8

• Dominant allele is mutated
• Only need 1 copy of the mutated gene to express the condition
• Homozygous mutations are often lethal or severe

Question 9

What is the recurrence risk for each child of an affected individual?

Answer 9

50%

Question 10

Dominant Negative Effect

Answer 10

The altered protein that is produced interacts abnormality with other normal proteins

Question 11

Haploinsufficiency

Answer 11

When a mutagen prevents the production of the full amount of proteins

Question 12

Gain of Function

Answer 12

Mutated protein has a different function that alters development

Question 13

X-linked Conditions

Answer 13

• Conditions caused by variants in genes on the X chromosome
• No male to male transmission, but usually affects males more
• Females can show clinical signs if both X’s are affected

Question 14

Mitochondrial DNA

Answer 14

• Maternal/powerhouse DNA

- Passed through egg only

Question 15

What is the chance for a couple to have an UNAFFECTED child if both parents are AR carriers of the same condition?

Answer 15

75%

Question 16

Consanguinity increases the risk for ___?

Answer 16

Autosomal recessive disorders

Question 17

What is the risk for an unaffected person with a family history of AD disease to have a child with the AD in the family?

Answer 17

0%

Question 18

What type of mutation causes a reduction in the amount of normal protein production?

Answer 18

Haploinsufficiency mutation

Question 19

Mr. Jones has X-linked hemophilia, what is the chance for him to have an affected son?

Answer 19

0%