Week 5- Genetic Disorders

Question 1

In a pedigree diagram how are males represented?

Answer 1

As squares (if they have the disease the square will be shaded)

Question 2

In a pedigree diagram how are females represented?

Answer 2

As circles (shaded if they have the disease in question)

Question 3

How are carriers represented in pedigree diagrams?

Answer 3

Half shaded square or circle, if X linked female carrier her circle will have a dot in the middle of it

Question 4

What is consanguinity?

Answer 4

Marrying first cousins

Question 5

On a family pedigree diagram, what indicates autosomal dominant inheritance?

Answer 5

One affected parent, both males and females affected, not all offspring affected

Question 6

On a family pedigree diagram, what indicates X linked recessive disorders?

Answer 6

Affected son but unaffected mother, not all gens affected, not all siblings being affected

Question 7

On a family pedigree diagram, what indicates mitochondrial inheritance?

Answer 7

Vertical transmission, all generations affected, inherited from affected mother

Question 8

On a family pedigree diagram, what indicates autosomal recessive inheritance?

Answer 8

Horizontal transmission, not all offspring effected

Question 9

What are some complicating factors for inheritance?

Answer 9

Age of onset: may be late eg Huntington’s so looks like there’s a gap in inheritance

Mt DNA changes over time: no of mitochondria affected changes, genomes mixed etc

Question 10

How is genetic risk calculated?

Answer 10

You start from the person with the known genotype and work downwards, then multiply the risks together. REMEMBER if the risks are dependent, omit genomes that are impossible eg if a person is affected by a dominant condition they won’t be homozygous recessive so they probability of them passing down the gene changes as options include DD/Dd not DD/Dd/dd