Pedigrees and Risk

Question 1

What is a pedigree chart?

Answer 1

A diagram which shows the presence or absence of a trait within a family across generations, used to analyse the pattern of inheritence through a family

Question 2

What symbol is used to show a male?

Answer 2

Square

Question 3

What symbol is used to show female?

Answer 3

Circle

Question 4

What is used to show a person who is affected?

Answer 4

Coloured in circle

Question 5

How is the difference between X linked Carrier and Autosomal carrier shown on a pedigree chart?

Answer 5

X linked carrier has a dot in the middle, autosomal has half the shape shaded

Question 6

How is a consanguineous couple shown on a pedigree chart?

Answer 6

Double lines connecting the male and female

Question 7

What is the difference between monozygotic and dizygotic twins?

Answer 7

Monozygotic are identical, dizygotic are not

Question 8

If only females pass it on, which type of inheritance is it likely to be?

Answer 8

Mitochondrial

Question 9

If only males are affected, which type of inheritance is it likely to be?

Answer 9

Y linked

Question 10

If unaffected parents can have affected children, is the pattern of inheritance for that condition likely to be dominant or recessive?

Answer 10

Recessive

Question 11

If affected parents can have unaffected children, is the pattern of inheritance for that condition likely to be dominant or recessive?

Answer 11

Dominant

Question 12

If the condition is more common in females, which type of inheritance does it tend to be?

Answer 12

X-linked dominant - affected males transmit to all daughters

Question 13

If the condition is more common in males, which type of inheritance is it likely to be?

Answer 13

X-linked recessive - affected females transmits to all sons

Question 14

Why is calculating risk useful?

Answer 14

It allows parents to make an informed decision as to whether they want to start a family or not given the risk of certain conditions

Question 15

Describe, in detail, the social and cultural issues related to stigma and bias that might impact upon their decision when deciding whether or not to start a family

Answer 15

A recognition that the couple might be hesitant to seek medical advice at this
point, due to a sense of shame/stigma surrounding sickle and a desire not to mark
oneself out as ‘different’ or ‘disadvantaged’ (1 mark).
Recognition of the potential unconscious bias of the medical professional when
carrying out a consultation (1 mark).
Mention of the historical roots of such stigma (1 mark).
Students might cite the scientific racism of the 19th century that argued for
quantifiable biological and anatomical differences between the black and white