Exercises Wednesday 17th of April, 2013
Basic genetics
Ex. 1)
a)
b)
c)
d)
e)
f)
g)
Where in the cell is DNA contained?
How many chromosomes does a human somatic cell have?
And how many does a gamete have?
What is meiosis?
Give three examples of types of human genetic variation, and explain what they are.
Which three characteristics make a variant suitable as a genetic marker?
Which factor(s) is/are important for deciding which approach to choose when doing
genetic mapping of disease?
Pedigrees and modes of inheritance
Ex.2)
John has an eye condition which runs in his family. He is married and has 3 children, Maya, Kate
and Greg. Kate has the eye disease as well, but both Maya and Greg seem to be fine. Greg has 2
children, Maya 1 and Kate has 6 children. None of the children seem to be affected.
a) Draw the family pedigree.
b) What seems to be the mode of inheritance in this family?
c) Why are none of Kate's children affected by the eye disease? (More than one answer
is possible.)
Ex. 3)
Elena and Tom have 7 kids together, of whom 2 boys are affected by a rare neurological
syndrome. Elena has 4 healthy siblings and Tom has 3 healthy siblings. All siblings have healthy
children. Elena's mother is the sister of Tom's father. They are both unaffected.
a) Draw the family pedigree.
b) What could be the mode of inheritance in this family?
Ex. 4)
Mary and Pete have 2 sons and a daughter. Their first born son is affected by a severe mental
retardation and epilepsy. Mary has 3 sisters who are healthy and Pete has 2 brothers who are
healthy. Both the parents of Mary and Pete are also unaffected.
a) Draw the family pedigree.
b) What could be the mode of inheritance / genetic mechanisms in this family? (More
than one answer is possible.)
c) In a consultation, Mary reveals that one of her sisters has two sons and one of them
also has severe mental retardation. Draw the pedigree.
d) If the ffected boy has a similar phenotype to his cousin, what is the most likely mode
of inheritance?
e) Draw the carrier symbol in the individuals most likely to be carriers.
f) It turns out that the two boys do have a similar phenotype, but only one of them has
epilepsy. How can this be? What are the possible explanations to this?